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    15 March 2004, Volume 15 Issue 3
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    Community characteristics of Pinus armandi forest on Qinling Mountains
    WANG Dexiang, LIU Jianjun, LI Dengwu, LEI Ruide, LAN Guoyu
    2004, (3):  357-362. 
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    The community characteristics of Pinus armandi forest distributed on the mid-west zone of Qinling Mountains' south slope were investigated.The results showed that there were 166 seed plants belonging to 51 families,111generas.Among them,65 genera,66.7% of the total,belonged to temperate biome.There was a closely relationship between Pinus armandi forest and the temperate biome.As regards to the physiognomy of the community,phanerophyte made up 75.9% of the total,dominating the community.In the community,96 species with middle-sized leaves made up 57.8%,and there were 139 single leaf species,accounted for 83.7% of the total.There was a complicated vertical structure in the community,which could be divided into three layers:arbor layer,shrub layer and herb layer.In addition,there were also a lot of inter-stratum plants in the community.It is also found that the lack of seedlings,saplings and small trees was due to both the self-thinning caused by intra-specific competition and the alien-thinning by inter-specific competition for the light resource in the stand.The population of P.armandi was characterized with the patch size about 100 m2.The dynamics of the community showed that the community was stable and in a process of development.
    Analysis of Camellia rosthorniana populations fecundity
    CAO Guoxing, ZHONG Zhangcheng, XIE Deti, LIU Yun
    2004, (3):  363-366. 
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    With the method of space substituting time,the structure of Camellia rosthorniana populations in three forest communities,i.e,Jiant bamboo forest,coniferous and broad-leaved mixed forest,and evergreen broad-leaved forest in Mt.Jinyun was investigated,and based on static life-tables,the fecundity tables and reproductive value tables of C. rosthorniana populations were constructed.Each reproductive parameter and its relation to bionomic strategies of C. rosthorniana populations were also analyzed.The results indicated that in evergreen broad-leaved forest,C. rosthorniana population had the longest life span and the greatest fitness. The stage of maximum reproductive value increased with increasing stability of the community. The sum of each population's reproductive value,residual reproductive value and total reproductive value for the whole life-history of C. rosthorniana also increased with increasing maturity of the community,showing their inherent relationships with reproductive fitness.As regards to bionomic strategy,C. rosthorniana showed mainly the characteristics of a k-strategies,but in less stable community,the reproductive parameters were greatly changed,showing some characteristics of a r-strategies.
    Interspecies covariation analysis of dominant tree species in secondary succession of forest communities in Heishiding Natural Reserve,Guangdong Province
    ZHOU Xianye, WANG Bosun, LI Mingguang, CHEN Zhanghe
    2004, (3):  367-371. 
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    Based on a 2?2 contingency table,the Pearson product-moment correlation coefficient and Spearman rank correlation coefficient were used to analyses the interspecies covariation of dominant tree species in different communities of secondary succession series in Heishiding Natural Reserve,Guangdong Province.In early succession stage,14 pairs of tree species showed a significant interspecies covariation,and 9 pairs of species showed a negative coraviation,indicating that the species pairs needed the same habitats,while five pairs of species showed a positive covariation,which indicated that the species pairs needed different habitats.In the stage of needle broad-leaved mixed forest,only 5 pairs of species showed a significant interspecies covariation,and they were all positive covariation,which indicated the main species needed the same habitats and the interspecies competition were going.In the stage of evergreen broadleaved forest dominated by heliophytes,4 pairs of species showed a significant interspecies covariation,which was the least one in secondary succession series.Three pairs of them showed a positive covariation.It was the result of interspecies competition that the species pairs needed the same habitats.In the stage of evergreen broadleaved forest dominated by mesophytes,20 pairs of species showed a significant interspecies covariation,which was the most one in secondary succession series.Nineteen pairs of them showed a positive covariation.It showed positive covariation between species in upper tree layer and in middle or lower tree layer,but dominant species in upper tree layer had no significant interspecies covariation.
    Light energy utilization and dissipation in seedlings of three tropical rain forest tree species with different ecological habits
    ZHANG Jiaolin, CAO Kunfang
    2004, (3):  372-376. 
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    In this study,the light energy allocations between photochemical reactions and heat dissipation in the seedlings of three tropical rain forest tree species were investigated under three light regimes (100%,25% and 8% of full sunlight) by using chlorophyll fluorescence technique.These tree species are Anthocephalus chinensis (Rubiaceae),a pioneer species,Pometia tomentosa (Sapindaceae),a canopy climax species,and Horsfieldia tetratepala (Myristicaceae),a sub-canopy climax species.Under the same light levels,A.chinensis had a highermaximum photosynthetic rate (Pmax) and maximum electron transport rate (ETRmax) than P.tomentosa and H.tetratepala.From the light response curves of light energy allocations,all test species had a decreased fraction of light energy allocated to photochemical reactions,while the fraction of light energy allocated to heat dissipation was increased with light intensity.The fractions of light energy allocated to photochemical reactions and heat dissipation were negatively correlated with very high significance.Compared to other two species,A.chinensis allocated more light energy to fractions of photochemical reactions,and had weaker and unsaturated heat dissipation.But,when growing under 100% sunlight,this species had less excess light energy to be used for photosynthesis,so that,it did not suffer from photoinhibition.In contrast,more light energy was allocated to fractions of heat dissipation in both P.tomentosa and H.tetratepala seedlings.Growing under 100% sunlight,these two species received more excess light energy,which caused photoinhibition.Our results support the idea that light requirements for the regeneration of three tropical tree species under different ecological habits are related to their characteristics of light energy utilization and dissipation.
    Response of photosynthesis and antioxygenic enzymes in seedlings of three tropical forest tree species to different light environments
    GUO Xiaorong, CAO Kunfang, XU Zaifu
    2004, (3):  377-381. 
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    This paper studied the response of photosynthesis,chlorophyll a fluorescence and 3 antioxygenic enzyme activities in the seedlings of a pioneer species (Mallotus barbatus) and two endangered sub-canopy tree species (Litsea pierrei var.szemaois and L.dilleniifolia) in Xishuangbanna tropical rain forest to different light environments.Three light regimes (50%,25% and 8% full sunlight) were designed for the seedlings.The largest values of maximum photosynthetic rates (Pmax) of L.pierrei var.szemaois and L.dilleniifolia were documented at 25% and 8% sunlight,respectively,which showed that the two sub-canopy species had poor ability in photosynthetic acclimation to high light.In contrast,the Pmax of M.barbatus increased with light level.During a day,the maximum photochemical efficiency (Fv/Fm) of the photosystem Ⅱ in all the three species grown under three light levels showed minimum values at noon,and the lowest Fv/Fm values were shown in seedlings at 50% sunlight.Under 50% sunlight,the Fv/Fm values at dawn were lower in L.dilleniifolia than in the same species under other two light levels,indicating that sustained photoinhibition occurred in this case.The contents of malondialdehyde (MDA),H2O2,and activities of ascorbate peroxidase (APX),superoxide dismutase (SOD),catalase (CAT) of both L.pierrei var.szemaois and M.barbatus increased with stronger irradiance,which revealed that these two species were able to alleviate photodamage under high light stress by increasing their antioxigenic activities.But,high content of MDA revealed that L.dilleniifolia was probably suffered from membrane damage.In conclusion,our data revealed that the pioneer species M.barbatus had a high capacity to acclimate to different light environments,particularly high light,while the two subcanopy Litsea species had poor ability in acclimation to high light.Based on the findings of the present study,we suggest that the small populations and endangered status of both L.pierrei var.szemaois and L.dilleniifolia in natural environment could be partially due to their poor flexibility in response to changed light environment resulted from habitat fragmentation.
    Seasonal variations in biomass and salidroside content in roots of Rhodiola sachalinensis as affected by gauze and red film shading
    YAN Xiufeng, WANG Yang, GUO Shenglei, SHANG Xinhai
    2004, (3):  382-386. 
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    Rhodiola sachalinensis A.Bor,a perennial herb,belonging to the family Crassulaceae,is mainly distributed in mountains at the altitudes of 1 700～2 500 m.It is a typical alpine plant and a very important medicinal plant with high activities of anti-fatigue,anti-senescence,and anti-radiation,due to the secondary metabolite salidroside in its root.Our previous findings have proven that red light promotes salidroside synthesis remarkably but decreases biomass insignificantly,resulting in a higher yield of salidroside in roots of Rh.sachalinensis in a greenhouse.In order to investigate the influences of shading and red light on seasonal variations in biomass and salidroside content in Rh.sachalinensis roots,the effects on 3 or 4 years old Rh.sachalinensis plants in a nursery in Daxinganling Mountain (124°02' E,50°30' N) were studied in 2001.Compared to the control (CK) of full sunlight,6 treatments with neutral transparent film and gauze,or red film alone had been conducted for 131 days.In treatment Ⅰ,Rh.sachalinensis was shaded with neutral transparent film and gauze to achieve an irradiance 51.8% of full sunlight.In treatment II,the plants were shaded by red film alone,but the irradiance was as that in treatment I.In treatments Ⅲ,Ⅳ,Ⅴ and Ⅵ,neutral transparent film and gauze were originally used on May 8,then shifted to red film on Jun 3,July 4,August 4 and September 2,respectively and all experiments stopped on September 16,2001.Rh.sachalinensis roots were harvested on 2～4th from June to September and finally on September 16,and root-biomass and salidroside content were measured.Root-biomass in plants decreased significantly under shading with neutral transparent film and gauze compared to the control with full sunlight,but little variations in salidroside content and yield.In comparison with shading by neutral transparent film and gauze,root-biomass reduced lightly and salidroside content and yield in roots were increased remarkably under red-film shading.At the end of the season,salidroside content under red light was 163% in 3-year-old and 155% in 4-year-old Rh.sachalinensis roots;whereas salidroside yields were 144% in 3-year-old and 145% in 4-year-old Rh.sachalinensis roots to those in plants under shading.The results also showed that the enhancement in the salidroside content and yield were little related to the duration of red film shading,which implied that in order to increase salidroside content and get higher salidroside yield,but less affect root-biomass,Rh.sachalinensis may be shaded with red film just several days before harvest.
    Nitrogen cycling and its dynamic feature in fine roots of poplar trees and herbs
    FAN Shihua, LI Peizhi, WANG Lihua, XU Siming
    2004, (3):  387-390. 
