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    15 December 2004, Volume 15 Issue 12
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    Soil quality assessment of forest stand in different plantation esosystems
    HUANG Yu, WANG Silong, FENG Zongwei, GAO Iong, WANG Qingkui, HU Yalin, YAN Shaokui
    2004, (12):  2199-2205. 
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    After a clear-cutting of the first generation Cunninghamia lanceolata plantation in 1982,three plantation ecosystems,pure Michelia macclurei stand (PMS),pure Chinese-fir stand (PCS) and their mixed stand,were established in spring 1983,and their effects on soil characteristics were evaluated by measuring some soil physical,chemical,microbiological and biochemical parameters.After 20 years' plantation,all test indices showed differences among different forest management models.Both PMS and MCM had a favorable effect on soil fertility maintenance.Soil quality assessment showed that some soil functions,e.g.,water availability,nutrient availability,root suitability and soil quality index were all in a moderate level under the mixed and pure PMS stands,whereas in a relatively lower level under successive PCS stand.The results also showed that there existed close correlations between soil total organic C (TOC),cation exchange capacity (CEC),microbial biomass-C (Cmic) and other soil physical,chemical and biological indices.Therefore,TOC,CEC and Cmic could be used as the indicators in assessing soil quality in this study area.In addition,there were also positive correlations between soil microbial biomass-C and TOC,soil microbial biomass-N and total N,and soil microbial biomass-P and total P in the present study.
    Population structure and distribution pattern of rare plant communities in Houhe Nature Reserve
    DANG Haishan, JIANG Mingxi, TIAN Yuqiang, HUANG Handong, JIN Xia
    2004, (12):  2206-2210. 
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    An investigation on the size structure and spatial pattern of 26 major tree species with a diameter at breast height (DBH) ≥5 cm was made on a 1 hm2 fixed plot in the mixed evergreen and deciduous broad-leaved forest in Houhe National Nature Reserve of Central China.The results showed that 7 populations of the 26 species,i.e.,Dipteronia sinensi,Aesculus wilsonii,Pterostyrax psilophyllus,Davidia involucrate,Euptelea pleiosperma,Tetracentron sinense and Cercidiphyllum japonicum,were rare endangered species,and two of the 7 populations,T.sinense and C.japonicum,were very limited in numbers.The population structure of P.psilophyllus was in declining,and that of the rest was in growing.The spatial distribution pattern of P.psilophyllus,/i>A.wilsonii and T.sinense was in random,and that of the others was clumped.Among the other 19 non-rare populations,the population structure of P.wilsonii was in declining,that of D.lotus,A.palmatum,A.wilsonii,A.franchetii,M.cuneifolia and H.dulcis was stable,and the rest was in growing.The spatial distribution pattern of D.lotus and H.dulcis was in random,and that of the others was clumped.On the whole,the growing populations were dominant,amounting to 61.54%,and the stable and declining populations accounted for 6.92% and 11.54%,respectively.The results of the two judging methods were consistent,showing that the distribution pattern of clumping (80.77%) was dominant,while the random and even distribution patterns were infrequent.
    Biomass distribution patterns of Alnus hirsuta and Betula platyphylla-swamp ecotone communities in Changbai Mountains
    MU Changcheng, WAN Shucheng, SU Ping, SONG Hongwen, SUN Zhihu
    2004, (12):  2211-2216. 
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    In order to reveal the growth patterns of dominant tree species and the distribution patterns of community biomass along the horizontal environmental gradients or among the vertical layers of communities in Changbai Mountains,this paper studied the biomass distribution patterns of Alnus hirsuta-swamp and Betula platyphylla-swamp ecotone communities.The results showed that there were some differences in growth rate and in adaptability to habitats between A.hirsuta and B.platyphylla.In the wetland habitats of the ecotone,A.hirsuta grew 1～2 times faster than B.platyphylla,but along the gradient from swamp to forest,it grew slowly,while B.platyphylla grew fast.Therefore,A.hirsuta was a favorite tree species in wetland habitats.The distribution pattern of organ biomass was similar between A.hirsute and B.platyphylla,the trunk being 1/2,tree root 1/4,branch 1/10,bark 1.5/20,and leaf 1/20.The vertical distribution pattern of biomass was also similar between A.hirsute-swamp and B.platyphylla-swamp ecotone communities,the tree,shrub,and herbage layer accounted for 87%～90%,7%～9%,and 2%～3%,respectively in the whole ecotone communities.The community biomass increased linearly from swamp to forest with the change of environment factors.
    Position of Betula ermanii population ecotone in Changbai Mountains
    ZOU Chunjing, WANG Xiaochun, HAN Shijie
    2004, (12):  2217-2220. 
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    The vegetation on the northern slope of Changbai Mountains forms a vertical zone due to the vertical differentiation of moisture and heat conditions.Ecotones are obviously existed between different vegetation zones,but it is difficult to decide their positions.In the area from 1 400 m to 2 200 m elevation,we adopted the methods of gradient sampling,fractal analysis,population pattern analysis,and interspecific competition index analysis to describe Betula ermanii population ecotone.The results showed that there was a forest ecotone between Betula ermanii and Picea-Abies forest near elevation 1 650 m,and there was a forest line ecotone between Betula ermanii and alpine tundra near elevation 2 080 m.
    Major features of decline of Pinus sylvestris var.mongolica plantation on sandy land
    WU Xiangyun, JIANG Fengqi, LI Xiaodan, XUE Yang, QIU Sufen
    2004, (12):  2221-2224. 
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    In view of the decline of man-made sand-fixation forest of Pinus sylvestris var.mongolica in Zhanggutai sand land of Liaoning Province,this paper studied the major characteristics of the decline.The appearance of the declining man-made sand-fixation forest of Pinus sylvestris var.mongolica was grey green,its needle leaf was very thin,the blooming and fruiting rate was low,the average quantity of cones per tree was only 10.4～16.5,with only 6.96g to 7.39 g per thousand seeds,and there were many empty and astringent seeds.The seasonal dynamics of nutrients in 2-year-old pine needle leaf was similar,i.e.,the N and P contents decreased,while K content increased,showing that the nutrient cycle was imbalance.The chlorophyll content in 2-year-old needle leaf of declined forest was high,while that in 1-year-old healthy forest was also high but with a wide increasing range.The infected harm of shoot blight was the clearest mark to the decline of man-made sand-fixation forest of Pinus sylvestris var.mongolica.After the forest declined,the height and the DBH of the pine trees decreased evidently,and the structure of DBH distribution moved “left".The quantity of weak pine trees increased by 15.9%～27.2%,the roots decreased by 22.9%～28.9%,and the absorbing roots (diameter <0.5 cm) decreased most seriously.
    Decline regularity and causes of Pinus sylvestris var.mongolica plantation on sandy land
    WU Xiangyun, JIANG Fengqi, LI Xiaodan, XUE Yang, QIU Sufen
    2004, (12):  2225-2228. 
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    The study showed that the decline of Pinus sylvestris var.mongolica plantation out of its natural distribution area was a phenomenon of premature senility.The infected harm of shoot blight was the direct cause of Pinus sylvestris var.mongolica dying,but wasn't the basic reason.The decline of Pinus sylvestris var.mongolica was caused by the interaction of biological and other factors,which was "the third disease" beyond infectious and noninfectious diseases,namely,"decline disease of forest".Climate difference,improper management,unbalanced usage of soil water,and high content of N settled from air were the inducing factors,among which,climate difference and unbalanced usage of soil water were the main ones,while insect harm and shoot blight were the promoting factors.
    Effects of light and temperature on seed germination of Picea asperata and Betula albo-sinensis
    WU Yan, LIU Qing, HE Hai, LIN Bo, YIN Huajun
    2004, (12):  2229-2232. 
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    The effects of different light and temperature conditions on seed germination of two keystone species (Picea asperata and Betula albo-sinensis) in subalpine coniferous forests were studied by simulating environmental conditions in climatic chambers.The results indicated that the optimal temperature of seed germination for both species was 25 ℃,with the germination rate of 88.8±8.4% and 30.8±10.4%,respectively.Through multiple comparisons with Tukey's HSD,B.albo-sinensis was more sensitive to temperature than P.asperata.Seeds of P.asperata could germinate when the temperature reached 10 ℃,but those of B.albo-sinensis could not,which implied that the latter as a pioneer species of subalpine coniferous forest areas needed higher lowest temperature for seed germination.Day and night temperature difference (15 ℃/10 ℃,20 ℃/15 ℃ and 20 ℃/10 ℃) had significant effect on the germination rates of tested seeds,which was the highest under 20 ℃/15 ℃.A wide range of day and night temperature difference seemed to be unfavorable to the seed germination of B.albo-sinensis.Light intensity also had a marked effect on the germination rates of test seeds.Under 20% transmittance,the germination rate of P.asperata and B.albo-sinensis was the highest,being 83.0±6.6% and 29.2±5.5%,respectively,and the initiation time and regularity of germination were the best as well.Furthermore,B.albo-sinensis was less sensitive to light than P.asperata,which was determined by the life behavior of tree itself.
    Effects of 6-BA and AsA on photosynthesis photoinhibition of attached poplar leaves under osmotic stress of root
    FENG Yulong, MA Yongshuang, FENG Zhili
    2004, (12):  2233-2236. 
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    In order to know more about the relationships between photosynthesis photoinhibition and reactive oxygen species metabolism,the effects of 6-benzyladenine (6-BA) and ascorbate (AsA) on net photosynthetic rate (Pn),apparent quantum yield (AQY),superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities,O2-? generation rate,and H2O2 and malondialdehyde (MDA) contents were studied with attached leaves of poplar clone seedlings under osmotic stress of root.Under osmotic stress,the photosynthesis photoinhibition of attached poplar leaves,judged by the significant decrease of Pn and AQY,was aggravated,and the balance of reactive oxygen species metabolism was destroyed.The superoxide dismutase (SOD) activity increased,but ascorbate peroxidase (APX) activity decreased.In the meantime,the O2-? generation rate and the contents of H2O2 and malondialdehyde (MDA) increased.When osmotic stressed poplar seedlings were pretreated with 6-BA and AsA,the activities of SOD and APX increased,O2-? generation rate and H2O2 and MDA contents decreased,and photosynthesis photoinhibition was alleviated.The contents of reactive oxygen species and MDA in poplar leaves were negatively correlated with net photosynthetic rate and apparent quantum yield.It's indicated that the photosynthesis photoinhibition of attached leaves of poplar clone seedlings had intrinsic relations with the accumulation of reactive oxygen species under osmotic stress of root,and the alleviation effects of 6-BA and AsA on photosynthesis photoinhibition were related to their promotion effects to the scavenging system of reactive oxygen species.
    Effect of soil water potential on hydraulic parameters of Fraxinus mandshurica seedlings
    CUI Xiaoyang, SONG Jinfeng, QU Minghua
    2004, (12):  2237-2244. 
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    In this paper,soil water potential was controlled in the ranges of 0～-20 kPa(W1),-20～-40 kPa (W2), -40～-60 kPa (W3),-60～-80 kPa (W4) and -80～-160 kPa (W5) by a suite of specially designed root-sphere osmotic irrigation technique,and the dynamics of transpiration,water suction,tissue water potential and hydraulic resistance of Fraxinus mandshurica seedlings grown under these soil water conditions were studied.The results indicated that under sub-saturated soil water condition (W1),fine root water potential fluctuated at high levels from -0.08 MPa to -0.19MPa,which brought about the lowest soil-root hydraulic resistance (35.52 MPa·s-1·m-2·mol-1 in diurnal average),the highest water suction rate (4.44 mmol·m-2·s-1 in average from 10:00 to 14:00),and the strongest transpiration rate (5.11 mmol·m-2·s-1 in average from 10:00 to 14:00).Under field capacity (W2),soil-root hydraulic resistance increased several times above that under W1,water suction rate and transpiration rate declined significantly,while the diurnal single-peak pattern of transpiration was not altered.Under orderly increased soil water stress (W3～W5),soil-root hydraulic resistance (the average from 10:00 to 14:00) increased approximately 10～24 times above that under W1,which caused the consequent low water suction rate and low fluctuation levels of leaf water potential (-1.25 MPa～-1.94 MPa for W5),and transpiration was seriously restricted (the transpiration rate being only 0.91～1.55 mmol·m-2·s-1 at midday for W3～W5).It is concluded that soil water was not equally available to Fraxinus mandsharica seedlings in the test ranges of soil water potential,and significant water stress could occur when the soil water potential was lower than-40 kPa.
    Photosynthetic characteristics of main urban forest species Syringa oblata in Shenyang
    LI Haimei, HE Xingyuan, CHEN Wei
    2004, (12):  2245-2249. 
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    Using LI-6400 CO2 gas analysis system and by the methods of correlation analysis and multinomial regression, this paper studied the diurnal changes of Syringa oblata photosynthesis during different seasons and assessed the correlation between net photosynthetic rate and environmental factors. The results indicated that the photosynthetic rate showed a double-peak curve in spring and summer and a single peak curve in autumn. The major factors affecting the photosynthetic rate were the solar radiation and stomatal conductance in spring and summer, and the stomatal conductance and intercellular CO2 intensity in autumn. The related equation was also constructed in this paper.
    Dynamics of nutrient element iron in soil-plant ecosystem of the Songnen Plain Leymus chinensis grassland
    ZHOU Xiaomei, GUO Jixun, ZHAO Jiang
    2004, (12):  2250-2254. 