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    The nitrogen cycling and its dynamic feature in fine roots of poplar trees and herbs were studied in Shenyang of Liaoning Province. The results showed that the nitrogen content in the standing biomass of fine roots of poplar trees and herbs was 20.3 kg穐m-2,and its net accumulation was 10.0 kg穐m-2. With regard to the biological cycling of nitrogen,the annual uptake was 14.6 kg穐m-2 of which,the retention and the return was 9. 6 and 5.1 kg穐m-2穣r-1 respectively,and the turnover period was 4 year. The relationship between total nitrogen in roots of poplar trees, and herbs and the available nitrogen in soil was also studied, which indicated that there were similar dynamic trends between total nitrogen in herb roots and the NH3-N in soil in growth season. The total nitrogen in fine roots of poplar trees was positively related to the biomass.
    Response of Dolichomitriopsis diversiformis photosynthesis rate to light,air temperature and plant water content
    LI Youji, LI Jing, CHEN Jun, HUANG Guowen
    2004, (3):  391-395. 
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    The net photosynthetic rate (Pn) of Dolichomitriopsis diversiformis(Mitt.) was measured under controlled air temperature (Ta),plant water content (PWC) and irradiance (Photosynthetically Active Radiation,PAR) in laboratory.The results showed that Pn was closely related to PAR,Ta and PWC.The response curve of Pn to PAR was a right angle hyperbola,and the parameters were affected by Ta and PWC.The Pn reduction was great when PWC was low and Ta was high,or when PWC was high and Ta was low.The peak Pn (Pmax) was observed underweak light (PAR<200 μmol·s-1·m-2) and relatively low (50%～80%) PWC.Under higher Ta,Pmax was higher,but decreased when Ta was higher than 25 ℃.The PWC range within which Pmax occurred increased in accordance with the increase of PAR.When PAR was lower than 200 μmol·s-1·m-2,the Ta range within which Pmax occurred was relatively high (20～25 ℃),and Pmax increased with the increase of PWC.When PWC was higher than 80%,Pmax decreased with the increase of PWC.The Ta range within which Pmax occurred decreased in accordance with the increase of PAR.Under moderate light (230<PAR<270 μmol·s-1·m-2),the sensitivity of Pn response to Ta and PWC was higher than that under higher or lower light.The Pn response to Ta and PWC was saddle-like,and its parameters were altered according to the variation in PAR.
    Characteristics analysis of micro-element contents in western Erdos soil and in Tetraena mongolica plant
    ZHI Yingbiao, YANG Chi, YAO Yiping, GAO Tianyun, HUANG Jie
    2004, (3):  396-400. 
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    This paper studied why the ex-situ conservation of Tetraena mongolica isn't successful.Through measuring and analyzing the micro-element contents in the soil where Tetraena mongolica is naturally distributed and where Tetraena mongolica is introduced in western Erdos.The results showed that among the areas where Tetraena mongolica is native to and the ex situ protection area,the average contents of 9 micro-elements,except B,are not only obviously higher than the average values in China's soil, but also higher than the values in desert areas.The contents of all micro-elements,except Cu,in the ex situ protection area are higher than desert and the natural distribution areas of Tetraena mongolica. Among the contents of the micro-elements in Tetraena mongolica plant,Fe,Cu,Zn,B,Se and Co are quite higher than that in other plant species on steppes,and Mo is higher than that in other plant species but is only 50% to the desert plants. The correlation coefficient for the contents of micro-elements between soil and plants (including adults and seedlings) are not significant and the contents in Tetraena mongolica plant are much higher than available contents of the counterparts in soil.By comparing the contents of micro-elements in Tetraena mongolica,grassland plants on steppe and desert and the contents in soil,it can be seen that every micro-element was enriched by Tetraena mongolica during its growth.The results do not support the suggestion that the contents of micro-elements in soil is the factor restricting the growth of Tetraena mongolica in the ex situ protection area.
    A preliminary study on burrow ecology of Manis pentadactyla
    WU Shibao, MA Guangzhi, CHEN Hai, XU Zhaorong, LI Youyu, LIU Naifa
    2004, (3):  401-407. 
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    A total of 61 pangolin(Manis pentadactyla)burrows at Dawuling Natural Reserve were recorded and measured from June 2000 to May 2001,and 40 of them were dissected.The results indicated that all the burrows were blind without branch.The long diameter of entrance was 14.20±2.79 cm(n=61),and the short one was 12.50±2.83 cm(n=61).These burrows could be divided into two types,i.e,winter burrows and summer burrows.Winter burrows were relatively deeper(1.44±0.73 m,n=28),and summer burrows were relatively shallower(0.32±0.11 m,n=12).The soil in burrows was usually soft,damp and thick,with a thick surface layer of organic matter.The main motive of digging burrows was to prey on termites,hibernate,rest,breed,hide,and defense.The mean residing duration of pangolin in a burrow was 12.25±2.25 d.Pangolin rarely utilized the used burrows,and the reutilization rate of used burrows was only 8.33%.The surroundings factors of 61 burrows were recorded,and divided into 9 categories and 27 subcategories.According to the occurrence frequency of each factor and the cluster analysis results of 61 burrows,the habitat selection of pangolin was discussed,which showed that pangolin preferred creating burrows at the sites with weak human disturbance(distance from disturbance source beyond 1 000 m),steep slope(30°～60°),half sunny and half shady slope,mixed coniferous and broadleaf forest,moderate elevation(760～1 500 m),good hiding conditions at entrance(full cover or partial cover),middle or lower slope location,and easily accessing to water source(distance from water source within 500 m).Pangolin was averse to establish burrows at the habitats with shady slope,poor hiding condition at entrance(bare),sharp steeper(>60°)or gentle(<30)slope,higher elevation(over 1 500 m),and coniferous forest.Pangolin preferred south facing,and strongly avoided north facing entrance.
    Growth and resource allocation pattern of Artemisia frigida under different grazing and clipping intensities
    LI Jinhua, LI Zhenqing, Liu Zhenguo
    2004, (3):  408-412. 
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    In order to understand the degradation process and its mechanism of typical steppe in Inner Mongolia,this paper studied the growth and resource allocation pattern of Artimisia frigida under different grazing and clipping intensities(no grazing,light grazing 1.33 sheep·hm-2,moderate grazing 4.00 sheep·hm-2,heavy grazing 6.67 sheep·hm-2,proportional clipping and stubble clipping),which was conducted at the Inner Mongolia Grassland Ecosystem Research Station of Chinese Academy of Sciences(43°26'～ 44°08'N,116°04'～117°05'E).The results showed that the regrowth ability of A.frigida under proportional clipping was superior to that under stubble clipping,and light clipping (1/4 proportional clipping or 10 cm stubble clipping) was superior to no clipping.In early growth season,the net regrowth of A.frigida was higher under no clipping than under light clipping,but reversed in late growth season (after mid-August).The biomass allocation pattern of A.frigida was roots>leaves>stems.Grazing or clipping affected biomass allocation significantly,especially for the allocation of leaves and flowers.The biomass allocation of leaves was significantly higher under 3/4 proportional clipping or 4 cm stubble clipping than under other treatments,and reverse trend was true for the biomass allocation of flowers.There were no significant differences in biomass allocation of roots and stems among treatments.Sexual reproductive allocation decreased with increasing grazing or clipping intensities,and reproductive mode of A.frigida changed under heavy grazing.The changes in priority of biomass allocation from sexual reproductive organs to clonal growth to sustain and propagate population were important ecological strategies of the species to heavy grazing.
    Effects of accumulated temperature and planting density on tillering dynamics of forage rye
    LI Zhijian, ZHOU Daowei, HU Yuegao
    2004, (3):  413-419. 
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    Using equal design method,a field experiment was carried out at Wuqiao field station of China Agricultural University in Hebei Province to study the effects of different accumulated temperature before winter and planting density on tillering dynamics of forage rye (Secale cereale L.).The results showed that the tiller number per plant was affected by sowing date and seed density.In the prophase of forage rye,the tiller number per plant was mainly influenced by sowing date;while in the anaphase,it was mainly determined by seed density. Generally,earlier and fewer sowing norm could raise the tiller number in individual plant.In the prophase,metaphase,or anaphase of forage rye,the tiller number per unit area decreased with the postponing of sowing date,and increased with the increase of sowing norm.The sowing date and sowing norm had decisive effect on the number of effective stem per unit area.Suitable population structure was dependent on the increase of effective stem number per plant under the conditions of earlier sowing,and of effective stem number per unit area under the conditions of later sowing.
    Effect of grazing on sandy grassland ecosystem in Inner Mongolia
    ZHAO Halin, ZHANG Tonghui, ZHAO Xueyong, ZHOU Ruilian
    2004, (3):  420-424. 
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    This experiment was carried out for 5 years in Horqin sandy land,Inner Mongolia,which had 4 treatments:Non-grazing (NG),light grazing (LG),moderate grazing (MG) and over grazing (OG).The results showed that different grazing intensities resulted in different development trend of the pasture ecosystem,of which,the injury of OG on pasture ecosystem was very great.The plant diversity,vegetation coverage,plant height and primary productivity under continuous overgrazing for 5 year were 87.9%,82.1%,94.0% and 57.0%,respectively,lower than those in NG.The biomass on the OG pasture was only 2.1% of NG,and the contents of soil clay,C and N as well as the quantities of soil microbes and small animals in OG were respectively 6.0%,31.9%,25.0%,95 0% and 75.9% lower than those in NG,but the soil hardness was raised by 274.0%.Especially,the secondary productivity of the pasture became negative from the third year,and the productive foundation of the pasture ecosystem was completely destroyed.Non-grazing was beneficial to pasture,and enclosure caused an increase in vegetation coverage,plant height and primary productivity.The vegetation coverage,plant height and soil status in LG and MG were not as good as those in NG,but were stable and didn't show worsening trend.Based on the above results,it's considered that on the sandy pasture in the semi-arid area of Inner Mongolia,the rational grass utilization ratio is 45%～50%,and the suitable loading capacity is 3～4 sheep unit·hm-2.
    Environmental quality assessment of regional agro-ecosystem in Loess Plateau
    WANG Limei, MENG Fanping, ZHENG Jiyong, WANG Zhonglin
    2004, (3):  425-428. 
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    Based on the detection and analysis of the contamination status of agro-ecosystem with apple-crops intercropping as the dominant cropping model in Loess Plateau,the individual factor and comprehensive environmental quality were assessed by multilevel fuzzy synthetic evaluation model,analytical hierarchy process(AHP),and improved standard weight deciding method.The results showed that the quality of soil,water and agricultural products was grade Ⅰ,the social economical environmental quality was grade Ⅱ,the ecological environmental quality was grade Ⅲ,and the comprehensive environmental quality was grade Ⅰ.The regional agro-ecosystem dominated by apple-crops intercropping was not the best model for the ecological benefits,but had the better social economical benefits.
    Temporal and spatial change of land use in Horqin Desert and its outer area
    ZHANG Yongmin, ZHAO Shidong
    2004, (3):  429-435. 