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    The study showed that in the soil-plant ecosystem of the Songnen Plain Leymus chinensis grassland,the contents of total and available iron in soil were relatively low,while Leymus chinensis was abundant in iron.The concentrations of soil total and available iron decreased with soil depth.Soil available iron positively correlated with soil organic matter,while negatively correlated with soil pH.The dynamics of soil total iron showed a “V" curve during the growth season,with the lowest in July,and that of soil available iron was similar to soil total iron from May to August,and gradually decreased after August.The iron concentration in Leymus chinensis changed dramatically with the trend of root>rhizome>leaf> litter >stem.The iron concentrations in leaf and stem had a fluctuant decrease,while those in root,rhizome and litter were fluctuated in “V" curve.Soil A layer enriched in a little more available iron.The iron activation with an average of 0.64% increased from May to August,and decreased after August,with the lowest in October.The shift ratio from underground to aboveground part of Leymus chinensis dropped during May-July,went up in August,and then dropped again.The average shift ratio from aboveground part to litter was 105.0%,which negatively correlated with that from underground to aboveground part.
    Changes of soil chemical properties in sheep urine patches in Inner Mongolia steppe
    LIU Zhongkuan, WANG Shiping, HAN Jianguo, WANG Yanfen, CHEN Zuozhong
    2004, (12):  2255-2260. 
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    Sheep play an important role in the nutrient cycling in extensively grazed grasslands,mainly through their annual return of around 5～25 kg N in the shape of urine.This return changes the temporal distribution of nutrients in soil and alters their bioavailability.Urine patches are the most important areas of the transformation and cycling of nutrients in the grazed grasslands.In order to make known the changes of soil chemical properties in sheep urine patches,an experiment was set up in the typical steppe area of central Inner Mongolia.The results indicated that soil pH value reached the maximum on the second day after urine excretion,and then declined.It maintained at around 6.5 from the 58th day,which was under the level of the control.Soil dissolved organic carbon (DOC) in urine patches exhibited the identical changing characteristics with soil pH,and had a significantly (P<0.01) positive correlation with it.Soil total dissolved phosphorus (TDP) increased significantly (P<0.05) after urine excretion,and reached the maximum at the 2nd day.The percentage of molybdate reactive phosphorus (MRP),dissolved organic phosphorus (DOP) and dissolved condensed phosphorus (DCP) showed significantly two changing phases,and there existed significantly (P<0.05) negative correlations between MRP,DOP and DCP.Soil NH4+-N reached the maximum on the 2nd day after urine excretion and then declined,while soil NO3--N increased significantly after 14 days and reached the maximum on the 21st day,showing significant “double peaks” characteristics.Soil dissolved organic nitrogen (DON) also increased significantly after urine excretion.
    Changes of four common plant populations growth and their anti-oxidative enzymatic system in desertification process
    ZHU Zhimei, YANG Chi
    2004, (12):  2261-2266. 
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    This paper studied the changes of the growth and anti-oxidative enzymatic system of four common plant populations during the desertification process of sandy grassland.The results showed that in the process of desertification,the individual height and density and the density percentage of the populations all had a decreasing trend.The growth of Melilotoides ruthenica was more vigorous before moderate desertification (MD) stage,but restricted after that.In MD stage,the growth of Leymus chinensis was heavily restricted,and its individual height,density and density percentage accounted for 57.19%,2.50% and 6.22% of those in original vegetation (OV) stage,respectively.The individual height and density of Cleistogenes squarrosa and Artemisia frigida increased in the stages of potential desertification (PD),light desertification (LD) or MD because of their phase status of dominant species and their stronger stress resistance.The SOD and POD activities of the common plant populations increased in PD and MD stages,but decreased in LD and heavy desertification (HD) stages.The CAT activity of Leymus chinensis was higher,whose response to desertification was not significant (P>0.05),and that of Melilotoides ruthenica increased significantly in PD and HD stages (P≤0.01).The activities of the three anti-oxidative enzymes in the common plant populations,except the CAT activity of Melilotoides ruthenica,decreased in HD stage.The MDA content in the common populations increased firstly,then decreased,and finally increased from OV to MD stage,and had a significant difference in different desertification gradients (P≤0.05).Based on the integrated analysis of the ecological and physiological changes,it could be concluded that Leymus chinensis was more sensitive to desertification,while Melilotoides ruthenica had a stronger bioenergy.
    Effects of grazing on architecture and small-scale pattern of grasses on artificial grassland in subtropical zone
    BAO Guozhang, KANG Chunli, GUO Ping
    2004, (12):  2267-2271. 
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    This study was conducted on a 5-year artificial grassland in subtropical zone of South China.The main types of established artificial grassland there were Dactylis glomerata-Lolium prenne-Trifolium repens and D.glomerata-T.repens pastures. Four grazing intensities were designed,i.e.,CK(no grazing),G1 (6 adult sheep·hm-2), G2(7.5 adult sheep·hm-2) and G3 (10 adult sheep·hm-2),and all the grazing plots were rotationally grazed. The architecture and small-scale pattern of grasses on the grazed and ungrazed grassland were discussed. After a period of 5-year grazing, the plant basal width and sward height of D. glomerata and T. pratense decreased gradually. In treatments CK,G1,G2 and G3,the basal width of D. glomerata was 6～8,2～4,0～2 and 0～2 cm, and that of T. pratense was 1～1.2, 6～8, 4～6 and 2～4 cm, respectively. The tuft density of D. glomerata in treatments CK, G1, G2 and G3 was 60, 95.1, 210.2 and 160 tufts·m-2, respectively. The tiller number per plant of D. glomerata decreased, while its tuft density increased significantly due to the increased grazing intensity. With the increase of grazing intensity, the internode length of T. repens decreased, while its branching angle increased. The average internode length in treatments CK, G1, G2 and G3 was 2.04, 1.69, 1.64 and 1.51 cm, while the branching angle was 46.5, 65, 73 and 77.3°, respectively. The average leaf density of T. repens in treatments CK, G1, G2 and G3 was 2.9, 13.0, 4.7 and 1.0·m-2, while the relevant stolon density was 19.9, 101, 142 and 82.6 m·m-2, respectively. Under moderate grazing intensity, both the leaf and stolon densities of T. repens increased. The main scale on small pattern of D. glomerata, T. repens and T. pratense was 2 cm×2 cm, which was further decreased under higher grazing intensity in the treatments of D. glomerata and T. pratense. Considering the heterogeneity of environmental resources, the change of the architecture and small-scale pattern could be regarded as an adaptation of grasses under grazing disturbance.
    Snow disaster in Aletai Region—Its remote sensing monitoring model and evaluation method
    LIANG Tiangang, GAO Xinhua, LIU Xingyuan
    2004, (12):  2272-2276. 
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    In this paper,a monitoring model of snow depth was built based on the 4 scenes of NOAA satellite digital images under sunshiny condition and the corresponding ground observation data from20 meteorological stations during 2 snow disasters from 1996 to 1997 in North Xinjiang.The pixel-based snow coverage rate and snow spatial classification were studied by using linear mixture spectrum disassembling method,and two grid data layers based quantified indices used for estimating snow hazard grade of grassland and animal husbandry were put forward.The results indicated that by using the snow monitoring model and linear mixture spectrum disassembling method,the image cell based snow depth and snow coverage rate could be calculated,and the precision of snow classification could be improved.The image cell based snow hazard index could systematically express the spatial distribution of snow,grass,animal and climate conditions,and reflect the snow hazard grade of grassland and animal husbandry.
    Relationships between biochemical qualities of paddy rice and climate conditions in the Anning River Valley
    PENG Guozhao, BAI Jian, WANG Jingbo
    2004, (12):  2277-2281. 
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    Base on the experimental data of paddy rice planted geographically periodically without control in the Anning River Valley of Sichuan Province,this paper quantitatively analyzed the effects of meteorological conditions from 40 days before heading to ripeness on the biochemical qualities of paddy rice,and developed a model about the integrated relationships between biochemical qualities of paddy rice and mean temperature,daily range of temperature and daylight hours,which would be of significance both for the instruction of paddy distribution in the Anning River Valley and for improving rice qualities via adjusting planting time.The results showed that climate conditions had a great effect on the biochemical qualities of paddy rice,which was different in ways and in critical periods.The period when the correlation between some ingredients of rice and climate conditions was most significant was before or after,or from before to after full heading,which widened the existing knowledge about the period which was important for paddy rice qualities forming.Applying this finding in the Anning River Valley during 2002～2003,the accumulated high-grade paddy farming area stood at 73 000 hm2,30 000 hm2 more than that in 2001,and brought 0.2 billion yuan increament to the peasants,promoting the development of high-grade paddy greatly.
    Effects of small amount precision seeding on winter wheat yield
    WU Dongbing, CAO Guangcai, LI Rongqi, ZHANG Zhongqi, QUAN Ming
    2004, (12):  2282-2286. 
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    A two-year autumn seeding experiment was conducted during 2001～2003 in Beijing to study the effects of small amount precision seeding on winter wheat yield.When the seeding amount was 22.5 kg·hm-2,the best average yield of winter wheat varieties DS No.1 and Linkang No.1 was 6 836.25 and 7 353.75 kg·hm-2,respectively,and some experimental plots had a yield surpassed 7 500 kg·hm-2.The test varieties had a normal expression of growth and development in their growth period,and the contents of total saccharide,proline and lysine in seedlings were higher,and the tillering ability of plant was stronger than the control.The net photosynthesis and transpiration rates,RS,COND and CINT of flag leaf showed the vigorous physiological functions of the plants,and the higher activities of nitrate reductase and SOD showed their stronger metabolism activity.There were more spikes per plant for the test varieties.In practicing small amount precision seeding,variety selection is the prerequisite,and sowing amount is the heart of the matter.
    Relationships between water-stable aggregates and nutrient status in black soil after reclamation
    YU Wantai, SHEN Shanmin, ZHANG Lu, MA Qiang, ZHAO Shaohua
    2004, (12):  2287-2291. 
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    The study on the dynamics of water-stable aggregates in black soil after reclamation and its relation to soil nutrient status showed that the contents of soil water-stable aggregates decreased significantly at initial reclamation stage,but the declining became small with time. >0.25 mm water-stable aggregates had a significant correlation with soil organic C,total N,total P and CEC,the correlation coefficients being 0.7625,0.6794,0.6084 and 0.8134,respectively,and also had a significant correlation with soil exchangeable Ca,Mg,K and Na.A closer relationship of the aggregates was found with soil organic C and CEC than with other fertility properties,while no evident correlation was existed between the aggregates and soil total K,available P,available K and slow-release K.In order to maintain a good aggregate structure of black soil,it is of most importance to concern a proper balance of soil organic C.
    Effects of land use and vegetation restoration on soil quality in a small catchment of the Loess Plateau
    GONG Jie, CHEN Liding, FU Bojie, LI Yanmei, HUANG Zhilin, HUANG Yilong, PENG Hongjia
    2004, (12):  2292-2296. 
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    Soil quality improvement plays an important role in sustaining global biosphere.This paper studied the changes of soil quality after 25 years' land use and vegetation restoration at the Anjiapo catchment of western Loess Plateau.The analyses of soil characteristics of wasteland,almond land,farmland,pineland,shrub land and fallow land showed that different land use and vegetation restoration had different effects on soil integrated fertility index.Soil organic matter content was increased due to planting shrubs and forests.Both vegetation restoration and fallow could improve soil quality.Cultivation practice could decrease soil nutrient levels,and cropland soil was degraded.Shrub soil formed “fertile island” in the semi-arid region.Fallow could improve soil fertility to some extent.Human activities and vegetation restoration could affect soil nutrient contents after land use pattern was changed.With the launch out into the “Grand development of Western China”,“Grain for Green Project” and ecological restoration,both shrub planting and fallow(natural restoration)should be the optional choices to restore soil fertility,as they could decrease soil erosion and improve soil condition at catchment scale,especially in the hilly and gully loess area.Integrative control of small catchment may be the best way for the sustainable development of the semi-arid hilly area of Loess Plateau.
    Dynamic analysis of land use and land coverage in mid-eastern China during 1988～2000
    TIAN Ziqiang, ZHENG Binghui, WANG Wenjie, LI Zicheng
    2004, (12):  2297-2303. 
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    Using remote sensing(RS) and geographic information system(GIS) technologies and based on the documentary and field sampling data,this paper constructed and analyzed the 1988 and 2000 landscape maps of mid-eastern China.The mapping area of mid-eastern China was about 2.87?106km2.With the rapid increase of economy and population,the area of farmland and town in mid-eastern China increased 10.921?105hm2 and 13.754?105 hm2,accounted for a 2.14% and 19.25% increase,respectively from 1988 to 2000.At the same time,the forest area decreased 17.83?104hm2,declined by 1.12%,because of the increasing demand for lumber provision and reclamation.The meadow area in 2000 increased 19.287?105 hm2,ascending 7.75%,while the coverage and quality of grassland declined,owing to the deteriorating environment.The untilled land in 2000 dropped 34.31%,contrast with 1988 by the reason of a large number of lands being exploited.
    Interactions between fungal-feeding nematodes and fungi and their effects on soil nitrogen mineralization
    LI Huixin, MAO Xiaofang, HU Feng, MA Jiping
    2004, (12):  2304-2308. 
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    A species of fungal-feeding nematodes (Aphelenchus avenae) and two species of fungi (Micheli corticolus and Moniliaceae sp.) were isolated from an alluvial soil planted with paddy-rice and wheat in subtropical region.In order to approach their interactions and effects on soil nitrogen mineralization,a gnotobiotic microcosm experiment was carried out with four treatments,i.e.,1) soil + fungi-I (M.corticolus),2) soil + fungi Ⅰ + Aphelenchus avenae,3) soil + fungi II (Moniliaceae sp.),and 4) soil + fungi Ⅱ + Aphelenchus avenae at 22 ℃ for 25 days.The results showed that the individuals of nematode and fungi were increased simultaneously,suggesting that the inoculation of A.avenae stimulated the growth of fungi.The fungal-feeding nematode increased during the initial 20 days of incubation and then decreased slowly,and the individuals of the nematode that fed on Moniliaceae sp.(Ⅱ) were higher than those fed on M.corticolus (I) (P<0.01).In the first 12 days of incubation,the population of Moniliaceae sp.(Ⅱ) increased 2.5～3.5 times,while that of M.corticolus (Ⅰ) increased slower but caught up after the 12th day,and the density reached 5.0～5.7 times higher than the corresponding treatments with only fungi inoculation.The interactions encouraged the soil nitrogen mineralization of all four treatments,as compared with the control.Comparing the treatments with and without fungal-feeding nematode inoculation,the treatments with fungal-feeding nematode had a higher content of soil NH4+-N than those with only fungi inoculations,which indicated that nematode had a greater effect on soil nitrogen mineralization than fungi.As for the two species of fungi,M.corticolus (Ⅰ) had a greater effect on soil nitrogen mineralization than Moniliaceae sp.(Ⅱ).It was observed,however,that the nitrification rate declined as compared with the control.
    Effects of Bacillus thuringiensis transgenic rice and chemical insecticides on arthropod communities in paddy-fields
    LIU Zhicheng, YE Gongyin, HU Cui
    2004, (12):  2309-2314. 
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    This paper assessed the effects of cry1Ab/cry1Ac-carrying transgenic Bacillus thuringiensis rice (Bt rice) and chemical insecticides on the arthropod communities under paddy-field conditions in terms of arthropod guild dominance,family composition and dominance distribution of each guild,individuals of each guild,some common indices of arthropod communities,and community dissimilarity.In most cases,no significant differences were found between the Bt and control rice plots without any chemical insecticide spray in such arthropod community specific parameters as guild dominance,family composition and dominance distribution,temporal dynamics of the individuals of each guild or all arthropod,as well as some common community indices (including species richness,Shannon-Wiener diversity index,evenness index and dominant index) and their temporal dynamics.The similarity of arthropod community between the Bt and control rice plots were apparently higher.It was clear that Bt rice generally showed no marked negative effect on the arthropod community in paddy field.In contrast,some arthropod community specific parameters such as guild dominances in the control plot with chemical insecticide spray were in some cases markedly and even significantly different from those in the control plot without any chemical insecticide spray.The similarity of arthropod community between the control plots with and without chemical insecticide spray was relatively lower.It could be concluded that the effect of Bt rice on the arthropod community was apparently lower than that of chemical insecticides.
    Host transfer of Beauveria bassiana population in pine stand ecosystem and impact of its genetic diversity on sustainable control of Masson's pine caterpillars
    DING Degui, LI Zengzhi, FAN Meizhen, WANG Bin
    2004, (12):  2315-2320. 
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    In an anniversary investigation post inoculative release of Beauveria bassiana against Masson's pine caterpillars in a Masson's pine plantation,119 strains were isolated from 30 host insects,soil,litter and air.Based on an esterase isozyme analysis,all these strains were assigned to 32 esterase types,suggesting abundant genetic diversity.The esterase type 2 was assigned including 18 other strains from 11 different host insects,indicating that the released strain had successfully survived in different insect populations and persisted in enzootic condition in 12 insect populations including pine caterpillars and grey pine weevils.Other host insects could maintain the food chain when the target insect population was low.The other esterase types included 1～23 strains.The anniversary host transfer dynamics further revealed that B.bassiana could transfer among different host insects in the pine ecosystem.The virulence of the strains of each esterase differed substantially,which suggested that B.bassiana persisted and dispersed along more than one route,and each esterase stood for at least one branch in the food web.Some hosts connected different esterase types at nodal points,making the food web very complicated.In addition,the strains isolated from soil,litter,forest crown and air belonged to different esterase types,suggesting that a complex of saprophytic food chains existed in the plantation,which made the food web more complicated,and benefited the sustainable control of the Masson's pine caterpillar and other pest insects in the ecosystem.
    Effects of ultra low volume Beauveria bassiana oil formulation on biological diversity
    HUANG Jinshui, TANG Chensheng, XU Yaochang, WU Shoude, HE Xueyou, SHI Yuanjin
    2004, (12):  2321-2324. 
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    In 2001～2003,an ultra low volume (ULV) Beauveria bassiana (Bb) oil formulation was used to prevent against Dendrolimus punctatus,and its effect on biological diversity (species richness,individual number,species diversity index and evenness index,and dominant index) was investigated.The results showed that there were 473,392 and 266 species in non-control,Bb control and chemical control areas,respectively.The individual number ratio of natural enemies to pest in Bb control area (0.1049:1) was close to that in non-control area (0.1051:1),but much higher than that in chemical control area (0.0558:1).In Bb- and chemical control areas,the species richness and diversity decreased,but dominant index increased.There existed significant difference between chemical control and non-control areas,but no significant difference was found between Bb control and non-control areas.ULV Bb had no obvious effect on the natural enemies and non-target insects.
    Relationships between Aphis gossypii and its natural enemies in megranate field
    ZOU Yunding, LI Lei, BI Shoudong, LOU Zhi, DING Chengcheng, GAO Caiqiu, LI Changgen
    2004, (12):  2325-2329. 
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    In this paper,the relevancy of Aphis gossypii with its natural enemies was studied by using grey systematic analysis.The results showed that the major natural enemies of Aphis gossypii were Tetragnathidae (0.8607),Therdion octomaculatum (0.8058),Therdiono ctomaculatum (0.7989),Haramonia aiyridis (0.7881) and Chrysopa sepetempunctata (0.7758).As for the daily total predation,the natural enemies which highly associated with the ideal dominant natural enemies were Erigonidium graminicola (0.8975),Tromobidiidae (0.8132),Propylacea japonica (0.7806) and Chrysopa sepetempunctata (0.7669); while for the quantity,Erigonidium graminicola (0.8482),Chrysopa sinica (0.7533),Tetragnathidae (0.7532),Therdiono ctomaculatum (0.7411) and Chrysopa sepetempunctata (0.7716) were the major natural enemies.According to the relational grade of the individuals between various natural enemies and ideal dominant natural enemies,the major natural enemies were Erigonidium graminicola (0.8461),Tromobidiidae (0.7325),Propylacea japonica (0.6983),Chrysopa sepetempunctata (0.6815) and Chrysopa sinica (0.6757).The species having >0.9567 horizontal and vertical niche overlaps with Aphis gossyppii were Erigonidium graminicola,Chrysopa sepetempunctata and Tetragnathidae,while the temporal niche overlaps between Erigonidium graminicola,Chrysopa sepetempunctata,tetragnathidae and Aphis gossyppii were >0.4020.It could be concluded that the main natural enemies of Aphis gossyppii were Erigonidium graminicola,Chrysopa sepetempunctata and Tetragnathidae.
    Impact of automobile exhaust on membrane lipid peroxidation and protective enzyme activities in seedlings foliage of four northern broadleaved tree species
    MA Shuhua, WANG Qingcheng, LI Yacang
    2004, (12):  2330-2336. 
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    By means of fumigating one-year-old seedlings in open top chambers,this paper studied the impact of automobile exhaust on the pH value,relative conductivity,malondialdehyde (MDA) and chlorophyll contents,superoxide dismutase (SOD) and peroxidase (POD) activities,and ascorbic acid (ASA) content in the seedlings foliage of four tree species,Acer mono,Malus baccata,Prunus ussuriensis,and Acer ginnala.During the fumigation,the seedlings were exposed to the same exhaust gas concentration (25 μg·m-3,indicated by the NO2 concentration in exhaust) for different durations (1,3,5,7 d),and to different concentrations (40,60,80,100 μg NO2·m-3) for same duration (2 h).The results showed that the pH value and the chlorophyll and ascorbic acid (ASA) contents decreased,whereas the relative conductivity,malondialdehyde (MDA) content,and superoxide dismutase(SOD) and peroxidase(POD) activities increased with increasing fumigation duration and exhaust concentration.Obvious interspecies variations in term of physiological features were found.After treated 7 days with 25 μg NO2·m-3 and treated 2 h with 100 μg NO2·m-3,only a 1.5% and 2.7% decrease of cell juice pH was found in A.ginnala,respectively,compared to the control.The corresponding data for P.ussuriensis was 9.42% and 13.89%,followed by M.baccata.The chlorophyll content of A.mono,A.ginnala,M.baccata and P.ussuriensis was 83.0%,71.3%,68.7% and 54.9%,respectively of the control after 7 days treated with 25 μg NO2·m-3,and the corresponding data under 100 μg NO2·m-3 treatment was 60.2%,73.1%,43.4% and 51.2%,respectively.The decrease of ASA content and Acer ginnala was less in A.mono than in M.baccata and P.ussuriensis.The relative conductivity and MDA content of A.mono increased respectively by 68.1% and 52.5% in compared with control,while those of A.ginnala had the least increment.As for the 100 μg NO2·m-3 treatment,the maximum increases of relative conductivity (99.8%) and MDA content (52.5%) were found in M.baccata,while the least were found in A.mono and A.ginnala.The SOD and POD activities generally increased under the highest concentration of exhaust,with the exception of M.baccata.To summarize,almost all the test physiological features of A.ginnala were least affected,suggesting its great tolerance to exhaust stress,but in contrary,the greatest variation of the physiological features and the dramatic decline of SOD and POD activities of M.baccata at the highest exhaust concentration indicated that this tree species had the least tolerance to exhaust stress.
    Purification efficiency of several wetland macrophytes on COD and nitrogen removal from domestic sewage
    YUAN Donghai, REN Quanjin, GAO Shixiang, ZHANG Hong, YIN Daqiang, WANG Liansheng
    2004, (12):  2337-2341. 
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    In order to investigate the role of wetland macrophytes in waster water purification and to select appropriate native filter plants in constructed wetland,three vertical-flow constructed wetlands were built with river sands as the substrates of Acorus gramineus,Juncus effusus and Iris japonica,and one without plant as the control.Investigation on the removal of COD and total nitrogen (TN) from domestic sewage showed that within lower concentrations of COD (<200 mg稬-1) and TN (<30 mg稬-1),more than 90% of COD and 80% of TN were removed from domestic sewage in all constructed wetlands.When the concentration of COD and TN increased,the purification efficiency of all constructed wetlands decreased to some extent.The constructed wetlands with macrophytes had a higher efficiency than control.Among the three constructed wetlands with macrophytes,the one with Acorus gramineus had an average purification efficiency of 80.46% for COD and 77.77% for TN,that with Juncus effusus was 75.53% for COD and 71.17% for TN,and the one with Iris japonica was 70.50% for COD and 66.38% for TN.The constructed wetland without vegetation had an average purification efficiency of 61.39% for COD and 55.81% for TN.Acorus gramineus was more capable of removing COD and TN than Juncus effusus and Iris japonica.Vegetation biomass was the main factor affecting the removal rate of COD and nitrogen,because it significantly correlated with the ability of absorbing organic substance and nitrogen,and with the nitrification and denitrification around roots.
    Weed-suppressive effect of phenolic acids
    HE Huaqin, LIANG Yiyuan, JIA Xiaoli, SONG Biqing, GUO Yuchun, LIANG Kangjing, LIN Wenxiong
    2004, (12):  2342-2346. 
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    Allelochemical substitutions salicylic acid,p-hydroxybenzonic acid,cinnamic acid,vanillic acid and ferulic acid were tested in a gyrating regression experiment to study the weed-suppressive effect of phenolic acids on the root growth of barnyardgrass.The results showed that cinnamic acid had a significant inhibitory effect,its square item regression coefficient being -6.18; salicylic acid,p-hydroxybenzonic acid and ferulic acid had the same trend of weed-suppressive potential as cinnamic acid,while vanillic acid had a different weed-suppressive effect from the others.The inhibition rate (IR) on the root growth of barnyardgrass reached its highest level (78.5%) when 0.06 mmol稬-1 salicylic acid,0.60 mmol稬-1 p-hydrobenzonic acid,0.24 mmol稬-1 cinnamic acid,0.02 mmol稬-1 vannillic acid and 0.02 mmol稬-1 ferullic acid were mixed together to apply.
    Mitigation effect of several controlled-release N fertilizers on ammonia volatilization and related affecting factors
    SUN Kejun, MAO Xiaoyun, LU Qiming, JIA Aiping, LIAO Zongwen
    2004, (12):  2347-2350. 
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    By using static absorption and soil column leaching methods,this paper studied the behaviors of several controlled-release N fertilizers in soil under laboratory conditions.The results showed that under the application rate of 450 mg穔g-1,total ammonia volatilization from three controlled-release fertilizers decreased by 49.7%,28.0% and 71.2%,respectively,in comparing with common urea.When the application rate was 600 mg穔g-1,total ammonia volatilization decreased by 34.6%,12.3%,69.9%,respectively.Controlled-release fertilizers could markedly reduce total ammonia volatilization from soil and decrease environment pollution via fertilization.The results also indicated that total ammonia volatilization correlated significantly with soil urease activity,pH value and N leaching rate.The correlation coefficient between total ammonia volatilization and accumulated N leaching rate was 0.9533,and that between total ammonia volatilization and soil urease activity and pH value was 0.9533 and 0.9908,respectively.