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    Based on two sets of land use data (1985 and 2000), the land use change in Horqin Desert and its outer area, in both spatial and temporal aspects, was studied with the tools of geographical information system (GIS) and statistics in this paper. Conclusions of this study are drawn as follows: From 1985 to 2000, the area order of individual land use changes was grassland>plough land>forestland>unused land>water body>residential and industrial land. As to the form of changes, the swapping area was greater than its quantitative change for forestland while the quantity change was greater, with different degree, than swap for the rest 5 land use types. As a whole, the quantity change was far greater than its swap. The analysis of land use dynamics showed that the speed of individual land use changes was in order of cultivated land>water body>grassland>forestland>unused land>residential and industrial land in sequence. Meanwhile, there was notable difference of land use change among counties in the region. For plough land change, Zhalute county was the greatest, Naiman the smallest. For forest change, Naiman was the greatest, Kalaqin the smallest. For grassland change, Tongliao city was the greatest, Alukerqin the smallest. For water change, Kezuozhongqi was the greatest, Balinzuoqi the smallest. For residential and industrial land change, Naiman was the greatest, Alukerqin the smallest. Finally, the change of unused land is more obvious in Chifeng city. As to the spatial change, 9 major land use change types were identified. Wherein, the change from grassland to plough land, expanding from the center of Horqin desert towards its outer counties, was still the most important land use change for the whole study area. In addition, the construction of protective forest for grassland in Naiman, the return from plough land to forestland in Kezuozhongqi, the return from plough land to grassland in Tongliao city, the deforestation for plough land in Kukun county, the degradation of grassland in Zhaluteqi, the exploit of river beach in Kailu, the reclamation of unused land in Kezuohouqi, and the regeneration of natural vegetation in Alukerqin were all important regional characteristics of land use change during the past 15 years.
    Distribution and characters of soil dry layer in north Shaanxi Loess Plateau
    WANG Li, SHAO Ming'an, ZHANG Qingfeng
    2004, (3):  436-442. 
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    Based on a whole survey and detailed analysis in artificial Robinnia pseudoscacia forestland,distribution and characters of dry layer in soil were studied in north Shaanxi Loess Platea.The results showed that soil dry layer was distributed universally from south to north in Loess Plateau,which can be classified into four zones according to the dryness:1)In southern gully zone represented by Ziwu Ridge and Huanglong Moutain in Yijun County,the soil dry layer was gentle,so if the appropriate measures were taken and water-saving facility were available or in water-abundant year,the shortage of soil water coull be alleviated;2)In northern gully zone represented by Fuxian and Huangling County,light soil dry layer occurs and was getting worse and we should pay close attention to this;3)In the large hill and gully zone,serious dry layer appears,it coull be subdivided into south,west and north plots.In south plot represented by Yanan and Yanchang County the dry layer was moderate;in west represented by Wuqi and Ansai County the dry layer was severe;in north represented by Suide and Mizhi County the dry layer was disastrous;4)In the windy sand zone represented by Shenmu County,since the precipitation decreased drastically and seriously sandy,very grave soil desiccation appeared.Also,soil dryness showed apparent horizontal differences with rainfall and the apparent vertical gradient in small hill area.
    Effect of soil tillage on phosphorus loss from slope land:An experimental study
    LI Yuyuan, SHAO Ming'an
    2004, (3):  443-448. 
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    Intensive soil erosion and nutrient loss from slope land not only resulted in the serious degradation of soil quality,but also threatened the water environment of the lower area.In this paper,a simulated rainfall experiment with loessial soil was conducted to study the characteristics of the loss of different phosphorus forms under the conditions of tillage and compaction(no-tillage).The results showed that in comparing with compaction,tillage increased the loss of dissolved P(DP),sediment extractable P(SEP)and sediment total P(STP)by 10 times due to the increase of runoff and sediment amount. The forms of the lost P were mainly sediment-combined P,and the ratios of DP/BAP and BAP/TP in the lost runoff were 12% and 2.6% under compaction,and 15% and 2.4% under tillage,respectively. The application of no-tillage or mulch-keeping fallow in Summer was effective to decrease soil and nutrient loss from slope land,which would be effective and significant both to soil degradation prevention and water environment protection in the lower area of Loess Plateau.
    Effect of incorporating corn residues into soil on nitrogen transformation in soil-plant ecosystem
    WANG Shuping, ZHOU Guangsheng, JIANG Yan, LIU Xiaoyi
    2004, (3):  449-452. 
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    Appropriate field management of crop residues can help to enhance soil productivity and nutrient recycling,and to minimize greenhouse gas emission.In this paper,a 15N tracer pot experiment was installed to study the effect of incorporating corn stalk and stubble into black soil on the nitrogen transformation in soil-plant ecosystem.The results indicated that compared with single application of N fertilizer,incorporation of corn stalk and stubble could increase soil nitrogen content and enhance its availability,and increase soil microbial nitrogen content.It also promoted the transfer of nitrogen in corn into its kernel,so as to increase the nitrogen use efficiency.Simultaneously,it reduced the content of soil NO3--N,and decreased the fertilizer nitrogen loss by 4.7～5.6%.
    Interactive effect of irrigation and nitrogen application on physiological characteristics of flag leaf and grain yield of winter wheat in dry years
    GUO Tiancai, FENG Wei, ZHAO Huijie, WANG Huacen, WANG Yonghua, XIA Guojun, MA Dongyun
    2004, (3):  453-457. 
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    The field studies indicated that in dry years,both irrigation and nitrogen application had a marked yield increment effect,but irrigation played a more important role.Irrigation at jointing and booting stages could induce a higher grain yield,but irrigation at jointing,booting and grain-filling stages had a less yield increment effect if nitrogen was applied as base fertilizer.Insufficient irrigation reduced the nitrogen efficiency and yield,which could be compensated to some extent by increasing the nitrogen application rate.Only a suitable combination of irrigation and nitrogen application could effectively coordinate the relationship between yield components and increase grain yield.
    Effect of reduced N application on N utilization and balance in winter wheat-summer maize cropping system
    LIU Xuejun, JU Xiaotang, ZHANG Fusuo
    2004, (3):  458-462. 
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    A field trial on a calcareous soil was carried out at an experimental station of China Agricultural University with the objective of assessing the effect of reduced nitrogen application on N utilization and N balance in a winter wheat-summer maize cropping system.Before this study,the trial has been conducted for one rotation cycle of wheat and maize with four-fixed N rates of 0,120,240 and 360 N kg·hm-2 per crop.In this study,each plot was divided into two sub-plots for two N application rates:normal N application(original rate) and reduced N application(reduced rate).The results showed that the grain yields of wheat and maize reached the platform at N rate of 120 kg·hm-2(N120),and then almost kept the same level regardless of the further increase of N rate(N240 and N 360).The N uptake by wheat and maize followed the similar tendency like their yield.The grain yield and N uptake of wheat were not significantly declined with the half reduction of original N rate except the treatment N 120.However,the same items in maize significantly declined with the further reduction of N fertilizer to zero.The residual NO3--N(main source of mineral N) in reduced N sub-plots was significantly lower in 0～1 m soil layer,but not different in 1～2 m soil layer compared with those receiving original N rate,indicating that 1～2 m soil NO3--N could hardly be utilized by crops.N balance calculation further showed that the N recovery by crops could be largely raised by the reduction of N fertilizer,while the apparent N loss rate decreased in wheat-maize rotation,respectively.Thus,the reduction of fertilizer N under high N rate can significantly increase N use efficiency and reduce NO3--N accumulation and apparent N loss.
    Microbial characteristics of straw-amended degraded soils in central Tibet and its effect on soil fertility
    CAI Xiaobu, QIAN Cheng, ZHANG Yuan, PU Qiong
    2004, (3):  463-468. 
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    This paper studied the dynamics of microbial communities in degraded soils of central Tibet under straw amendment and its effect on soil fertility.The results showed that straw amendment,and soil covering with spring highland barley (Hordeum vulgare var.nudum) straw in particular,could supply a beneficial soil environment for the relatively balanced growth of soil microbes,e.g,reduced water evaporation,appropriate temperature,and increased content of organic matter and nutrients.All the results demonstrated the possibility of straw amendment in recovering soil fertility and in reconstructing of soil structure in a relatively short period.
    Effect of crop-residue incorporation on soil CO2 emission and soil microbial biomass
    QIANG Xuecai, YUAN Hongli, GAO Wangsheng
    2004, (3):  469-472. 
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    In a wheat-corn cropping system, the crop residues were crushed and incorporated into soil after harvest. The soil respiration and soil microbial biomass were compared one year later with soil that had doubled amount of residues incorporation or had no incorporated residues. The soil respiration was increased by the residue incorporation and the effect was more apparent when the incorporated residue amount was doubled. The soil microbial biomass was also increased by the residue incorporation. But the effect of the incorporated residue quantity was not significant. Seasonally, the maximum soil respiration appeared earlier than the maximum microbial biomass, but soon turned to decrease. The microbial biomass maintained the high level for a longer period, indicating there was maintenance respiration and biosynthetic respiration as well. The residue incorporation was suggested as a measure to increase the soil fertility, but doubling the amount of residue incorporation seems not necessary.
    Repellent and antifeedant effect of secondary metabolites of non-host plants on Plutella xylostella
    WEI Hui, HOU Youming, YANG Guang, YOU Minsheng
    2004, (3):  473-476. 
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    Based on the theory of co-evolution between plants and phytophagous insects,the repellent and antifeedant effect of secondary metabolites of non-host plants on diamondback moth(DBM) Plutella xylostella was studied,aimed at finding out the oviposition repellents and antifeedants of insect pests.When the ethanol extracts(Etho Exts) of Bauhinia variegata,Eucalyptus tereticornis,Euphorbia hirta,Duranta repens,Zanthoxylum bungeanum,Magnolia grandiflora,and Nicotiana tabacum were applied respectively,the oviposition repellent rates were all over 80.00%;while after forty-eight hours treatment with the Etho Exts of Euphorbia pulcherrima,Broussonetia papyrifera,Artemisia argyi,Camellia oleifera,Salix babylonica,Euphorbia hirta,Bauhinia variegata,and Setaria viridisa,the antifeedant rates of DBM larvae were all more than 80.00%.
    Soil particle size fractionation with centrifugation method
    WU Tianyun, Jeff J. Schoenau, LI Fengmin, QIAN Peiyuan, WANG Fang, Sukhadev S. Malhi
    2004, (3):  477-481. 