    Heavy metals accumulation in different parts of Paeonia ostii and soils at copper tailings yard
    WANG Youbao, ZHANG Liqin, LIU Dengyi
    2004, (12):  2351-2354. 
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    The study on the heavy metals contamination of Paeonia ostii and soil at the copper tailings yard in Tongling City indicated that the soil of copper tailings yard was extremely barren,only with 1.1～3.4 g·kg-1 organic mater (1/15 of normal soil),but the contents of its Cu,Cd,Pb and Zn were much higher.Cu and Cd contents were 587.43～1 176.44 mg·kg-1 and 3.08～5.16 mg·kg-1,respectively,5～10 times higher than the grade two of national environmental quality standard for soils.Cu,Cd and Pb contents in Paeonia ostii exceeded the standard of medicine-use plants.Especially in its root peel,Cu and Cd contents stood at 31.50～64.00 mg·kg-1 and 0.98～1.45 mg·kg-1,respectively,1.6～3.6 times surpassing the standard,which meant that both Paeonia ostii and the soil had been severely polluted.There existed evident difference in the contents of heavy metals in different parts of Paeonia ostii.Stem,leaf and root peel had higher contents of Zn,Cd,Pb and Cu.The accumulation factors of Zn and Cd were higher than those of Cu and Pb,but they were all smaller in root peel.
    Cu and Pb contents in Dichondra repens leaf and their effects on its physiological indexes
    LI Jun, ZHOU Shoubiao, HUANG Wenjiang, WANG Guanglin
    2004, (12):  2355-2358. 
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    This paper analyzed the contents of Cu and Pb in Dichondra repens grown on Cu and Pb contaminated soil to determine if this plant is a hyperaccumulator of two elements.The results indicated that total content of Cu (44.8 g穔g-1) in the plant was higher than that of Pb (25.59 g穔g-1),and the contents of two elements were higher in roots and stems than in leaves and increased with increasing soil contamination.The accumulation coefficient of Cu (0.784) was higher than that of Pb (0.465).With the increasing concentrations of two heavy metals,the chlorophyll a content and chlorophyll a/b ratio in leaf decreased,the SOD activity increased to the peak and decreased subsequently,while the POD activity always maintained an increasing trend.The membrane permeability of cell was not significantly varied.
    Using paper as the carbon source for groundwater nitrate removal
    JIN Zanfang, CHEN Yingxu, OGURA Norio
    2004, (12):  2359-2363. 
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    The nitrate removal from groundwater was studied in laboratory columns packed with unprocessed paper as the sole substrate for microbial population.The results showed that the reactor with paper as carbon source started up fast,and temperature and hydraulic retention time (HRT) markedly affected the denitrification process.The denitrification rate at 25 ℃ was approximately 1.7 times higher than that at 14 ℃.When the initial concentration was 45.2 mg·L-1,99.6% of nitrate (nitrite was not detected) could be removed after 8.6 h at 25±1 ℃.The nitrogen removal rate was only 50% when HRT was 7.2 h.pH and dissolved oxygen (DO) had little effect on denitrification,and the nitrogen removal rate did not changed when pH value ranged between 6.0～9.0 and DO ranged between 0～6 mg·L-1.Biofilm was formed on the paper and consumed the paper during the whole process.Using the combined paper reactor and activated carbon adsorption at 25±1 ℃ and HRT 9.0 h,the nitrate could be completely removed if its initial concentration was not higher than 33.9 mgN·L-1 and the dissolved organic carbon (DOC) in the effluent was less than 11 mg·L-1.
    Ecosystem approach:A new concept for ecosystem management
    WANG Silong, ZHAO Shidong
    2004, (12):  2364-2368. 
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    Ecosystem approach (EA) was firstly proposed by ecologists in developed countries and then supported by a number of international institutions and NGOs,among which,CBD,IUCN and WWF played important roles.Ecosystem approach is an integrated strategy for the management of land,soil and bio-resources.The application of EA will help to reach a balance between conservation,sustainable use,and fair and equitable sharing of the benefits arising out of the utilization of biological resources.Ecosystem approach is a methodology of ecosystem management,focusing on the biological organisms and recognising that human beings,with their cultural diversity,are an integral component of many ecosystems.The decision V/6 adopted by the Conference of the Parties to the CBD at its fifth meeting in 2000 concretized the EA in the form of twelve principles and five operational guidelines.Our government has recently made a lot of efforts in ecosystem management at large scale with many important measures and obtained significant achievements,but the potential role of local governments,institutions and individuals has not been fully played.In the attempts of managing a specific ecosystem,there are many successful cases done by our ecologists,for example,the ecological management of Chinese fir plantation forest in central subtropical China.However,the whole ecosystem at national or regional level is confronted with a lot of serious problems,mainly because there is a lack of complete understanding of the significance of ecosystem management and a lack of guidelines or principles from an integrated scientific theory.The introduction and implementation of ecosystem approach will play an important role in improving the ecosystem management in China.
    Research advances in dynamic mechanism and its simulation of eco-hydrological process in forest catchment
    DIAO Yiwei, PEI Tiefan
    2004, (12):  2369-2376. 
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    Hydrological process is the key link between climatic fluctuations and ecologic dynamics of forests at spatial and temporal scales.To some extent,global climate change and large-scale human's activities will impact the spatial-temporal changes of eco-hydrological process in forest catchments in the future.Therefore,researches on the dynamic mechanism of eco-hydrological processes in forest catchments play a crucial role in understanding and controlling the rational use of ecological resources,resuming regional ecology,and sustainable development in economy.This paper described the interception,evapotranspiration and rainfall-runoff of forest ecological system and their effects on hydrological process.The spatial structure of soil moisture and its evolution with time were also the cause and consequence of forest.The spatial-temporal interaction between hydrologic and ecologic dynamics,the application of distributed hydrological model,and the eco-hydrological dynamics and cybernetics of forest would be the most exciting frontiers of the relative researches in the future.
    Organic agriculture and sustainable development
    LI Yu, WANG Gang
    2004, (12):  2377-2382. 
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    Basing on the research and practice of organic agriculture at home and abroad,this paper discussed the objectives of developing green food and the principles that must be persisted in the practice in China.In the light of the arguments concerning with sustainable agriculture,we also discussed the significance of “alternative agriculture" in theory and practice.Compared with conventional high-intensity agriculture,the production approaches of organic alternatives can improve soil fertility and have fewer detrimental effects on the environment.It is unclear whether conventional agriculture can be sustained because of the shortcomings presented in this paper,and it has taken scientists approximately one century to research and practice organic farming as a representative of alternative agriculture.The development of green food in China has only gone through more than ten years,and there would be some practical and theoretical effects on the development of China's green food if we exploit an environment-friendly production pattern of organic agriculture which majors in keeping human health and maintaining sustainable agriculture.
    Physiological and biochemical bases of xero-tolerance of fungal biocontrol agents and their application
    YE Sudan, FENG Mingguang
    2004, (12):  2383-2387. 
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    Hyphomycetes fungal biocontrol agents usually infect host insects by conidial germination and penetration into insect integument under high humidity condition which is generally the restrictive factor for the application of mycoinsecticides in insect control in the field.It is ideal to produce more xero-tolerant inocula (e.g.conidia) of the agents,although the current formulation technology has helped to some degree to reduce the dependence of fungal formulations on the high humidity.This paper reviewed the advance in basic and applied studies on the physiological and biochemical bases of fungal xero-tolerance and its water activity regulation in the past two decades.Possible approaches to make fungal formulations more xero-tolerant were discussed,with an emphasis on the increased accumulation of biologically compatible solutes such as low-molecular polyols and trehalose to the inocula produced for formulation.More efforts are necessitated to understand the mechanisms involved in molecular biology and in regulating the accumulation of the compatible solutes,and to explore for new technology to enhance the xero- tolerance of the fungal agents through biochemical regulation in mass production.
    Influence of elevated atmospheric CO2 on rhizosphere microbes and arbuscular mycorrhizae
    CHEN Jing, CHEN Xin, TANG Jianjun
    2004, (12):  2388-2392. 
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    The changes of microbial communities in rhizosphere and the formation of mycorrhizae play an important role in affecting the dynamics of plant communities and terrestrial ecosystems.This paper summarized and discussed the effects of elevated atmospheric CO2 on them.Under elevated atmospheric CO2,the carbohydrates accumulated in root systems increased,and the rhizospheric environment and its microbial communities as well as the formation of mycorrhizae changed.It is suggested that the researches in the future should be focused on the effects of rhizosphere microbes and arbuscular mycorrhizae on regulating the carbon dynamics of plant communities and terrestrial ecosystems under elevated atmospheric CO2.
    Comparison of clonal architecture between two divergent Leymus chinensis types in Songnen grassland
    HE Nianpeng, WU Ling, ZHOU Daowei
    2004, (12):  2393-2395. 
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    This paper studied the clonal architecture of two divergent Leymus chinensis types (grey-green type and yellow-green type) in Songnen grassland,and compared their internode length,spacer length,interbranching length,interbranching angle,and ramet population density and height under the same habitat.The results showed that there was no significant difference in these clonal characteristics except spacer length and ramet population density between the two types of L. chinensis,and yellow-green type,with less spacer length and more ramet density than grey-green type,should be more adaptable to the resourceful habitat.Moreover,the V-indices of the clonal architecture of two divergent L.chinensis types were all close to 1,and the difference was not significant.Therefore,both of the two types belonged to typical guerilla clonal plant.
    2004, 15(12):  2396-2400 . 
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    One year old Taxodium distichum seedlings were grown in pots with varied soil water and salt (NaC1) levels (alone and in combination) under greenhouse conditions to determine their effects on the growth and biomass allocation of the seedlings. The results showed that there were significant effects of soft salt and water contents on the relative height growth, relative stem diameter growth, biaomass increment and allocation, shoot/root ratio, seedling survival, ratio of branch to stem area, ratio of leaf mass to stem area, and ratio of leaf mass to branch area. According to the biomass increment, relative height growth and relative stem diameter growth, 20 treatments were classified into 3 groups by means of systematic cluster analysis. The first one was the treatments waterlogging, flooding, waterlogging + 0.15% NaC1, flooding + 0.15% NaC1, and waterlogging + 0.3% NaC1, which had a high growth, the second one was the treatments flooding + 0.45% NaC1, flooding + 0.3% NaCl, 75% of field capacity, and 75% of field capacity + 0.15% NaCl, which had a medium growth, and the last onewas the treatments 50% of field capacity, 50% of field capacity + 0.15% Nat1, waterlogging + 0.45% Nat1,25% of field capacity, 25% of field capacity + 0.15% NaC1, 75% of field capacity + 0.3% NaC1, 75% of field capacity + 0.45% NaC1, 25% of field capacity + 0.3% NaC1, 50% of field capacity + 0.3% NaC1, 50% of field capacity + 0.45% NaC1, and 25% of field capacity + 0.45% NaC1, which had a poor growth.
    Effects of soil salt and water contents on growth and biomass allocation of Taxodium distichum
    WANG Guibin, CAO Fuliang
    2004, (12):  2396-2400. 
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    One year old Taxodium distichum seedlings were grown in pots with varied soil water and salt(NaCl) levels (alone and in combination) under greenhouse conditions to determine their effects on the growth and biomass allocation of the seedlings.The results showed that there were significant effects of soil salt and water contents on the relative height growth,relative stem diameter growth,biaomass increment and allocation,shoot/root ratio,seedling survival,ratio of branch to stem area,ratio of leaf mass to stem area,and ratio of leaf mass to branch area.According to the biomass increment,relative height growth and relative stem diameter growth,20 treatments were classified into 3 groups by means of systematic cluster analysis.The first one was the treatments waterlogging,flooding,waterlogging + 0.15%NaCl,flooding+0.15%NaCl,and waterlogging + 0.3%NaCl,which had a high growth,the second one was the treatments flooding+0.45%NaCl,flooding+0.3%NaCl,75% of field capacity,and 75% of field capacity+ 0.15%NaCl,which had a medium growth,and the last one was the treatments 50% of field capacity,50% of field capacity+ 0.15%NaCl,waterlogging +0.45%NaCl,25% of field capacity,25% of field capacity+ 0.15%NaCl,75% of field capacity+ 0.3%NaCl,75% of field capacity+ 0.45%NaCl,25% of field capacity+ 0.3%NaCl,50% of field capacity+ 0.3%NaCl,50% of field capacity+ 0.45%NaCl,and 25% of field capacity+ 0.45%NaCl,which had a poor growth.
    Interspecific competition between Trichogramma confusum and T.pretiosum on Corcyra cephaloica factitious eggs
    HE Yurong, LÜ Lihua, CHEN Kewei
    2004, (12):  2401-2404. 
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    By means of single and mixed inoculation,this paper studied the interspecific competition between T.confusum and T.pretiosum on the factitious eggs of Corcyra cephaloica under different parasitoid densities,host densities and inoculated spaces.The results showed that for both singly and mixed inoculated groups,the parasitism increased with parasitoid density but decreased with host density,whereas the percentage of female progeny dropped with parasitoid density but enhanced with host density.No significant effect was observed on adult emergence for all parasitoid and host density treatments.In mixed inoculated group,the proportion of T.pretiosum in the progeny decreased with parasitoid density but increased with host density,and was more than 50% in all treatments,indicating that T.pretiosum had a stronger competitive ability than T.confusum.In the spaces ranging from 4 cm3 to 102 cm3,the parasitism decreased gradually in both singly and mixed inoculated groups.The percentage of female progeny and adult emergence had no significant difference among different inoculated spaces.In mixed inoculated group,the proportion of T.pretiosum in the progeny was more than 50% in all treatments except space 102 cm3,but decreased with space,which suggested that T.confusum could improve their competitive ability through increasing their search areas and looking for more hosts.
    Soil quality assessment of forest stand in different plantation esosystems
    HUANG Yu, WANG Silong, FENG Zongwei, GAO Iong, WANG Qingkui, HU Yalin, YAN Shaokui
    2004, (12):  2199-2205. 
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    After a clear-cutting of the first generation Cunninghamia lanceolata plantation in 1982,three plantation ecosystems,pure Michelia macclurei stand (PMS),pure Chinese-fir stand (PCS) and their mixed stand,were established in spring 1983,and their effects on soil characteristics were evaluated by measuring some soil physical,chemical,microbiological and biochemical parameters.After 20 years' plantation,all test indices showed differences among different forest management models.Both PMS and MCM had a favorable effect on soil fertility maintenance.Soil quality assessment showed that some soil functions,e.g.,water availability,nutrient availability,root suitability and soil quality index were all in a moderate level under the mixed and pure PMS stands,whereas in a relatively lower level under successive PCS stand.The results also showed that there existed close correlations between soil total organic C (TOC),cation exchange capacity (CEC),microbial biomass-C (Cmic) and other soil physical,chemical and biological indices.Therefore,TOC,CEC and Cmic could be used as the indicators in assessing soil quality in this study area.In addition,there were also positive correlations between soil microbial biomass-C and TOC,soil microbial biomass-N and total N,and soil microbial biomass-P and total P in the present study.
    Population structure and distribution pattern of rare plant communities in Houhe Nature Reserve
    DANG Haishan, JIANG Mingxi, TIAN Yuqiang, HUANG Handong, JIN Xia
    2004, (12):  2206-2210. 
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    An investigation on the size structure and spatial pattern of 26 major tree species with a diameter at breast height (DBH) ≥5 cm was made on a 1 hm2 fixed plot in the mixed evergreen and deciduous broad-leaved forest in Houhe National Nature Reserve of Central China.The results showed that 7 populations of the 26 species,i.e.,Dipteronia sinensi,Aesculus wilsonii,Pterostyrax psilophyllus,Davidia involucrate,Euptelea pleiosperma,Tetracentron sinense and Cercidiphyllum japonicum,were rare endangered species,and two of the 7 populations,T.sinense and C.japonicum,were very limited in numbers.The population structure of P.psilophyllus was in declining,and that of the rest was in growing.The spatial distribution pattern of P.psilophyllus,/i>A.wilsonii and T.sinense was in random,and that of the others was clumped.Among the other 19 non-rare populations,the population structure of P.wilsonii was in declining,that of D.lotus,A.palmatum,A.wilsonii,A.franchetii,M.cuneifolia and H.dulcis was stable,and the rest was in growing.The spatial distribution pattern of D.lotus and H.dulcis was in random,and that of the others was clumped.On the whole,the growing populations were dominant,amounting to 61.54%,and the stable and declining populations accounted for 6.92% and 11.54%,respectively.The results of the two judging methods were consistent,showing that the distribution pattern of clumping (80.77%) was dominant,while the random and even distribution patterns were infrequent.
    Biomass distribution patterns of Alnus hirsuta and Betula platyphylla-swamp ecotone communities in Changbai Mountains
    MU Changcheng, WAN Shucheng, SU Ping, SONG Hongwen, SUN Zhihu
    2004, (12):  2211-2216. 
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    In order to reveal the growth patterns of dominant tree species and the distribution patterns of community biomass along the horizontal environmental gradients or among the vertical layers of communities in Changbai Mountains,this paper studied the biomass distribution patterns of Alnus hirsuta-swamp and Betula platyphylla-swamp ecotone communities.The results showed that there were some differences in growth rate and in adaptability to habitats between A.hirsuta and B.platyphylla.In the wetland habitats of the ecotone,A.hirsuta grew 1～2 times faster than B.platyphylla,but along the gradient from swamp to forest,it grew slowly,while B.platyphylla grew fast.Therefore,A.hirsuta was a favorite tree species in wetland habitats.The distribution pattern of organ biomass was similar between A.hirsute and B.platyphylla,the trunk being 1/2,tree root 1/4,branch 1/10,bark 1.5/20,and leaf 1/20.The vertical distribution pattern of biomass was also similar between A.hirsute-swamp and B.platyphylla-swamp ecotone communities,the tree,shrub,and herbage layer accounted for 87%～90%,7%～9%,and 2%～3%,respectively in the whole ecotone communities.The community biomass increased linearly from swamp to forest with the change of environment factors.
    Position of Betula ermanii population ecotone in Changbai Mountains
    ZOU Chunjing, WANG Xiaochun, HAN Shijie
    2004, (12):  2217-2220. 
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    The vegetation on the northern slope of Changbai Mountains forms a vertical zone due to the vertical differentiation of moisture and heat conditions.Ecotones are obviously existed between different vegetation zones,but it is difficult to decide their positions.In the area from 1 400 m to 2 200 m elevation,we adopted the methods of gradient sampling,fractal analysis,population pattern analysis,and interspecific competition index analysis to describe Betula ermanii population ecotone.The results showed that there was a forest ecotone between Betula ermanii and Picea-Abies forest near elevation 1 650 m,and there was a forest line ecotone between Betula ermanii and alpine tundra near elevation 2 080 m.
    Major features of decline of Pinus sylvestris var.mongolica plantation on sandy land
    WU Xiangyun, JIANG Fengqi, LI Xiaodan, XUE Yang, QIU Sufen
    2004, (12):  2221-2224. 
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    In view of the decline of man-made sand-fixation forest of Pinus sylvestris var.mongolica in Zhanggutai sand land of Liaoning Province,this paper studied the major characteristics of the decline.The appearance of the declining man-made sand-fixation forest of Pinus sylvestris var.mongolica was grey green,its needle leaf was very thin,the blooming and fruiting rate was low,the average quantity of cones per tree was only 10.4～16.5,with only 6.96g to 7.39 g per thousand seeds,and there were many empty and astringent seeds.The seasonal dynamics of nutrients in 2-year-old pine needle leaf was similar,i.e.,the N and P contents decreased,while K content increased,showing that the nutrient cycle was imbalance.The chlorophyll content in 2-year-old needle leaf of declined forest was high,while that in 1-year-old healthy forest was also high but with a wide increasing range.The infected harm of shoot blight was the clearest mark to the decline of man-made sand-fixation forest of Pinus sylvestris var.mongolica.After the forest declined,the height and the DBH of the pine trees decreased evidently,and the structure of DBH distribution moved “left".The quantity of weak pine trees increased by 15.9%～27.2%,the roots decreased by 22.9%～28.9%,and the absorbing roots (diameter <0.5 cm) decreased most seriously.
    Decline regularity and causes of Pinus sylvestris var.mongolica plantation on sandy land
    WU Xiangyun, JIANG Fengqi, LI Xiaodan, XUE Yang, QIU Sufen
    2004, (12):  2225-2228. 
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    The study showed that the decline of Pinus sylvestris var.mongolica plantation out of its natural distribution area was a phenomenon of premature senility.The infected harm of shoot blight was the direct cause of Pinus sylvestris var.mongolica dying,but wasn't the basic reason.The decline of Pinus sylvestris var.mongolica was caused by the interaction of biological and other factors,which was "the third disease" beyond infectious and noninfectious diseases,namely,"decline disease of forest".Climate difference,improper management,unbalanced usage of soil water,and high content of N settled from air were the inducing factors,among which,climate difference and unbalanced usage of soil water were the main ones,while insect harm and shoot blight were the promoting factors.
    Effects of light and temperature on seed germination of Picea asperata and Betula albo-sinensis
    WU Yan, LIU Qing, HE Hai, LIN Bo, YIN Huajun
    2004, (12):  2229-2232. 
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    The effects of different light and temperature conditions on seed germination of two keystone species (Picea asperata and Betula albo-sinensis) in subalpine coniferous forests were studied by simulating environmental conditions in climatic chambers.The results indicated that the optimal temperature of seed germination for both species was 25 ℃,with the germination rate of 88.8±8.4% and 30.8±10.4%,respectively.Through multiple comparisons with Tukey's HSD,B.albo-sinensis was more sensitive to temperature than P.asperata.Seeds of P.asperata could germinate when the temperature reached 10 ℃,but those of B.albo-sinensis could not,which implied that the latter as a pioneer species of subalpine coniferous forest areas needed higher lowest temperature for seed germination.Day and night temperature difference (15 ℃/10 ℃,20 ℃/15 ℃ and 20 ℃/10 ℃) had significant effect on the germination rates of tested seeds,which was the highest under 20 ℃/15 ℃.A wide range of day and night temperature difference seemed to be unfavorable to the seed germination of B.albo-sinensis.Light intensity also had a marked effect on the germination rates of test seeds.Under 20% transmittance,the germination rate of P.asperata and B.albo-sinensis was the highest,being 83.0±6.6% and 29.2±5.5%,respectively,and the initiation time and regularity of germination were the best as well.Furthermore,B.albo-sinensis was less sensitive to light than P.asperata,which was determined by the life behavior of tree itself.
    Effects of 6-BA and AsA on photosynthesis photoinhibition of attached poplar leaves under osmotic stress of root
    FENG Yulong, MA Yongshuang, FENG Zhili
    2004, (12):  2233-2236. 
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    In order to know more about the relationships between photosynthesis photoinhibition and reactive oxygen species metabolism,the effects of 6-benzyladenine (6-BA) and ascorbate (AsA) on net photosynthetic rate (Pn),apparent quantum yield (AQY),superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities,O2-? generation rate,and H2O2 and malondialdehyde (MDA) contents were studied with attached leaves of poplar clone seedlings under osmotic stress of root.Under osmotic stress,the photosynthesis photoinhibition of attached poplar leaves,judged by the significant decrease of Pn and AQY,was aggravated,and the balance of reactive oxygen species metabolism was destroyed.The superoxide dismutase (SOD) activity increased,but ascorbate peroxidase (APX) activity decreased.In the meantime,the O2-? generation rate and the contents of H2O2 and malondialdehyde (MDA) increased.When osmotic stressed poplar seedlings were pretreated with 6-BA and AsA,the activities of SOD and APX increased,O2-? generation rate and H2O2 and MDA contents decreased,and photosynthesis photoinhibition was alleviated.The contents of reactive oxygen species and MDA in poplar leaves were negatively correlated with net photosynthetic rate and apparent quantum yield.It's indicated that the photosynthesis photoinhibition of attached leaves of poplar clone seedlings had intrinsic relations with the accumulation of reactive oxygen species under osmotic stress of root,and the alleviation effects of 6-BA and AsA on photosynthesis photoinhibition were related to their promotion effects to the scavenging system of reactive oxygen species.
    Effect of soil water potential on hydraulic parameters of Fraxinus mandshurica seedlings
    CUI Xiaoyang, SONG Jinfeng, QU Minghua
    2004, (12):  2237-2244. 
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    In this paper,soil water potential was controlled in the ranges of 0～-20 kPa(W1),-20～-40 kPa (W2), -40～-60 kPa (W3),-60～-80 kPa (W4) and -80～-160 kPa (W5) by a suite of specially designed root-sphere osmotic irrigation technique,and the dynamics of transpiration,water suction,tissue water potential and hydraulic resistance of Fraxinus mandshurica seedlings grown under these soil water conditions were studied.The results indicated that under sub-saturated soil water condition (W1),fine root water potential fluctuated at high levels from -0.08 MPa to -0.19MPa,which brought about the lowest soil-root hydraulic resistance (35.52 MPa·s-1·m-2·mol-1 in diurnal average),the highest water suction rate (4.44 mmol·m-2·s-1 in average from 10:00 to 14:00),and the strongest transpiration rate (5.11 mmol·m-2·s-1 in average from 10:00 to 14:00).Under field capacity (W2),soil-root hydraulic resistance increased several times above that under W1,water suction rate and transpiration rate declined significantly,while the diurnal single-peak pattern of transpiration was not altered.Under orderly increased soil water stress (W3～W5),soil-root hydraulic resistance (the average from 10:00 to 14:00) increased approximately 10～24 times above that under W1,which caused the consequent low water suction rate and low fluctuation levels of leaf water potential (-1.25 MPa～-1.94 MPa for W5),and transpiration was seriously restricted (the transpiration rate being only 0.91～1.55 mmol·m-2·s-1 at midday for W3～W5).It is concluded that soil water was not equally available to Fraxinus mandsharica seedlings in the test ranges of soil water potential,and significant water stress could occur when the soil water potential was lower than-40 kPa.
    Photosynthetic characteristics of main urban forest species Syringa oblata in Shenyang
    LI Haimei, HE Xingyuan, CHEN Wei
    2004, (12):  2245-2249. 