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    According to the rotor size of Mandal RC5C and Stoks' law,a segregation procedure for soil particle size fractionation was designed,and used for the particle separation of Huangmian soil(Calcaric cambisols,FAO),Huihe soil(Haplic greyxems,FAO),and Helu soil(Calcic kastanozems,FAO) in the Loess Plateau of China,and of Orthic Brown Chernozem,and Orthic Black Chernozem in Canadian Prairie.The fractionation results of the 5 soils by using this procedure were in line with those of the standard pipette method.
    Effect of acetic acid on adsorption of acid phosphatase by some soil colloids and clay minerals
    ZHAO Zhenhua, HUANG Qiaoyun, JIANG Xin, YU Guifen, WANG Fang, LI Xueyuan
    2004, (3):  482-486. 
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    This paper studied the effect of acetic acid with different concentrations and pH values on the adsorption of acid phosphatase by some soil colloids and clay minerals (SCCM).The results showed that the pH values for the maximum adsorption of the enzyme were between the IEP of the enzyme and the PZC of SCCM.In the acetic acid systems,the amount of the enzyme adsorbed by SCCM was in the order of goethiteyellow brown soil>latosol>kaolinite>δ-MnO2.A remarkable influence of acetic acid concentration on the adsorption amount and the binding energy of the enzyme was observed.With the increase of the concentration from 0 to 200 mmol·L-1 in the system,acetic acid exhibited an enhanced effect,followed by an inhibition action on the adsorption of the enzyme on SCCM.The changes of the binding energy (K value) for the enzyme on SCCM were on the contrary to those of the maximum adsorption.The possible mechanisms for the influence of acetic acid on the adsorption of enzyme by SCCM were also discussed.
    Effects of different organic materials and their composting levels on soil microbial community
    KONG Weidong, LIU Kexing, LIAO Zongwen
    2004, (3):  487-492. 
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    In this paper,a pot experiment with tomato and different organic material amendment was installed in a greenhouse,and the diversity of soil microbial communities and their utilization pattern of amine,amino acid,carbohydrate,carboxylic acid,polymer and miscellaneous were assessed by Biolog method at 60 days after amendment.The results showed that organic material amendment could improve soil microbial community diversity.Fresh distiller grain amendment was a little bit better than its 10 days composting,and the composting level of cow manure had a significant positive or negative effect on the microbial diversity.Among the six carbon sources,the utilization of carbohydrate by soil microbial communities was the highest,and the microbial communities in soils amended with distiller grain had a significantly higher utilization of polymer,relative to those in soils amended with cow manure.
    Toxicity of surfactant,acid rain and Cd2+ combined pollution to the nucleus of Vicia faba root tip cells
    LIU Hongyu, LIAO Bohan, LU Shuangqing
    2004, (3):  493-496. 
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    The toxicity of Cd2+and its combination with surfactant or simulated acid rain to Vicia faba root tip cell was studied by using micro-nucleus technique. The results showed that the formation of micro-nucleus in Vicia faba root tip cell was strongly induced by Cd2+ in its concentration of 0～10.0 mg·L-1. The micro-nucleus rate was 13.85‰ at 6.0 mg·L-1Cd2+,4.53‰ at 0 mg·L-1 Cd2+,and the pollution index (PI) was 3.06. The micro-nucleus ratio and PI decreased when the accompanied surfactant LAS was also presented or the pH values decreased to 4.5 or 3.5. In the meantime,many deformed nuclei and grains were observed in the root tip cells. The growth of the Vicia faba roots was restrained, and the root cells were not easy to be scattered. Therefore,the toxicity of Cd2+ was increased by its combination with surfactant or acid rain. The Cd2+ toxicity to Vicia faba cells at pH3.5 was stronger than that at pH4.5. When the mutation effect of contaminant with high concentration or with strong toxicity to plant cell was tested, the contaminant should be diluted for at least three times,and hence, the highest micro-nucleus ratio and pollution index (PI) could be found.
    Effect of continual application of two kinds sludge on enzyme activities and heavy metal concentrations in alluvial soil
    TAN Qiling, HU Chengxiao, ZHAO Bin, R. G. Mclaren, CHENG Li, WU Lishu
    2004, (3):  497-500. 
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    Pot culture experiments were conducted to study the effect of industrial and sewage sludge on some enzyme activities and heavy metal concentrations in alluvial soil.The results showed that the heavy metals in both industrial and sewage sludge were mainly non-exchangeable,and those in sewage sludge had a lower concentration but a higher bio-availability than in industrial sludge.The application of sludge could increase the activities of soil urease,polyphenol oxidase and neutral phosphatase,and the polyphenol oxidase and neutral phosphatase activities showed a reverse relationship with the concentrations of soil exchangeable Zn and Cu.Soil polyphenol oxidase and catalase activities could be used to indicate the Zn pollution in soil.
    Affecting factors of CO2 evolution from biodegradation of agricultural organic wastes
    DU Jing, LIN Xianyong, ZHANG Yongsong
    2004, (3):  501-505. 
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    On the basis of a preliminary orthogonal design experiment,from which,the primary parameters suitable for the CO2 evolution from bio-degradation of agricultural organic wastes had been obtained,four single factor experiments were installed in greenhouse to seek the optimal parameters for the CO2 evolution.The results showed that the optimal parameters for the CO2 evolution from the bio-degradation of rice straw-pig manure mixture were 50 ℃,70% water content and initial pH 6.0～7.0.For fermentation,the optimal initial C/N ratio of substrate for cumulative CO2 evolution was 40/1,but 30/1 was better for compost.The effect of the four parameters on CO2 evolution was in the order of C/N ratio and water content>temperature>pH.
    Latest forty two years' sea surface temperature change of Weizhou Island and its influence on coral reef ecosystem
    YU Kefu, JIANG Mingxing, CHENG Zhiqiang, CHEN Tegu
    2004, (3):  506-510. 
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    Weizhou Island (109°00'～109°15'E,21°00'～21°10'N) locates in the north coral reef distribution belt of the South China Sea.In such relatively high latitude area,sea surface temperature (SST) is an important factor affecting the development of coral reef ecosystem.Measurements of the latest 42 years' SST of Weizhou Island showed that with 3～4 years and 7～8 years fluctuating cycles,the SST almost had a synchronous increase with global warming,especially since the later 1980s.Overall,the coral reef of Weizhou Island could benefit from the SST warming,especially the cold months SST increase,because it's the north margin of tropical zone.But,the warming of the warmest month may be a thermal stress on the development of coral reef.It reaches the upper limits of coral reef development,and leads the coral reef bleaching.Mankind activities,including wide scale building,oil gas factory near the island,traveling,fishing and breeding,may be also the potential stresses on limiting the coral reef development.The combination of summer warming and mankind stress is possibly to destroy the coral reef ecosystem of Weizhou Island.Based on a detailed field investigation,the modern coral reef distribution map around Weizhou Island was described.
    Research advance in nitrogen metabolism of plant and its environmental regulation
    XU Zhenzhu, ZHOU Guangsheng
    2004, (3):  511-516. 
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    Nitrogen metabolism is not only one of the basic processes of plant physiology,but also one of the important parts of global chemical cycle.Plant nitrogen assimilation directly takes part in the synthesis and conversion of amino acid through the reduction of nitrate.During this stage,some key enzymes,e.g,nitrate reductase (NR),glutamine systhetase (GS),glutamate dehydrogenase (GDH),glutamine synthase (GOGAT),aspargine synthetase (AS),and aspartate aminotransferase (AspAT) participate these processes.The protein is assimilated in plant cell through amino acid,and becomes a part of plant organism through modifying,classifying,transporting and storing processes,etc.The nitrogen metabolism is associated with carbonic metabolism through key enzyme regulations and the conversion of products,which consists of basic life process.Among these amino acids in plant cell,glutamic acid (Glu),glutamine (Gln),aspartic acid (Asp) and asparagines (Asn),etc,play a key role,which regulates their conversion each other and their contents in the plant cell through regulating formation and activity of those key enzymes.Environmental factors also affect the conversion and recycle of the key amino acids through regulating gene expression of the key enzymes and their activities.Nitrate and light intensity positively regulate the gene transcription of NR,but ammonium ions and Glu,Gln do the negative way.Water deficit is a very serious constraint on N2 fixation rate and soybean (Glycine max Merr.) grain yield,in which,ureide accumulation and degradation under water deficit appear to be the key issues of feedback mechanism on nitrogen fixation.Water stress decreases NR activity,but increases proteinase activity,and thus,they regulate plant nitrogen metabolism,although there are some different effects among species and cultivars.Water stress also decreases plant tissue protein content,ratio of protein and amino acid,and reduces the absorption of amino acid by plant.On the contrary,soil flooding decreases the content and accumulation amount of root nitrogen in winter wheat by 11.9% from booting to flowering stages and 39.1% during grain filling stage,and reduces the ratio of carbon and nitrogen by 79.6%.The results misadjust the metabolism between carbon and nitrogen,and result in the end of the root growth.Elevated CO2 level could decrease plant leaf nitrogen content under well-watered condition,but almost maintain stable under water deficit condition.The radiation of UV-B significantly reduces the partitioning coefficient and synthetic rate of Rubisco,which significantly decreases the photosynthetic rate.This paper reviewed the pathway of plant nitrogen assimilation,characteristics of key enzymes and their regulating mechanisms with picturing the regulating mode of NR,and described the signal sensing and conduct of plant nitrogen metabolism and the formation,transportation,storage and degradation of plant cell protein with picturing the schedule of protein transport of membrane system in plant cell.Seven key tasks are emphasized in this paper in terms of the review on the effects and mechanisms of key ecological factors including water stress on plant nitrogen metabolism.They are:1) the absorption mechanism of plant based on different nitrogen sources and environmental regulations,2) the localization and compartmentalization of the key enzymes of nitrogen mechanism in plant cell,3) the gene and environmental regulating model and their relationships in various key enzymes of nitrogen metabolism,4) the function of main cell organs and their responses to environmental factors in nitrogen metabolism process,5) physiological and chemical mechanism of nitrogen and the relationship between the mechanism and protein formation during crop grain filling,6) improving gene structure of special species or cultivars using gene engineering methods to enhance the resistance to environmental factor stress and the efficiency of absorption and transportation of nitrogen,and 7) the mechanism of natural nitrogen cycle and its response to human activity disturbance.
    Grazing resistance of rangeland plants
    WANG Shiping
    2004, (3):  517-522. 
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    Grazing resistance is the relative ability of plants to survive and grow in grazed systems,which can be divided into avoidance and tolerance components,based on the general mechanisms conferring resistance.The studies of resistance and tolerance thresholds will explain the reasons and mechanisms of grazing succession of plant communities.The difference of species resistant and tolerant thresholds depends on their grazing resistance strategies.Although both mechanisms are known to occur,the predominant mechanism or relative combination of mechanisms remains unknown for most species combinations and plant communities.Recognition of grazing avoidance or tolerance as the predominant resistance strategy inducing species composition shifts has important implications for grassland and pasture management.