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    Using LI-6400 CO2 gas analysis system and by the methods of correlation analysis and multinomial regression, this paper studied the diurnal changes of Syringa oblata photosynthesis during different seasons and assessed the correlation between net photosynthetic rate and environmental factors. The results indicated that the photosynthetic rate showed a double-peak curve in spring and summer and a single peak curve in autumn. The major factors affecting the photosynthetic rate were the solar radiation and stomatal conductance in spring and summer, and the stomatal conductance and intercellular CO2 intensity in autumn. The related equation was also constructed in this paper.
    Dynamics of nutrient element iron in soil-plant ecosystem of the Songnen Plain Leymus chinensis grassland
    ZHOU Xiaomei, GUO Jixun, ZHAO Jiang
    2004, (12):  2250-2254. 
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    The study showed that in the soil-plant ecosystem of the Songnen Plain Leymus chinensis grassland,the contents of total and available iron in soil were relatively low,while Leymus chinensis was abundant in iron.The concentrations of soil total and available iron decreased with soil depth.Soil available iron positively correlated with soil organic matter,while negatively correlated with soil pH.The dynamics of soil total iron showed a “V" curve during the growth season,with the lowest in July,and that of soil available iron was similar to soil total iron from May to August,and gradually decreased after August.The iron concentration in Leymus chinensis changed dramatically with the trend of root>rhizome>leaf> litter >stem.The iron concentrations in leaf and stem had a fluctuant decrease,while those in root,rhizome and litter were fluctuated in “V" curve.Soil A layer enriched in a little more available iron.The iron activation with an average of 0.64% increased from May to August,and decreased after August,with the lowest in October.The shift ratio from underground to aboveground part of Leymus chinensis dropped during May-July,went up in August,and then dropped again.The average shift ratio from aboveground part to litter was 105.0%,which negatively correlated with that from underground to aboveground part.
    Changes of soil chemical properties in sheep urine patches in Inner Mongolia steppe
    LIU Zhongkuan, WANG Shiping, HAN Jianguo, WANG Yanfen, CHEN Zuozhong
    2004, (12):  2255-2260. 
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    Sheep play an important role in the nutrient cycling in extensively grazed grasslands,mainly through their annual return of around 5～25 kg N in the shape of urine.This return changes the temporal distribution of nutrients in soil and alters their bioavailability.Urine patches are the most important areas of the transformation and cycling of nutrients in the grazed grasslands.In order to make known the changes of soil chemical properties in sheep urine patches,an experiment was set up in the typical steppe area of central Inner Mongolia.The results indicated that soil pH value reached the maximum on the second day after urine excretion,and then declined.It maintained at around 6.5 from the 58th day,which was under the level of the control.Soil dissolved organic carbon (DOC) in urine patches exhibited the identical changing characteristics with soil pH,and had a significantly (P<0.01) positive correlation with it.Soil total dissolved phosphorus (TDP) increased significantly (P<0.05) after urine excretion,and reached the maximum at the 2nd day.The percentage of molybdate reactive phosphorus (MRP),dissolved organic phosphorus (DOP) and dissolved condensed phosphorus (DCP) showed significantly two changing phases,and there existed significantly (P<0.05) negative correlations between MRP,DOP and DCP.Soil NH4+-N reached the maximum on the 2nd day after urine excretion and then declined,while soil NO3--N increased significantly after 14 days and reached the maximum on the 21st day,showing significant “double peaks” characteristics.Soil dissolved organic nitrogen (DON) also increased significantly after urine excretion.
    Changes of four common plant populations growth and their anti-oxidative enzymatic system in desertification process
    ZHU Zhimei, YANG Chi
    2004, (12):  2261-2266. 
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    This paper studied the changes of the growth and anti-oxidative enzymatic system of four common plant populations during the desertification process of sandy grassland.The results showed that in the process of desertification,the individual height and density and the density percentage of the populations all had a decreasing trend.The growth of Melilotoides ruthenica was more vigorous before moderate desertification (MD) stage,but restricted after that.In MD stage,the growth of Leymus chinensis was heavily restricted,and its individual height,density and density percentage accounted for 57.19%,2.50% and 6.22% of those in original vegetation (OV) stage,respectively.The individual height and density of Cleistogenes squarrosa and Artemisia frigida increased in the stages of potential desertification (PD),light desertification (LD) or MD because of their phase status of dominant species and their stronger stress resistance.The SOD and POD activities of the common plant populations increased in PD and MD stages,but decreased in LD and heavy desertification (HD) stages.The CAT activity of Leymus chinensis was higher,whose response to desertification was not significant (P>0.05),and that of Melilotoides ruthenica increased significantly in PD and HD stages (P≤0.01).The activities of the three anti-oxidative enzymes in the common plant populations,except the CAT activity of Melilotoides ruthenica,decreased in HD stage.The MDA content in the common populations increased firstly,then decreased,and finally increased from OV to MD stage,and had a significant difference in different desertification gradients (P≤0.05).Based on the integrated analysis of the ecological and physiological changes,it could be concluded that Leymus chinensis was more sensitive to desertification,while Melilotoides ruthenica had a stronger bioenergy.
    Effects of grazing on architecture and small-scale pattern of grasses on artificial grassland in subtropical zone
    BAO Guozhang, KANG Chunli, GUO Ping
    2004, (12):  2267-2271. 
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    This study was conducted on a 5-year artificial grassland in subtropical zone of South China.The main types of established artificial grassland there were Dactylis glomerata-Lolium prenne-Trifolium repens and D.glomerata-T.repens pastures. Four grazing intensities were designed,i.e.,CK(no grazing),G1 (6 adult sheep·hm-2), G2(7.5 adult sheep·hm-2) and G3 (10 adult sheep·hm-2),and all the grazing plots were rotationally grazed. The architecture and small-scale pattern of grasses on the grazed and ungrazed grassland were discussed. After a period of 5-year grazing, the plant basal width and sward height of D. glomerata and T. pratense decreased gradually. In treatments CK,G1,G2 and G3,the basal width of D. glomerata was 6～8,2～4,0～2 and 0～2 cm, and that of T. pratense was 1～1.2, 6～8, 4～6 and 2～4 cm, respectively. The tuft density of D. glomerata in treatments CK, G1, G2 and G3 was 60, 95.1, 210.2 and 160 tufts·m-2, respectively. The tiller number per plant of D. glomerata decreased, while its tuft density increased significantly due to the increased grazing intensity. With the increase of grazing intensity, the internode length of T. repens decreased, while its branching angle increased. The average internode length in treatments CK, G1, G2 and G3 was 2.04, 1.69, 1.64 and 1.51 cm, while the branching angle was 46.5, 65, 73 and 77.3°, respectively. The average leaf density of T. repens in treatments CK, G1, G2 and G3 was 2.9, 13.0, 4.7 and 1.0·m-2, while the relevant stolon density was 19.9, 101, 142 and 82.6 m·m-2, respectively. Under moderate grazing intensity, both the leaf and stolon densities of T. repens increased. The main scale on small pattern of D. glomerata, T. repens and T. pratense was 2 cm×2 cm, which was further decreased under higher grazing intensity in the treatments of D. glomerata and T. pratense. Considering the heterogeneity of environmental resources, the change of the architecture and small-scale pattern could be regarded as an adaptation of grasses under grazing disturbance.
    Snow disaster in Aletai Region—Its remote sensing monitoring model and evaluation method
    LIANG Tiangang, GAO Xinhua, LIU Xingyuan
    2004, (12):  2272-2276. 
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    In this paper,a monitoring model of snow depth was built based on the 4 scenes of NOAA satellite digital images under sunshiny condition and the corresponding ground observation data from20 meteorological stations during 2 snow disasters from 1996 to 1997 in North Xinjiang.The pixel-based snow coverage rate and snow spatial classification were studied by using linear mixture spectrum disassembling method,and two grid data layers based quantified indices used for estimating snow hazard grade of grassland and animal husbandry were put forward.The results indicated that by using the snow monitoring model and linear mixture spectrum disassembling method,the image cell based snow depth and snow coverage rate could be calculated,and the precision of snow classification could be improved.The image cell based snow hazard index could systematically express the spatial distribution of snow,grass,animal and climate conditions,and reflect the snow hazard grade of grassland and animal husbandry.
    Relationships between biochemical qualities of paddy rice and climate conditions in the Anning River Valley
    PENG Guozhao, BAI Jian, WANG Jingbo
    2004, (12):  2277-2281. 
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    Base on the experimental data of paddy rice planted geographically periodically without control in the Anning River Valley of Sichuan Province,this paper quantitatively analyzed the effects of meteorological conditions from 40 days before heading to ripeness on the biochemical qualities of paddy rice,and developed a model about the integrated relationships between biochemical qualities of paddy rice and mean temperature,daily range of temperature and daylight hours,which would be of significance both for the instruction of paddy distribution in the Anning River Valley and for improving rice qualities via adjusting planting time.The results showed that climate conditions had a great effect on the biochemical qualities of paddy rice,which was different in ways and in critical periods.The period when the correlation between some ingredients of rice and climate conditions was most significant was before or after,or from before to after full heading,which widened the existing knowledge about the period which was important for paddy rice qualities forming.Applying this finding in the Anning River Valley during 2002～2003,the accumulated high-grade paddy farming area stood at 73 000 hm2,30 000 hm2 more than that in 2001,and brought 0.2 billion yuan increament to the peasants,promoting the development of high-grade paddy greatly.
    Effects of small amount precision seeding on winter wheat yield
    WU Dongbing, CAO Guangcai, LI Rongqi, ZHANG Zhongqi, QUAN Ming
    2004, (12):  2282-2286. 
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    A two-year autumn seeding experiment was conducted during 2001～2003 in Beijing to study the effects of small amount precision seeding on winter wheat yield.When the seeding amount was 22.5 kg·hm-2,the best average yield of winter wheat varieties DS No.1 and Linkang No.1 was 6 836.25 and 7 353.75 kg·hm-2,respectively,and some experimental plots had a yield surpassed 7 500 kg·hm-2.The test varieties had a normal expression of growth and development in their growth period,and the contents of total saccharide,proline and lysine in seedlings were higher,and the tillering ability of plant was stronger than the control.The net photosynthesis and transpiration rates,RS,COND and CINT of flag leaf showed the vigorous physiological functions of the plants,and the higher activities of nitrate reductase and SOD showed their stronger metabolism activity.There were more spikes per plant for the test varieties.In practicing small amount precision seeding,variety selection is the prerequisite,and sowing amount is the heart of the matter.
    Relationships between water-stable aggregates and nutrient status in black soil after reclamation
    YU Wantai, SHEN Shanmin, ZHANG Lu, MA Qiang, ZHAO Shaohua
    2004, (12):  2287-2291. 
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    The study on the dynamics of water-stable aggregates in black soil after reclamation and its relation to soil nutrient status showed that the contents of soil water-stable aggregates decreased significantly at initial reclamation stage,but the declining became small with time. >0.25 mm water-stable aggregates had a significant correlation with soil organic C,total N,total P and CEC,the correlation coefficients being 0.7625,0.6794,0.6084 and 0.8134,respectively,and also had a significant correlation with soil exchangeable Ca,Mg,K and Na.A closer relationship of the aggregates was found with soil organic C and CEC than with other fertility properties,while no evident correlation was existed between the aggregates and soil total K,available P,available K and slow-release K.In order to maintain a good aggregate structure of black soil,it is of most importance to concern a proper balance of soil organic C.
    Effects of land use and vegetation restoration on soil quality in a small catchment of the Loess Plateau
    GONG Jie, CHEN Liding, FU Bojie, LI Yanmei, HUANG Zhilin, HUANG Yilong, PENG Hongjia
    2004, (12):  2292-2296. 
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    Soil quality improvement plays an important role in sustaining global biosphere.This paper studied the changes of soil quality after 25 years' land use and vegetation restoration at the Anjiapo catchment of western Loess Plateau.The analyses of soil characteristics of wasteland,almond land,farmland,pineland,shrub land and fallow land showed that different land use and vegetation restoration had different effects on soil integrated fertility index.Soil organic matter content was increased due to planting shrubs and forests.Both vegetation restoration and fallow could improve soil quality.Cultivation practice could decrease soil nutrient levels,and cropland soil was degraded.Shrub soil formed “fertile island” in the semi-arid region.Fallow could improve soil fertility to some extent.Human activities and vegetation restoration could affect soil nutrient contents after land use pattern was changed.With the launch out into the “Grand development of Western China”,“Grain for Green Project” and ecological restoration,both shrub planting and fallow(natural restoration)should be the optional choices to restore soil fertility,as they could decrease soil erosion and improve soil condition at catchment scale,especially in the hilly and gully loess area.Integrative control of small catchment may be the best way for the sustainable development of the semi-arid hilly area of Loess Plateau.
    Dynamic analysis of land use and land coverage in mid-eastern China during 1988～2000
    TIAN Ziqiang, ZHENG Binghui, WANG Wenjie, LI Zicheng
    2004, (12):  2297-2303. 
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    Using remote sensing(RS) and geographic information system(GIS) technologies and based on the documentary and field sampling data,this paper constructed and analyzed the 1988 and 2000 landscape maps of mid-eastern China.The mapping area of mid-eastern China was about 2.87?106km2.With the rapid increase of economy and population,the area of farmland and town in mid-eastern China increased 10.921?105hm2 and 13.754?105 hm2,accounted for a 2.14% and 19.25% increase,respectively from 1988 to 2000.At the same time,the forest area decreased 17.83?104hm2,declined by 1.12%,because of the increasing demand for lumber provision and reclamation.The meadow area in 2000 increased 19.287?105 hm2,ascending 7.75%,while the coverage and quality of grassland declined,owing to the deteriorating environment.The untilled land in 2000 dropped 34.31%,contrast with 1988 by the reason of a large number of lands being exploited.
    Interactions between fungal-feeding nematodes and fungi and their effects on soil nitrogen mineralization
    LI Huixin, MAO Xiaofang, HU Feng, MA Jiping
    2004, (12):  2304-2308. 
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    A species of fungal-feeding nematodes (Aphelenchus avenae) and two species of fungi (Micheli corticolus and Moniliaceae sp.) were isolated from an alluvial soil planted with paddy-rice and wheat in subtropical region.In order to approach their interactions and effects on soil nitrogen mineralization,a gnotobiotic microcosm experiment was carried out with four treatments,i.e.,1) soil + fungi-I (M.corticolus),2) soil + fungi Ⅰ + Aphelenchus avenae,3) soil + fungi II (Moniliaceae sp.),and 4) soil + fungi Ⅱ + Aphelenchus avenae at 22 ℃ for 25 days.The results showed that the individuals of nematode and fungi were increased simultaneously,suggesting that the inoculation of A.avenae stimulated the growth of fungi.The fungal-feeding nematode increased during the initial 20 days of incubation and then decreased slowly,and the individuals of the nematode that fed on Moniliaceae sp.(Ⅱ) were higher than those fed on M.corticolus (I) (P<0.01).In the first 12 days of incubation,the population of Moniliaceae sp.(Ⅱ) increased 2.5～3.5 times,while that of M.corticolus (Ⅰ) increased slower but caught up after the 12th day,and the density reached 5.0～5.7 times higher than the corresponding treatments with only fungi inoculation.The interactions encouraged the soil nitrogen mineralization of all four treatments,as compared with the control.Comparing the treatments with and without fungal-feeding nematode inoculation,the treatments with fungal-feeding nematode had a higher content of soil NH4+-N than those with only fungi inoculations,which indicated that nematode had a greater effect on soil nitrogen mineralization than fungi.As for the two species of fungi,M.corticolus (Ⅰ) had a greater effect on soil nitrogen mineralization than Moniliaceae sp.(Ⅱ).It was observed,however,that the nitrification rate declined as compared with the control.
    Effects of Bacillus thuringiensis transgenic rice and chemical insecticides on arthropod communities in paddy-fields
    LIU Zhicheng, YE Gongyin, HU Cui
    2004, (12):  2309-2314. 
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    This paper assessed the effects of cry1Ab/cry1Ac-carrying transgenic Bacillus thuringiensis rice (Bt rice) and chemical insecticides on the arthropod communities under paddy-field conditions in terms of arthropod guild dominance,family composition and dominance distribution of each guild,individuals of each guild,some common indices of arthropod communities,and community dissimilarity.In most cases,no significant differences were found between the Bt and control rice plots without any chemical insecticide spray in such arthropod community specific parameters as guild dominance,family composition and dominance distribution,temporal dynamics of the individuals of each guild or all arthropod,as well as some common community indices (including species richness,Shannon-Wiener diversity index,evenness index and dominant index) and their temporal dynamics.The similarity of arthropod community between the Bt and control rice plots were apparently higher.It was clear that Bt rice generally showed no marked negative effect on the arthropod community in paddy field.In contrast,some arthropod community specific parameters such as guild dominances in the control plot with chemical insecticide spray were in some cases markedly and even significantly different from those in the control plot without any chemical insecticide spray.The similarity of arthropod community between the control plots with and without chemical insecticide spray was relatively lower.It could be concluded that the effect of Bt rice on the arthropod community was apparently lower than that of chemical insecticides.
    Host transfer of Beauveria bassiana population in pine stand ecosystem and impact of its genetic diversity on sustainable control of Masson's pine caterpillars
    DING Degui, LI Zengzhi, FAN Meizhen, WANG Bin
    2004, (12):  2315-2320. 
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    In an anniversary investigation post inoculative release of Beauveria bassiana against Masson's pine caterpillars in a Masson's pine plantation,119 strains were isolated from 30 host insects,soil,litter and air.Based on an esterase isozyme analysis,all these strains were assigned to 32 esterase types,suggesting abundant genetic diversity.The esterase type 2 was assigned including 18 other strains from 11 different host insects,indicating that the released strain had successfully survived in different insect populations and persisted in enzootic condition in 12 insect populations including pine caterpillars and grey pine weevils.Other host insects could maintain the food chain when the target insect population was low.The other esterase types included 1～23 strains.The anniversary host transfer dynamics further revealed that B.bassiana could transfer among different host insects in the pine ecosystem.The virulence of the strains of each esterase differed substantially,which suggested that B.bassiana persisted and dispersed along more than one route,and each esterase stood for at least one branch in the food web.Some hosts connected different esterase types at nodal points,making the food web very complicated.In addition,the strains isolated from soil,litter,forest crown and air belonged to different esterase types,suggesting that a complex of saprophytic food chains existed in the plantation,which made the food web more complicated,and benefited the sustainable control of the Masson's pine caterpillar and other pest insects in the ecosystem.
    Effects of ultra low volume Beauveria bassiana oil formulation on biological diversity
    HUANG Jinshui, TANG Chensheng, XU Yaochang, WU Shoude, HE Xueyou, SHI Yuanjin
    2004, (12):  2321-2324. 
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    In 2001～2003,an ultra low volume (ULV) Beauveria bassiana (Bb) oil formulation was used to prevent against Dendrolimus punctatus,and its effect on biological diversity (species richness,individual number,species diversity index and evenness index,and dominant index) was investigated.The results showed that there were 473,392 and 266 species in non-control,Bb control and chemical control areas,respectively.The individual number ratio of natural enemies to pest in Bb control area (0.1049:1) was close to that in non-control area (0.1051:1),but much higher than that in chemical control area (0.0558:1).In Bb- and chemical control areas,the species richness and diversity decreased,but dominant index increased.There existed significant difference between chemical control and non-control areas,but no significant difference was found between Bb control and non-control areas.ULV Bb had no obvious effect on the natural enemies and non-target insects.
    Relationships between Aphis gossypii and its natural enemies in megranate field
    ZOU Yunding, LI Lei, BI Shoudong, LOU Zhi, DING Chengcheng, GAO Caiqiu, LI Changgen
    2004, (12):  2325-2329. 
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    In this paper,the relevancy of Aphis gossypii with its natural enemies was studied by using grey systematic analysis.The results showed that the major natural enemies of Aphis gossypii were Tetragnathidae (0.8607),Therdion octomaculatum (0.8058),Therdiono ctomaculatum (0.7989),Haramonia aiyridis (0.7881) and Chrysopa sepetempunctata (0.7758).As for the daily total predation,the natural enemies which highly associated with the ideal dominant natural enemies were Erigonidium graminicola (0.8975),Tromobidiidae (0.8132),Propylacea japonica (0.7806) and Chrysopa sepetempunctata (0.7669); while for the quantity,Erigonidium graminicola (0.8482),Chrysopa sinica (0.7533),Tetragnathidae (0.7532),Therdiono ctomaculatum (0.7411) and Chrysopa sepetempunctata (0.7716) were the major natural enemies.According to the relational grade of the individuals between various natural enemies and ideal dominant natural enemies,the major natural enemies were Erigonidium graminicola (0.8461),Tromobidiidae (0.7325),Propylacea japonica (0.6983),Chrysopa sepetempunctata (0.6815) and Chrysopa sinica (0.6757).The species having >0.9567 horizontal and vertical niche overlaps with Aphis gossyppii were Erigonidium graminicola,Chrysopa sepetempunctata and Tetragnathidae,while the temporal niche overlaps between Erigonidium graminicola,Chrysopa sepetempunctata,tetragnathidae and Aphis gossyppii were >0.4020.It could be concluded that the main natural enemies of Aphis gossyppii were Erigonidium graminicola,Chrysopa sepetempunctata and Tetragnathidae.
    Impact of automobile exhaust on membrane lipid peroxidation and protective enzyme activities in seedlings foliage of four northern broadleaved tree species
    MA Shuhua, WANG Qingcheng, LI Yacang
    2004, (12):  2330-2336. 
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    By means of fumigating one-year-old seedlings in open top chambers,this paper studied the impact of automobile exhaust on the pH value,relative conductivity,malondialdehyde (MDA) and chlorophyll contents,superoxide dismutase (SOD) and peroxidase (POD) activities,and ascorbic acid (ASA) content in the seedlings foliage of four tree species,Acer mono,Malus baccata,Prunus ussuriensis,and Acer ginnala.During the fumigation,the seedlings were exposed to the same exhaust gas concentration (25 μg·m-3,indicated by the NO2 concentration in exhaust) for different durations (1,3,5,7 d),and to different concentrations (40,60,80,100 μg NO2·m-3) for same duration (2 h).The results showed that the pH value and the chlorophyll and ascorbic acid (ASA) contents decreased,whereas the relative conductivity,malondialdehyde (MDA) content,and superoxide dismutase(SOD) and peroxidase(POD) activities increased with increasing fumigation duration and exhaust concentration.Obvious interspecies variations in term of physiological features were found.After treated 7 days with 25 μg NO2·m-3 and treated 2 h with 100 μg NO2·m-3,only a 1.5% and 2.7% decrease of cell juice pH was found in A.ginnala,respectively,compared to the control.The corresponding data for P.ussuriensis was 9.42% and 13.89%,followed by M.baccata.The chlorophyll content of A.mono,A.ginnala,M.baccata and P.ussuriensis was 83.0%,71.3%,68.7% and 54.9%,respectively of the control after 7 days treated with 25 μg NO2·m-3,and the corresponding data under 100 μg NO2·m-3 treatment was 60.2%,73.1%,43.4% and 51.2%,respectively.The decrease of ASA content and Acer ginnala was less in A.mono than in M.baccata and P.ussuriensis.The relative conductivity and MDA content of A.mono increased respectively by 68.1% and 52.5% in compared with control,while those of A.ginnala had the least increment.As for the 100 μg NO2·m-3 treatment,the maximum increases of relative conductivity (99.8%) and MDA content (52.5%) were found in M.baccata,while the least were found in A.mono and A.ginnala.The SOD and POD activities generally increased under the highest concentration of exhaust,with the exception of M.baccata.To summarize,almost all the test physiological features of A.ginnala were least affected,suggesting its great tolerance to exhaust stress,but in contrary,the greatest variation of the physiological features and the dramatic decline of SOD and POD activities of M.baccata at the highest exhaust concentration indicated that this tree species had the least tolerance to exhaust stress.
    Purification efficiency of several wetland macrophytes on COD and nitrogen removal from domestic sewage
    YUAN Donghai, REN Quanjin, GAO Shixiang, ZHANG Hong, YIN Daqiang, WANG Liansheng
    2004, (12):  2337-2341. 
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    In order to investigate the role of wetland macrophytes in waster water purification and to select appropriate native filter plants in constructed wetland,three vertical-flow constructed wetlands were built with river sands as the substrates of Acorus gramineus,Juncus effusus and Iris japonica,and one without plant as the control.Investigation on the removal of COD and total nitrogen (TN) from domestic sewage showed that within lower concentrations of COD (<200 mg稬-1) and TN (<30 mg稬-1),more than 90% of COD and 80% of TN were removed from domestic sewage in all constructed wetlands.When the concentration of COD and TN increased,the purification efficiency of all constructed wetlands decreased to some extent.The constructed wetlands with macrophytes had a higher efficiency than control.Among the three constructed wetlands with macrophytes,the one with Acorus gramineus had an average purification efficiency of 80.46% for COD and 77.77% for TN,that with Juncus effusus was 75.53% for COD and 71.17% for TN,and the one with Iris japonica was 70.50% for COD and 66.38% for TN.The constructed wetland without vegetation had an average purification efficiency of 61.39% for COD and 55.81% for TN.Acorus gramineus was more capable of removing COD and TN than Juncus effusus and Iris japonica.Vegetation biomass was the main factor affecting the removal rate of COD and nitrogen,because it significantly correlated with the ability of absorbing organic substance and nitrogen,and with the nitrification and denitrification around roots.
    Weed-suppressive effect of phenolic acids
    HE Huaqin, LIANG Yiyuan, JIA Xiaoli, SONG Biqing, GUO Yuchun, LIANG Kangjing, LIN Wenxiong
    2004, (12):  2342-2346. 
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    Allelochemical substitutions salicylic acid,p-hydroxybenzonic acid,cinnamic acid,vanillic acid and ferulic acid were tested in a gyrating regression experiment to study the weed-suppressive effect of phenolic acids on the root growth of barnyardgrass.The results showed that cinnamic acid had a significant inhibitory effect,its square item regression coefficient being -6.18; salicylic acid,p-hydroxybenzonic acid and ferulic acid had the same trend of weed-suppressive potential as cinnamic acid,while vanillic acid had a different weed-suppressive effect from the others.The inhibition rate (IR) on the root growth of barnyardgrass reached its highest level (78.5%) when 0.06 mmol稬-1 salicylic acid,0.60 mmol稬-1 p-hydrobenzonic acid,0.24 mmol稬-1 cinnamic acid,0.02 mmol稬-1 vannillic acid and 0.02 mmol稬-1 ferullic acid were mixed together to apply.