    A review on types and mechanisms of compensation effect of crops under water deficit
    ZHAO Liying, DENG Xiping, SHAN Lun
    2004, (3):  523-526. 
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    In arid and semi-arid regions,the fact that crops suffering water deficit is unavoidable.Many studies indicated that plants have an ability to compensate the adverse effect of drought when the drought is moderate.But,how the compensation effects take place,and what are the physiological and biochemical mechanisms? This paper summarized the types,mechanisms and conditions of compensation effect that crops have under water deficit.The compensation effect is classified into growth compensation,physiological and biochemical compensation,and metabolism and output compensation.The biochemical and molecular mechanisms were discussed in terms of osmotic adjustment and dehydrate protection,and the biological basis of compensation effect was also elucidated.Finally,the direction for further study is pointed out.
    Research advance in ecosystem service of urban green space
    LI Feng, WANG Rusong
    2004, (3):  527-531. 
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    In this paper,the concept and connotation of urban green space and ecosystem service were expatiated,and the research advance in ecosystem service of urban green space was reviewed.The studies of ecosystem service of urban green space in overseas were focused on improving the quality of urban environment,maintaining biodiversity,providing amenity values,and ecosystem management;while in China,they were focused on the structure and function of urban green space,green quantity and quality,green equivalent,indicator system evaluation,value assessment,and application of CITYgreen model.The shortages and prospects of the researches on ecosystem service of urban green space were put forward.
    Impacts of cage culture on marine environment
    XU Yongjian, QIAN Lumin
    2004, (3):  532-536. 
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    The increasing production of sea food mainly depends on the developing mari-culture.Cage culture is intensive-culture and affects enormously their ambient waters.During the past 20 years,cage culture expended very rapidly,and the marine environment of cage area was worsen.This article reviews the impacts of cage culture on the aquatic environment,using studies published in the last 20 years.The impacts are numerous,including water pollution,impact on the sediment,genetic pollution,chemical pollution,and their resulting impacts on biodiversity in coastal sea.We present that we should give priority to study on the aquaculture and environment capacity in cage areas,and through utilizing the integrated culture restore the deteriorated culture environment.
    Dynamics of indole alkaloids in wheat varieties with various resistance to wheat aphid Sitobion avenae
    CAI Qingnian, WANG Yu, ZHANG Qingwen, ZHOU Mingzang
    2004, (3):  537-539. 
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    UV spectrometry measurement on the indole alkaloids (IA) contents of seven wheat varieties (KOK1679,My295,Li,Han4564 and Yanda1817,resistant to S. avenae;Shaanximazha and Lovrin10,susceptible to S. avenae) showed that during tillering and stem elongation stages,KOK1679,My295 and Li had a higher IA content (>0.5 mg穏-1 FW);and during heading and anthesis stages,the penultimate leaves of all five resistant varieties contained higher IA (>0.5 mg穏-1 FW).The IA content was lower in the flag leaves of both resistant and susceptible varieties,but was significantly higher in the ears of resistant varieties (up to 0.645 mg穏-1 FW in KOK1679) than in those of susceptible ones.It was showed that the IA content in wheat's ear played an important role in the resistance to S.avenae.
    Quantitative analysis of landscape patterns at the juncture of Shaanxi,Shanxi and Inner Mongolia,based on remote sensing data—Taking Yulin sheet TM image as an example
    LI Tuansheng
    2004, (3):  540-542. 
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    Based on the TM image of Yulin sheet and with the help of ERDAS,ARC/INFO and ARC/VIEW software,the landscape of Yulin sheet was classified.Using the spatial pattern analysis software FRAGSTATS of the vector version,a set of landscape indices were calculated at three scale levels of patches,classes and landscape.The results showed that landscape pattern indices could be successfully used in characterizing the spatial pattern of the studied area.However,this study should be further extended to the landscape of the same area in other period to analyze its dynamic change.FRAGSTATS was a good software,but should be improved by adding some indices such as PD2 developed by us.
    Community characteristics of Pinus armandi forest on Qinling Mountains
    WANG Dexiang, LIU Jianjun, LI Dengwu, LEI Ruide, LAN Guoyu
    2004, (3):  357-362. 
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    The community characteristics of Pinus armandi forest distributed on the mid-west zone of Qinling Mountains' south slope were investigated.The results showed that there were 166 seed plants belonging to 51 families,111generas.Among them,65 genera,66.7% of the total,belonged to temperate biome.There was a closely relationship between Pinus armandi forest and the temperate biome.As regards to the physiognomy of the community,phanerophyte made up 75.9% of the total,dominating the community.In the community,96 species with middle-sized leaves made up 57.8%,and there were 139 single leaf species,accounted for 83.7% of the total.There was a complicated vertical structure in the community,which could be divided into three layers:arbor layer,shrub layer and herb layer.In addition,there were also a lot of inter-stratum plants in the community.It is also found that the lack of seedlings,saplings and small trees was due to both the self-thinning caused by intra-specific competition and the alien-thinning by inter-specific competition for the light resource in the stand.The population of P.armandi was characterized with the patch size about 100 m2.The dynamics of the community showed that the community was stable and in a process of development.
    Analysis of Camellia rosthorniana populations fecundity
    CAO Guoxing, ZHONG Zhangcheng, XIE Deti, LIU Yun
    2004, (3):  363-366. 
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    With the method of space substituting time,the structure of Camellia rosthorniana populations in three forest communities,i.e,Jiant bamboo forest,coniferous and broad-leaved mixed forest,and evergreen broad-leaved forest in Mt.Jinyun was investigated,and based on static life-tables,the fecundity tables and reproductive value tables of C. rosthorniana populations were constructed.Each reproductive parameter and its relation to bionomic strategies of C. rosthorniana populations were also analyzed.The results indicated that in evergreen broad-leaved forest,C. rosthorniana population had the longest life span and the greatest fitness. The stage of maximum reproductive value increased with increasing stability of the community. The sum of each population's reproductive value,residual reproductive value and total reproductive value for the whole life-history of C. rosthorniana also increased with increasing maturity of the community,showing their inherent relationships with reproductive fitness.As regards to bionomic strategy,C. rosthorniana showed mainly the characteristics of a k-strategies,but in less stable community,the reproductive parameters were greatly changed,showing some characteristics of a r-strategies.
    Interspecies covariation analysis of dominant tree species in secondary succession of forest communities in Heishiding Natural Reserve,Guangdong Province
    ZHOU Xianye, WANG Bosun, LI Mingguang, CHEN Zhanghe
    2004, (3):  367-371. 
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    Based on a 2?2 contingency table,the Pearson product-moment correlation coefficient and Spearman rank correlation coefficient were used to analyses the interspecies covariation of dominant tree species in different communities of secondary succession series in Heishiding Natural Reserve,Guangdong Province.In early succession stage,14 pairs of tree species showed a significant interspecies covariation,and 9 pairs of species showed a negative coraviation,indicating that the species pairs needed the same habitats,while five pairs of species showed a positive covariation,which indicated that the species pairs needed different habitats.In the stage of needle broad-leaved mixed forest,only 5 pairs of species showed a significant interspecies covariation,and they were all positive covariation,which indicated the main species needed the same habitats and the interspecies competition were going.In the stage of evergreen broadleaved forest dominated by heliophytes,4 pairs of species showed a significant interspecies covariation,which was the least one in secondary succession series.Three pairs of them showed a positive covariation.It was the result of interspecies competition that the species pairs needed the same habitats.In the stage of evergreen broadleaved forest dominated by mesophytes,20 pairs of species showed a significant interspecies covariation,which was the most one in secondary succession series.Nineteen pairs of them showed a positive covariation.It showed positive covariation between species in upper tree layer and in middle or lower tree layer,but dominant species in upper tree layer had no significant interspecies covariation.
    Light energy utilization and dissipation in seedlings of three tropical rain forest tree species with different ecological habits
    ZHANG Jiaolin, CAO Kunfang
    2004, (3):  372-376. 
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    In this study,the light energy allocations between photochemical reactions and heat dissipation in the seedlings of three tropical rain forest tree species were investigated under three light regimes (100%,25% and 8% of full sunlight) by using chlorophyll fluorescence technique.These tree species are Anthocephalus chinensis (Rubiaceae),a pioneer species,Pometia tomentosa (Sapindaceae),a canopy climax species,and Horsfieldia tetratepala (Myristicaceae),a sub-canopy climax species.Under the same light levels,A.chinensis had a highermaximum photosynthetic rate (Pmax) and maximum electron transport rate (ETRmax) than P.tomentosa and H.tetratepala.From the light response curves of light energy allocations,all test species had a decreased fraction of light energy allocated to photochemical reactions,while the fraction of light energy allocated to heat dissipation was increased with light intensity.The fractions of light energy allocated to photochemical reactions and heat dissipation were negatively correlated with very high significance.Compared to other two species,A.chinensis allocated more light energy to fractions of photochemical reactions,and had weaker and unsaturated heat dissipation.But,when growing under 100% sunlight,this species had less excess light energy to be used for photosynthesis,so that,it did not suffer from photoinhibition.In contrast,more light energy was allocated to fractions of heat dissipation in both P.tomentosa and H.tetratepala seedlings.Growing under 100% sunlight,these two species received more excess light energy,which caused photoinhibition.Our results support the idea that light requirements for the regeneration of three tropical tree species under different ecological habits are related to their characteristics of light energy utilization and dissipation.
    Response of photosynthesis and antioxygenic enzymes in seedlings of three tropical forest tree species to different light environments
    GUO Xiaorong, CAO Kunfang, XU Zaifu
    2004, (3):  377-381. 
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    This paper studied the response of photosynthesis,chlorophyll a fluorescence and 3 antioxygenic enzyme activities in the seedlings of a pioneer species (Mallotus barbatus) and two endangered sub-canopy tree species (Litsea pierrei var.szemaois and L.dilleniifolia) in Xishuangbanna tropical rain forest to different light environments.Three light regimes (50%,25% and 8% full sunlight) were designed for the seedlings.The largest values of maximum photosynthetic rates (Pmax) of L.pierrei var.szemaois and L.dilleniifolia were documented at 25% and 8% sunlight,respectively,which showed that the two sub-canopy species had poor ability in photosynthetic acclimation to high light.In contrast,the Pmax of M.barbatus increased with light level.During a day,the maximum photochemical efficiency (Fv/Fm) of the photosystem Ⅱ in all the three species grown under three light levels showed minimum values at noon,and the lowest Fv/Fm values were shown in seedlings at 50% sunlight.Under 50% sunlight,the Fv/Fm values at dawn were lower in L.dilleniifolia than in the same species under other two light levels,indicating that sustained photoinhibition occurred in this case.The contents of malondialdehyde (MDA),H2O2,and activities of ascorbate peroxidase (APX),superoxide dismutase (SOD),catalase (CAT) of both L.pierrei var.szemaois and M.barbatus increased with stronger irradiance,which revealed that these two species were able to alleviate photodamage under high light stress by increasing their antioxigenic activities.But,high content of MDA revealed that L.dilleniifolia was probably suffered from membrane damage.In conclusion,our data revealed that the pioneer species M.barbatus had a high capacity to acclimate to different light environments,particularly high light,while the two subcanopy Litsea species had poor ability in acclimation to high light.Based on the findings of the present study,we suggest that the small populations and endangered status of both L.pierrei var.szemaois and L.dilleniifolia in natural environment could be partially due to their poor flexibility in response to changed light environment resulted from habitat fragmentation.
    Seasonal variations in biomass and salidroside content in roots of Rhodiola sachalinensis as affected by gauze and red film shading
    YAN Xiufeng, WANG Yang, GUO Shenglei, SHANG Xinhai
    2004, (3):  382-386. 
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    Rhodiola sachalinensis A.Bor,a perennial herb,belonging to the family Crassulaceae,is mainly distributed in mountains at the altitudes of 1 700～2 500 m.It is a typical alpine plant and a very important medicinal plant with high activities of anti-fatigue,anti-senescence,and anti-radiation,due to the secondary metabolite salidroside in its root.Our previous findings have proven that red light promotes salidroside synthesis remarkably but decreases biomass insignificantly,resulting in a higher yield of salidroside in roots of Rh.sachalinensis in a greenhouse.In order to investigate the influences of shading and red light on seasonal variations in biomass and salidroside content in Rh.sachalinensis roots,the effects on 3 or 4 years old Rh.sachalinensis plants in a nursery in Daxinganling Mountain (124°02' E,50°30' N) were studied in 2001.Compared to the control (CK) of full sunlight,6 treatments with neutral transparent film and gauze,or red film alone had been conducted for 131 days.In treatment Ⅰ,Rh.sachalinensis was shaded with neutral transparent film and gauze to achieve an irradiance 51.8% of full sunlight.In treatment II,the plants were shaded by red film alone,but the irradiance was as that in treatment I.In treatments Ⅲ,Ⅳ,Ⅴ and Ⅵ,neutral transparent film and gauze were originally used on May 8,then shifted to red film on Jun 3,July 4,August 4 and September 2,respectively and all experiments stopped on September 16,2001.Rh.sachalinensis roots were harvested on 2～4th from June to September and finally on September 16,and root-biomass and salidroside content were measured.Root-biomass in plants decreased significantly under shading with neutral transparent film and gauze compared to the control with full sunlight,but little variations in salidroside content and yield.In comparison with shading by neutral transparent film and gauze,root-biomass reduced lightly and salidroside content and yield in roots were increased remarkably under red-film shading.At the end of the season,salidroside content under red light was 163% in 3-year-old and 155% in 4-year-old Rh.sachalinensis roots;whereas salidroside yields were 144% in 3-year-old and 145% in 4-year-old Rh.sachalinensis roots to those in plants under shading.The results also showed that the enhancement in the salidroside content and yield were little related to the duration of red film shading,which implied that in order to increase salidroside content and get higher salidroside yield,but less affect root-biomass,Rh.sachalinensis may be shaded with red film just several days before harvest.
    Nitrogen cycling and its dynamic feature in fine roots of poplar trees and herbs
    FAN Shihua, LI Peizhi, WANG Lihua, XU Siming
    2004, (3):  387-390. 
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    The nitrogen cycling and its dynamic feature in fine roots of poplar trees and herbs were studied in Shenyang of Liaoning Province. The results showed that the nitrogen content in the standing biomass of fine roots of poplar trees and herbs was 20.3 kg穐m-2,and its net accumulation was 10.0 kg穐m-2. With regard to the biological cycling of nitrogen,the annual uptake was 14.6 kg穐m-2 of which,the retention and the return was 9. 6 and 5.1 kg穐m-2穣r-1 respectively,and the turnover period was 4 year. The relationship between total nitrogen in roots of poplar trees, and herbs and the available nitrogen in soil was also studied, which indicated that there were similar dynamic trends between total nitrogen in herb roots and the NH3-N in soil in growth season. The total nitrogen in fine roots of poplar trees was positively related to the biomass.
    Response of Dolichomitriopsis diversiformis photosynthesis rate to light,air temperature and plant water content
    LI Youji, LI Jing, CHEN Jun, HUANG Guowen
    2004, (3):  391-395. 
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    The net photosynthetic rate (Pn) of Dolichomitriopsis diversiformis(Mitt.) was measured under controlled air temperature (Ta),plant water content (PWC) and irradiance (Photosynthetically Active Radiation,PAR) in laboratory.The results showed that Pn was closely related to PAR,Ta and PWC.The response curve of Pn to PAR was a right angle hyperbola,and the parameters were affected by Ta and PWC.The Pn reduction was great when PWC was low and Ta was high,or when PWC was high and Ta was low.The peak Pn (Pmax) was observed underweak light (PAR<200 μmol·s-1·m-2) and relatively low (50%～80%) PWC.Under higher Ta,Pmax was higher,but decreased when Ta was higher than 25 ℃.The PWC range within which Pmax occurred increased in accordance with the increase of PAR.When PAR was lower than 200 μmol·s-1·m-2,the Ta range within which Pmax occurred was relatively high (20～25 ℃),and Pmax increased with the increase of PWC.When PWC was higher than 80%,Pmax decreased with the increase of PWC.The Ta range within which Pmax occurred decreased in accordance with the increase of PAR.Under moderate light (230<PAR<270 μmol·s-1·m-2),the sensitivity of Pn response to Ta and PWC was higher than that under higher or lower light.The Pn response to Ta and PWC was saddle-like,and its parameters were altered according to the variation in PAR.
    Characteristics analysis of micro-element contents in western Erdos soil and in Tetraena mongolica plant
    ZHI Yingbiao, YANG Chi, YAO Yiping, GAO Tianyun, HUANG Jie
    2004, (3):  396-400. 
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    This paper studied why the ex-situ conservation of Tetraena mongolica isn't successful.Through measuring and analyzing the micro-element contents in the soil where Tetraena mongolica is naturally distributed and where Tetraena mongolica is introduced in western Erdos.The results showed that among the areas where Tetraena mongolica is native to and the ex situ protection area,the average contents of 9 micro-elements,except B,are not only obviously higher than the average values in China's soil, but also higher than the values in desert areas.The contents of all micro-elements,except Cu,in the ex situ protection area are higher than desert and the natural distribution areas of Tetraena mongolica. Among the contents of the micro-elements in Tetraena mongolica plant,Fe,Cu,Zn,B,Se and Co are quite higher than that in other plant species on steppes,and Mo is higher than that in other plant species but is only 50% to the desert plants. The correlation coefficient for the contents of micro-elements between soil and plants (including adults and seedlings) are not significant and the contents in Tetraena mongolica plant are much higher than available contents of the counterparts in soil.By comparing the contents of micro-elements in Tetraena mongolica,grassland plants on steppe and desert and the contents in soil,it can be seen that every micro-element was enriched by Tetraena mongolica during its growth.The results do not support the suggestion that the contents of micro-elements in soil is the factor restricting the growth of Tetraena mongolica in the ex situ protection area.
    A preliminary study on burrow ecology of Manis pentadactyla
    WU Shibao, MA Guangzhi, CHEN Hai, XU Zhaorong, LI Youyu, LIU Naifa
    2004, (3):  401-407. 
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    A total of 61 pangolin(Manis pentadactyla)burrows at Dawuling Natural Reserve were recorded and measured from June 2000 to May 2001,and 40 of them were dissected.The results indicated that all the burrows were blind without branch.The long diameter of entrance was 14.20±2.79 cm(n=61),and the short one was 12.50±2.83 cm(n=61).These burrows could be divided into two types,i.e,winter burrows and summer burrows.Winter burrows were relatively deeper(1.44±0.73 m,n=28),and summer burrows were relatively shallower(0.32±0.11 m,n=12).The soil in burrows was usually soft,damp and thick,with a thick surface layer of organic matter.The main motive of digging burrows was to prey on termites,hibernate,rest,breed,hide,and defense.The mean residing duration of pangolin in a burrow was 12.25±2.25 d.Pangolin rarely utilized the used burrows,and the reutilization rate of used burrows was only 8.33%.The surroundings factors of 61 burrows were recorded,and divided into 9 categories and 27 subcategories.According to the occurrence frequency of each factor and the cluster analysis results of 61 burrows,the habitat selection of pangolin was discussed,which showed that pangolin preferred creating burrows at the sites with weak human disturbance(distance from disturbance source beyond 1 000 m),steep slope(30°～60°),half sunny and half shady slope,mixed coniferous and broadleaf forest,moderate elevation(760～1 500 m),good hiding conditions at entrance(full cover or partial cover),middle or lower slope location,and easily accessing to water source(distance from water source within 500 m).Pangolin was averse to establish burrows at the habitats with shady slope,poor hiding condition at entrance(bare),sharp steeper(>60°)or gentle(<30)slope,higher elevation(over 1 500 m),and coniferous forest.Pangolin preferred south facing,and strongly avoided north facing entrance.
    Growth and resource allocation pattern of Artemisia frigida under different grazing and clipping intensities
    LI Jinhua, LI Zhenqing, Liu Zhenguo
    2004, (3):  408-412. 
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    In order to understand the degradation process and its mechanism of typical steppe in Inner Mongolia,this paper studied the growth and resource allocation pattern of Artimisia frigida under different grazing and clipping intensities(no grazing,light grazing 1.33 sheep·hm-2,moderate grazing 4.00 sheep·hm-2,heavy grazing 6.67 sheep·hm-2,proportional clipping and stubble clipping),which was conducted at the Inner Mongolia Grassland Ecosystem Research Station of Chinese Academy of Sciences(43°26'～ 44°08'N,116°04'～117°05'E).The results showed that the regrowth ability of A.frigida under proportional clipping was superior to that under stubble clipping,and light clipping (1/4 proportional clipping or 10 cm stubble clipping) was superior to no clipping.In early growth season,the net regrowth of A.frigida was higher under no clipping than under light clipping,but reversed in late growth season (after mid-August).The biomass allocation pattern of A.frigida was roots>leaves>stems.Grazing or clipping affected biomass allocation significantly,especially for the allocation of leaves and flowers.The biomass allocation of leaves was significantly higher under 3/4 proportional clipping or 4 cm stubble clipping than under other treatments,and reverse trend was true for the biomass allocation of flowers.There were no significant differences in biomass allocation of roots and stems among treatments.Sexual reproductive allocation decreased with increasing grazing or clipping intensities,and reproductive mode of A.frigida changed under heavy grazing.The changes in priority of biomass allocation from sexual reproductive organs to clonal growth to sustain and propagate population were important ecological strategies of the species to heavy grazing.