    Mitigation effect of several controlled-release N fertilizers on ammonia volatilization and related affecting factors
    SUN Kejun, MAO Xiaoyun, LU Qiming, JIA Aiping, LIAO Zongwen
    2004, (12):  2347-2350. 
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    By using static absorption and soil column leaching methods,this paper studied the behaviors of several controlled-release N fertilizers in soil under laboratory conditions.The results showed that under the application rate of 450 mg穔g-1,total ammonia volatilization from three controlled-release fertilizers decreased by 49.7%,28.0% and 71.2%,respectively,in comparing with common urea.When the application rate was 600 mg穔g-1,total ammonia volatilization decreased by 34.6%,12.3%,69.9%,respectively.Controlled-release fertilizers could markedly reduce total ammonia volatilization from soil and decrease environment pollution via fertilization.The results also indicated that total ammonia volatilization correlated significantly with soil urease activity,pH value and N leaching rate.The correlation coefficient between total ammonia volatilization and accumulated N leaching rate was 0.9533,and that between total ammonia volatilization and soil urease activity and pH value was 0.9533 and 0.9908,respectively.
    Heavy metals accumulation in different parts of Paeonia ostii and soils at copper tailings yard
    WANG Youbao, ZHANG Liqin, LIU Dengyi
    2004, (12):  2351-2354. 
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    The study on the heavy metals contamination of Paeonia ostii and soil at the copper tailings yard in Tongling City indicated that the soil of copper tailings yard was extremely barren,only with 1.1～3.4 g·kg-1 organic mater (1/15 of normal soil),but the contents of its Cu,Cd,Pb and Zn were much higher.Cu and Cd contents were 587.43～1 176.44 mg·kg-1 and 3.08～5.16 mg·kg-1,respectively,5～10 times higher than the grade two of national environmental quality standard for soils.Cu,Cd and Pb contents in Paeonia ostii exceeded the standard of medicine-use plants.Especially in its root peel,Cu and Cd contents stood at 31.50～64.00 mg·kg-1 and 0.98～1.45 mg·kg-1,respectively,1.6～3.6 times surpassing the standard,which meant that both Paeonia ostii and the soil had been severely polluted.There existed evident difference in the contents of heavy metals in different parts of Paeonia ostii.Stem,leaf and root peel had higher contents of Zn,Cd,Pb and Cu.The accumulation factors of Zn and Cd were higher than those of Cu and Pb,but they were all smaller in root peel.
    Cu and Pb contents in Dichondra repens leaf and their effects on its physiological indexes
    LI Jun, ZHOU Shoubiao, HUANG Wenjiang, WANG Guanglin
    2004, (12):  2355-2358. 
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    This paper analyzed the contents of Cu and Pb in Dichondra repens grown on Cu and Pb contaminated soil to determine if this plant is a hyperaccumulator of two elements.The results indicated that total content of Cu (44.8 g穔g-1) in the plant was higher than that of Pb (25.59 g穔g-1),and the contents of two elements were higher in roots and stems than in leaves and increased with increasing soil contamination.The accumulation coefficient of Cu (0.784) was higher than that of Pb (0.465).With the increasing concentrations of two heavy metals,the chlorophyll a content and chlorophyll a/b ratio in leaf decreased,the SOD activity increased to the peak and decreased subsequently,while the POD activity always maintained an increasing trend.The membrane permeability of cell was not significantly varied.
    Using paper as the carbon source for groundwater nitrate removal
    JIN Zanfang, CHEN Yingxu, OGURA Norio
    2004, (12):  2359-2363. 
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    The nitrate removal from groundwater was studied in laboratory columns packed with unprocessed paper as the sole substrate for microbial population.The results showed that the reactor with paper as carbon source started up fast,and temperature and hydraulic retention time (HRT) markedly affected the denitrification process.The denitrification rate at 25 ℃ was approximately 1.7 times higher than that at 14 ℃.When the initial concentration was 45.2 mg·L-1,99.6% of nitrate (nitrite was not detected) could be removed after 8.6 h at 25±1 ℃.The nitrogen removal rate was only 50% when HRT was 7.2 h.pH and dissolved oxygen (DO) had little effect on denitrification,and the nitrogen removal rate did not changed when pH value ranged between 6.0～9.0 and DO ranged between 0～6 mg·L-1.Biofilm was formed on the paper and consumed the paper during the whole process.Using the combined paper reactor and activated carbon adsorption at 25±1 ℃ and HRT 9.0 h,the nitrate could be completely removed if its initial concentration was not higher than 33.9 mgN·L-1 and the dissolved organic carbon (DOC) in the effluent was less than 11 mg·L-1.
    Ecosystem approach:A new concept for ecosystem management
    WANG Silong, ZHAO Shidong
    2004, (12):  2364-2368. 
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    Ecosystem approach (EA) was firstly proposed by ecologists in developed countries and then supported by a number of international institutions and NGOs,among which,CBD,IUCN and WWF played important roles.Ecosystem approach is an integrated strategy for the management of land,soil and bio-resources.The application of EA will help to reach a balance between conservation,sustainable use,and fair and equitable sharing of the benefits arising out of the utilization of biological resources.Ecosystem approach is a methodology of ecosystem management,focusing on the biological organisms and recognising that human beings,with their cultural diversity,are an integral component of many ecosystems.The decision V/6 adopted by the Conference of the Parties to the CBD at its fifth meeting in 2000 concretized the EA in the form of twelve principles and five operational guidelines.Our government has recently made a lot of efforts in ecosystem management at large scale with many important measures and obtained significant achievements,but the potential role of local governments,institutions and individuals has not been fully played.In the attempts of managing a specific ecosystem,there are many successful cases done by our ecologists,for example,the ecological management of Chinese fir plantation forest in central subtropical China.However,the whole ecosystem at national or regional level is confronted with a lot of serious problems,mainly because there is a lack of complete understanding of the significance of ecosystem management and a lack of guidelines or principles from an integrated scientific theory.The introduction and implementation of ecosystem approach will play an important role in improving the ecosystem management in China.
    Research advances in dynamic mechanism and its simulation of eco-hydrological process in forest catchment
    DIAO Yiwei, PEI Tiefan
    2004, (12):  2369-2376. 
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    Hydrological process is the key link between climatic fluctuations and ecologic dynamics of forests at spatial and temporal scales.To some extent,global climate change and large-scale human's activities will impact the spatial-temporal changes of eco-hydrological process in forest catchments in the future.Therefore,researches on the dynamic mechanism of eco-hydrological processes in forest catchments play a crucial role in understanding and controlling the rational use of ecological resources,resuming regional ecology,and sustainable development in economy.This paper described the interception,evapotranspiration and rainfall-runoff of forest ecological system and their effects on hydrological process.The spatial structure of soil moisture and its evolution with time were also the cause and consequence of forest.The spatial-temporal interaction between hydrologic and ecologic dynamics,the application of distributed hydrological model,and the eco-hydrological dynamics and cybernetics of forest would be the most exciting frontiers of the relative researches in the future.
    Organic agriculture and sustainable development
    LI Yu, WANG Gang
    2004, (12):  2377-2382. 
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    Basing on the research and practice of organic agriculture at home and abroad,this paper discussed the objectives of developing green food and the principles that must be persisted in the practice in China.In the light of the arguments concerning with sustainable agriculture,we also discussed the significance of “alternative agriculture" in theory and practice.Compared with conventional high-intensity agriculture,the production approaches of organic alternatives can improve soil fertility and have fewer detrimental effects on the environment.It is unclear whether conventional agriculture can be sustained because of the shortcomings presented in this paper,and it has taken scientists approximately one century to research and practice organic farming as a representative of alternative agriculture.The development of green food in China has only gone through more than ten years,and there would be some practical and theoretical effects on the development of China's green food if we exploit an environment-friendly production pattern of organic agriculture which majors in keeping human health and maintaining sustainable agriculture.
    Physiological and biochemical bases of xero-tolerance of fungal biocontrol agents and their application
    YE Sudan, FENG Mingguang
    2004, (12):  2383-2387. 
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    Hyphomycetes fungal biocontrol agents usually infect host insects by conidial germination and penetration into insect integument under high humidity condition which is generally the restrictive factor for the application of mycoinsecticides in insect control in the field.It is ideal to produce more xero-tolerant inocula (e.g.conidia) of the agents,although the current formulation technology has helped to some degree to reduce the dependence of fungal formulations on the high humidity.This paper reviewed the advance in basic and applied studies on the physiological and biochemical bases of fungal xero-tolerance and its water activity regulation in the past two decades.Possible approaches to make fungal formulations more xero-tolerant were discussed,with an emphasis on the increased accumulation of biologically compatible solutes such as low-molecular polyols and trehalose to the inocula produced for formulation.More efforts are necessitated to understand the mechanisms involved in molecular biology and in regulating the accumulation of the compatible solutes,and to explore for new technology to enhance the xero- tolerance of the fungal agents through biochemical regulation in mass production.
    Influence of elevated atmospheric CO2 on rhizosphere microbes and arbuscular mycorrhizae
    CHEN Jing, CHEN Xin, TANG Jianjun
    2004, (12):  2388-2392. 
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    The changes of microbial communities in rhizosphere and the formation of mycorrhizae play an important role in affecting the dynamics of plant communities and terrestrial ecosystems.This paper summarized and discussed the effects of elevated atmospheric CO2 on them.Under elevated atmospheric CO2,the carbohydrates accumulated in root systems increased,and the rhizospheric environment and its microbial communities as well as the formation of mycorrhizae changed.It is suggested that the researches in the future should be focused on the effects of rhizosphere microbes and arbuscular mycorrhizae on regulating the carbon dynamics of plant communities and terrestrial ecosystems under elevated atmospheric CO2.
    Comparison of clonal architecture between two divergent Leymus chinensis types in Songnen grassland
    HE Nianpeng, WU Ling, ZHOU Daowei
    2004, (12):  2393-2395. 
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    This paper studied the clonal architecture of two divergent Leymus chinensis types (grey-green type and yellow-green type) in Songnen grassland,and compared their internode length,spacer length,interbranching length,interbranching angle,and ramet population density and height under the same habitat.The results showed that there was no significant difference in these clonal characteristics except spacer length and ramet population density between the two types of L. chinensis,and yellow-green type,with less spacer length and more ramet density than grey-green type,should be more adaptable to the resourceful habitat.Moreover,the V-indices of the clonal architecture of two divergent L.chinensis types were all close to 1,and the difference was not significant.Therefore,both of the two types belonged to typical guerilla clonal plant.
    Effects of soil salt and water contents on growth and biomass allocation of Taxodium distichum
    WANG Guibin, CAO Fuliang
    2004, (12):  2396-2400. 
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    One year old Taxodium distichum seedlings were grown in pots with varied soil water and salt(NaCl) levels (alone and in combination) under greenhouse conditions to determine their effects on the growth and biomass allocation of the seedlings.The results showed that there were significant effects of soil salt and water contents on the relative height growth,relative stem diameter growth,biaomass increment and allocation,shoot/root ratio,seedling survival,ratio of branch to stem area,ratio of leaf mass to stem area,and ratio of leaf mass to branch area.According to the biomass increment,relative height growth and relative stem diameter growth,20 treatments were classified into 3 groups by means of systematic cluster analysis.The first one was the treatments waterlogging,flooding,waterlogging + 0.15%NaCl,flooding+0.15%NaCl,and waterlogging + 0.3%NaCl,which had a high growth,the second one was the treatments flooding+0.45%NaCl,flooding+0.3%NaCl,75% of field capacity,and 75% of field capacity+ 0.15%NaCl,which had a medium growth,and the last one was the treatments 50% of field capacity,50% of field capacity+ 0.15%NaCl,waterlogging +0.45%NaCl,25% of field capacity,25% of field capacity+ 0.15%NaCl,75% of field capacity+ 0.3%NaCl,75% of field capacity+ 0.45%NaCl,25% of field capacity+ 0.3%NaCl,50% of field capacity+ 0.3%NaCl,50% of field capacity+ 0.45%NaCl,and 25% of field capacity+ 0.45%NaCl,which had a poor growth.
    Interspecific competition between Trichogramma confusum and T.pretiosum on Corcyra cephaloica factitious eggs
    HE Yurong, LÜ Lihua, CHEN Kewei
    2004, (12):  2401-2404. 
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    By means of single and mixed inoculation,this paper studied the interspecific competition between T.confusum and T.pretiosum on the factitious eggs of Corcyra cephaloica under different parasitoid densities,host densities and inoculated spaces.The results showed that for both singly and mixed inoculated groups,the parasitism increased with parasitoid density but decreased with host density,whereas the percentage of female progeny dropped with parasitoid density but enhanced with host density.No significant effect was observed on adult emergence for all parasitoid and host density treatments.In mixed inoculated group,the proportion of T.pretiosum in the progeny decreased with parasitoid density but increased with host density,and was more than 50% in all treatments,indicating that T.pretiosum had a stronger competitive ability than T.confusum.In the spaces ranging from 4 cm3 to 102 cm3,the parasitism decreased gradually in both singly and mixed inoculated groups.The percentage of female progeny and adult emergence had no significant difference among different inoculated spaces.In mixed inoculated group,the proportion of T.pretiosum in the progeny was more than 50% in all treatments except space 102 cm3,but decreased with space,which suggested that T.confusum could improve their competitive ability through increasing their search areas and looking for more hosts.