    Effects of accumulated temperature and planting density on tillering dynamics of forage rye
    LI Zhijian, ZHOU Daowei, HU Yuegao
    2004, (3):  413-419. 
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    Using equal design method,a field experiment was carried out at Wuqiao field station of China Agricultural University in Hebei Province to study the effects of different accumulated temperature before winter and planting density on tillering dynamics of forage rye (Secale cereale L.).The results showed that the tiller number per plant was affected by sowing date and seed density.In the prophase of forage rye,the tiller number per plant was mainly influenced by sowing date;while in the anaphase,it was mainly determined by seed density. Generally,earlier and fewer sowing norm could raise the tiller number in individual plant.In the prophase,metaphase,or anaphase of forage rye,the tiller number per unit area decreased with the postponing of sowing date,and increased with the increase of sowing norm.The sowing date and sowing norm had decisive effect on the number of effective stem per unit area.Suitable population structure was dependent on the increase of effective stem number per plant under the conditions of earlier sowing,and of effective stem number per unit area under the conditions of later sowing.
    Effect of grazing on sandy grassland ecosystem in Inner Mongolia
    ZHAO Halin, ZHANG Tonghui, ZHAO Xueyong, ZHOU Ruilian
    2004, (3):  420-424. 
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    This experiment was carried out for 5 years in Horqin sandy land,Inner Mongolia,which had 4 treatments:Non-grazing (NG),light grazing (LG),moderate grazing (MG) and over grazing (OG).The results showed that different grazing intensities resulted in different development trend of the pasture ecosystem,of which,the injury of OG on pasture ecosystem was very great.The plant diversity,vegetation coverage,plant height and primary productivity under continuous overgrazing for 5 year were 87.9%,82.1%,94.0% and 57.0%,respectively,lower than those in NG.The biomass on the OG pasture was only 2.1% of NG,and the contents of soil clay,C and N as well as the quantities of soil microbes and small animals in OG were respectively 6.0%,31.9%,25.0%,95 0% and 75.9% lower than those in NG,but the soil hardness was raised by 274.0%.Especially,the secondary productivity of the pasture became negative from the third year,and the productive foundation of the pasture ecosystem was completely destroyed.Non-grazing was beneficial to pasture,and enclosure caused an increase in vegetation coverage,plant height and primary productivity.The vegetation coverage,plant height and soil status in LG and MG were not as good as those in NG,but were stable and didn't show worsening trend.Based on the above results,it's considered that on the sandy pasture in the semi-arid area of Inner Mongolia,the rational grass utilization ratio is 45%～50%,and the suitable loading capacity is 3～4 sheep unit·hm-2.
    Environmental quality assessment of regional agro-ecosystem in Loess Plateau
    WANG Limei, MENG Fanping, ZHENG Jiyong, WANG Zhonglin
    2004, (3):  425-428. 
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    Based on the detection and analysis of the contamination status of agro-ecosystem with apple-crops intercropping as the dominant cropping model in Loess Plateau,the individual factor and comprehensive environmental quality were assessed by multilevel fuzzy synthetic evaluation model,analytical hierarchy process(AHP),and improved standard weight deciding method.The results showed that the quality of soil,water and agricultural products was grade Ⅰ,the social economical environmental quality was grade Ⅱ,the ecological environmental quality was grade Ⅲ,and the comprehensive environmental quality was grade Ⅰ.The regional agro-ecosystem dominated by apple-crops intercropping was not the best model for the ecological benefits,but had the better social economical benefits.
    Temporal and spatial change of land use in Horqin Desert and its outer area
    ZHANG Yongmin, ZHAO Shidong
    2004, (3):  429-435. 
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    Based on two sets of land use data (1985 and 2000), the land use change in Horqin Desert and its outer area, in both spatial and temporal aspects, was studied with the tools of geographical information system (GIS) and statistics in this paper. Conclusions of this study are drawn as follows: From 1985 to 2000, the area order of individual land use changes was grassland>plough land>forestland>unused land>water body>residential and industrial land. As to the form of changes, the swapping area was greater than its quantitative change for forestland while the quantity change was greater, with different degree, than swap for the rest 5 land use types. As a whole, the quantity change was far greater than its swap. The analysis of land use dynamics showed that the speed of individual land use changes was in order of cultivated land>water body>grassland>forestland>unused land>residential and industrial land in sequence. Meanwhile, there was notable difference of land use change among counties in the region. For plough land change, Zhalute county was the greatest, Naiman the smallest. For forest change, Naiman was the greatest, Kalaqin the smallest. For grassland change, Tongliao city was the greatest, Alukerqin the smallest. For water change, Kezuozhongqi was the greatest, Balinzuoqi the smallest. For residential and industrial land change, Naiman was the greatest, Alukerqin the smallest. Finally, the change of unused land is more obvious in Chifeng city. As to the spatial change, 9 major land use change types were identified. Wherein, the change from grassland to plough land, expanding from the center of Horqin desert towards its outer counties, was still the most important land use change for the whole study area. In addition, the construction of protective forest for grassland in Naiman, the return from plough land to forestland in Kezuozhongqi, the return from plough land to grassland in Tongliao city, the deforestation for plough land in Kukun county, the degradation of grassland in Zhaluteqi, the exploit of river beach in Kailu, the reclamation of unused land in Kezuohouqi, and the regeneration of natural vegetation in Alukerqin were all important regional characteristics of land use change during the past 15 years.
    Distribution and characters of soil dry layer in north Shaanxi Loess Plateau
    WANG Li, SHAO Ming'an, ZHANG Qingfeng
    2004, (3):  436-442. 
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    Based on a whole survey and detailed analysis in artificial Robinnia pseudoscacia forestland,distribution and characters of dry layer in soil were studied in north Shaanxi Loess Platea.The results showed that soil dry layer was distributed universally from south to north in Loess Plateau,which can be classified into four zones according to the dryness:1)In southern gully zone represented by Ziwu Ridge and Huanglong Moutain in Yijun County,the soil dry layer was gentle,so if the appropriate measures were taken and water-saving facility were available or in water-abundant year,the shortage of soil water coull be alleviated;2)In northern gully zone represented by Fuxian and Huangling County,light soil dry layer occurs and was getting worse and we should pay close attention to this;3)In the large hill and gully zone,serious dry layer appears,it coull be subdivided into south,west and north plots.In south plot represented by Yanan and Yanchang County the dry layer was moderate;in west represented by Wuqi and Ansai County the dry layer was severe;in north represented by Suide and Mizhi County the dry layer was disastrous;4)In the windy sand zone represented by Shenmu County,since the precipitation decreased drastically and seriously sandy,very grave soil desiccation appeared.Also,soil dryness showed apparent horizontal differences with rainfall and the apparent vertical gradient in small hill area.
    Effect of soil tillage on phosphorus loss from slope land:An experimental study
    LI Yuyuan, SHAO Ming'an
    2004, (3):  443-448. 
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    Intensive soil erosion and nutrient loss from slope land not only resulted in the serious degradation of soil quality,but also threatened the water environment of the lower area.In this paper,a simulated rainfall experiment with loessial soil was conducted to study the characteristics of the loss of different phosphorus forms under the conditions of tillage and compaction(no-tillage).The results showed that in comparing with compaction,tillage increased the loss of dissolved P(DP),sediment extractable P(SEP)and sediment total P(STP)by 10 times due to the increase of runoff and sediment amount. The forms of the lost P were mainly sediment-combined P,and the ratios of DP/BAP and BAP/TP in the lost runoff were 12% and 2.6% under compaction,and 15% and 2.4% under tillage,respectively. The application of no-tillage or mulch-keeping fallow in Summer was effective to decrease soil and nutrient loss from slope land,which would be effective and significant both to soil degradation prevention and water environment protection in the lower area of Loess Plateau.
    Effect of incorporating corn residues into soil on nitrogen transformation in soil-plant ecosystem
    WANG Shuping, ZHOU Guangsheng, JIANG Yan, LIU Xiaoyi
    2004, (3):  449-452. 
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    Appropriate field management of crop residues can help to enhance soil productivity and nutrient recycling,and to minimize greenhouse gas emission.In this paper,a 15N tracer pot experiment was installed to study the effect of incorporating corn stalk and stubble into black soil on the nitrogen transformation in soil-plant ecosystem.The results indicated that compared with single application of N fertilizer,incorporation of corn stalk and stubble could increase soil nitrogen content and enhance its availability,and increase soil microbial nitrogen content.It also promoted the transfer of nitrogen in corn into its kernel,so as to increase the nitrogen use efficiency.Simultaneously,it reduced the content of soil NO3--N,and decreased the fertilizer nitrogen loss by 4.7～5.6%.
    Interactive effect of irrigation and nitrogen application on physiological characteristics of flag leaf and grain yield of winter wheat in dry years
    GUO Tiancai, FENG Wei, ZHAO Huijie, WANG Huacen, WANG Yonghua, XIA Guojun, MA Dongyun
    2004, (3):  453-457. 
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    The field studies indicated that in dry years,both irrigation and nitrogen application had a marked yield increment effect,but irrigation played a more important role.Irrigation at jointing and booting stages could induce a higher grain yield,but irrigation at jointing,booting and grain-filling stages had a less yield increment effect if nitrogen was applied as base fertilizer.Insufficient irrigation reduced the nitrogen efficiency and yield,which could be compensated to some extent by increasing the nitrogen application rate.Only a suitable combination of irrigation and nitrogen application could effectively coordinate the relationship between yield components and increase grain yield.
    Effect of reduced N application on N utilization and balance in winter wheat-summer maize cropping system
    LIU Xuejun, JU Xiaotang, ZHANG Fusuo
    2004, (3):  458-462. 
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    A field trial on a calcareous soil was carried out at an experimental station of China Agricultural University with the objective of assessing the effect of reduced nitrogen application on N utilization and N balance in a winter wheat-summer maize cropping system.Before this study,the trial has been conducted for one rotation cycle of wheat and maize with four-fixed N rates of 0,120,240 and 360 N kg·hm-2 per crop.In this study,each plot was divided into two sub-plots for two N application rates:normal N application(original rate) and reduced N application(reduced rate).The results showed that the grain yields of wheat and maize reached the platform at N rate of 120 kg·hm-2(N120),and then almost kept the same level regardless of the further increase of N rate(N240 and N 360).The N uptake by wheat and maize followed the similar tendency like their yield.The grain yield and N uptake of wheat were not significantly declined with the half reduction of original N rate except the treatment N 120.However,the same items in maize significantly declined with the further reduction of N fertilizer to zero.The residual NO3--N(main source of mineral N) in reduced N sub-plots was significantly lower in 0～1 m soil layer,but not different in 1～2 m soil layer compared with those receiving original N rate,indicating that 1～2 m soil NO3--N could hardly be utilized by crops.N balance calculation further showed that the N recovery by crops could be largely raised by the reduction of N fertilizer,while the apparent N loss rate decreased in wheat-maize rotation,respectively.Thus,the reduction of fertilizer N under high N rate can significantly increase N use efficiency and reduce NO3--N accumulation and apparent N loss.
    Microbial characteristics of straw-amended degraded soils in central Tibet and its effect on soil fertility
    CAI Xiaobu, QIAN Cheng, ZHANG Yuan, PU Qiong
    2004, (3):  463-468. 
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    This paper studied the dynamics of microbial communities in degraded soils of central Tibet under straw amendment and its effect on soil fertility.The results showed that straw amendment,and soil covering with spring highland barley (Hordeum vulgare var.nudum) straw in particular,could supply a beneficial soil environment for the relatively balanced growth of soil microbes,e.g,reduced water evaporation,appropriate temperature,and increased content of organic matter and nutrients.All the results demonstrated the possibility of straw amendment in recovering soil fertility and in reconstructing of soil structure in a relatively short period.
    Effect of crop-residue incorporation on soil CO2 emission and soil microbial biomass
    QIANG Xuecai, YUAN Hongli, GAO Wangsheng
    2004, (3):  469-472. 
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    In a wheat-corn cropping system, the crop residues were crushed and incorporated into soil after harvest. The soil respiration and soil microbial biomass were compared one year later with soil that had doubled amount of residues incorporation or had no incorporated residues. The soil respiration was increased by the residue incorporation and the effect was more apparent when the incorporated residue amount was doubled. The soil microbial biomass was also increased by the residue incorporation. But the effect of the incorporated residue quantity was not significant. Seasonally, the maximum soil respiration appeared earlier than the maximum microbial biomass, but soon turned to decrease. The microbial biomass maintained the high level for a longer period, indicating there was maintenance respiration and biosynthetic respiration as well. The residue incorporation was suggested as a measure to increase the soil fertility, but doubling the amount of residue incorporation seems not necessary.
    Repellent and antifeedant effect of secondary metabolites of non-host plants on Plutella xylostella
    WEI Hui, HOU Youming, YANG Guang, YOU Minsheng
    2004, (3):  473-476. 
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    Based on the theory of co-evolution between plants and phytophagous insects,the repellent and antifeedant effect of secondary metabolites of non-host plants on diamondback moth(DBM) Plutella xylostella was studied,aimed at finding out the oviposition repellents and antifeedants of insect pests.When the ethanol extracts(Etho Exts) of Bauhinia variegata,Eucalyptus tereticornis,Euphorbia hirta,Duranta repens,Zanthoxylum bungeanum,Magnolia grandiflora,and Nicotiana tabacum were applied respectively,the oviposition repellent rates were all over 80.00%;while after forty-eight hours treatment with the Etho Exts of Euphorbia pulcherrima,Broussonetia papyrifera,Artemisia argyi,Camellia oleifera,Salix babylonica,Euphorbia hirta,Bauhinia variegata,and Setaria viridisa,the antifeedant rates of DBM larvae were all more than 80.00%.
    Soil particle size fractionation with centrifugation method
    WU Tianyun, Jeff J. Schoenau, LI Fengmin, QIAN Peiyuan, WANG Fang, Sukhadev S. Malhi
    2004, (3):  477-481. 
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    According to the rotor size of Mandal RC5C and Stoks' law,a segregation procedure for soil particle size fractionation was designed,and used for the particle separation of Huangmian soil(Calcaric cambisols,FAO),Huihe soil(Haplic greyxems,FAO),and Helu soil(Calcic kastanozems,FAO) in the Loess Plateau of China,and of Orthic Brown Chernozem,and Orthic Black Chernozem in Canadian Prairie.The fractionation results of the 5 soils by using this procedure were in line with those of the standard pipette method.
    Effect of acetic acid on adsorption of acid phosphatase by some soil colloids and clay minerals
    ZHAO Zhenhua, HUANG Qiaoyun, JIANG Xin, YU Guifen, WANG Fang, LI Xueyuan
    2004, (3):  482-486. 
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    This paper studied the effect of acetic acid with different concentrations and pH values on the adsorption of acid phosphatase by some soil colloids and clay minerals (SCCM).The results showed that the pH values for the maximum adsorption of the enzyme were between the IEP of the enzyme and the PZC of SCCM.In the acetic acid systems,the amount of the enzyme adsorbed by SCCM was in the order of goethiteyellow brown soil>latosol>kaolinite>δ-MnO2.A remarkable influence of acetic acid concentration on the adsorption amount and the binding energy of the enzyme was observed.With the increase of the concentration from 0 to 200 mmol·L-1 in the system,acetic acid exhibited an enhanced effect,followed by an inhibition action on the adsorption of the enzyme on SCCM.The changes of the binding energy (K value) for the enzyme on SCCM were on the contrary to those of the maximum adsorption.The possible mechanisms for the influence of acetic acid on the adsorption of enzyme by SCCM were also discussed.
    Effects of different organic materials and their composting levels on soil microbial community
    KONG Weidong, LIU Kexing, LIAO Zongwen
    2004, (3):  487-492. 
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    In this paper,a pot experiment with tomato and different organic material amendment was installed in a greenhouse,and the diversity of soil microbial communities and their utilization pattern of amine,amino acid,carbohydrate,carboxylic acid,polymer and miscellaneous were assessed by Biolog method at 60 days after amendment.The results showed that organic material amendment could improve soil microbial community diversity.Fresh distiller grain amendment was a little bit better than its 10 days composting,and the composting level of cow manure had a significant positive or negative effect on the microbial diversity.Among the six carbon sources,the utilization of carbohydrate by soil microbial communities was the highest,and the microbial communities in soils amended with distiller grain had a significantly higher utilization of polymer,relative to those in soils amended with cow manure.
    Toxicity of surfactant,acid rain and Cd2+ combined pollution to the nucleus of Vicia faba root tip cells
    LIU Hongyu, LIAO Bohan, LU Shuangqing
    2004, (3):  493-496. 
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    The toxicity of Cd2+and its combination with surfactant or simulated acid rain to Vicia faba root tip cell was studied by using micro-nucleus technique. The results showed that the formation of micro-nucleus in Vicia faba root tip cell was strongly induced by Cd2+ in its concentration of 0～10.0 mg·L-1. The micro-nucleus rate was 13.85‰ at 6.0 mg·L-1Cd2+,4.53‰ at 0 mg·L-1 Cd2+,and the pollution index (PI) was 3.06. The micro-nucleus ratio and PI decreased when the accompanied surfactant LAS was also presented or the pH values decreased to 4.5 or 3.5. In the meantime,many deformed nuclei and grains were observed in the root tip cells. The growth of the Vicia faba roots was restrained, and the root cells were not easy to be scattered. Therefore,the toxicity of Cd2+ was increased by its combination with surfactant or acid rain. The Cd2+ toxicity to Vicia faba cells at pH3.5 was stronger than that at pH4.5. When the mutation effect of contaminant with high concentration or with strong toxicity to plant cell was tested, the contaminant should be diluted for at least three times,and hence, the highest micro-nucleus ratio and pollution index (PI) could be found.
    Effect of continual application of two kinds sludge on enzyme activities and heavy metal concentrations in alluvial soil
    TAN Qiling, HU Chengxiao, ZHAO Bin, R. G. Mclaren, CHENG Li, WU Lishu
    2004, (3):  497-500. 
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    Pot culture experiments were conducted to study the effect of industrial and sewage sludge on some enzyme activities and heavy metal concentrations in alluvial soil.The results showed that the heavy metals in both industrial and sewage sludge were mainly non-exchangeable,and those in sewage sludge had a lower concentration but a higher bio-availability than in industrial sludge.The application of sludge could increase the activities of soil urease,polyphenol oxidase and neutral phosphatase,and the polyphenol oxidase and neutral phosphatase activities showed a reverse relationship with the concentrations of soil exchangeable Zn and Cu.Soil polyphenol oxidase and catalase activities could be used to indicate the Zn pollution in soil.
    Affecting factors of CO2 evolution from biodegradation of agricultural organic wastes
    DU Jing, LIN Xianyong, ZHANG Yongsong
    2004, (3):  501-505. 
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    On the basis of a preliminary orthogonal design experiment,from which,the primary parameters suitable for the CO2 evolution from bio-degradation of agricultural organic wastes had been obtained,four single factor experiments were installed in greenhouse to seek the optimal parameters for the CO2 evolution.The results showed that the optimal parameters for the CO2 evolution from the bio-degradation of rice straw-pig manure mixture were 50 ℃,70% water content and initial pH 6.0～7.0.For fermentation,the optimal initial C/N ratio of substrate for cumulative CO2 evolution was 40/1,but 30/1 was better for compost.The effect of the four parameters on CO2 evolution was in the order of C/N ratio and water content>temperature>pH.
    Latest forty two years' sea surface temperature change of Weizhou Island and its influence on coral reef ecosystem
    YU Kefu, JIANG Mingxing, CHENG Zhiqiang, CHEN Tegu
    2004, (3):  506-510. 
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    Weizhou Island (109°00'～109°15'E,21°00'～21°10'N) locates in the north coral reef distribution belt of the South China Sea.In such relatively high latitude area,sea surface temperature (SST) is an important factor affecting the development of coral reef ecosystem.Measurements of the latest 42 years' SST of Weizhou Island showed that with 3～4 years and 7～8 years fluctuating cycles,the SST almost had a synchronous increase with global warming,especially since the later 1980s.Overall,the coral reef of Weizhou Island could benefit from the SST warming,especially the cold months SST increase,because it's the north margin of tropical zone.But,the warming of the warmest month may be a thermal stress on the development of coral reef.It reaches the upper limits of coral reef development,and leads the coral reef bleaching.Mankind activities,including wide scale building,oil gas factory near the island,traveling,fishing and breeding,may be also the potential stresses on limiting the coral reef development.The combination of summer warming and mankind stress is possibly to destroy the coral reef ecosystem of Weizhou Island.Based on a detailed field investigation,the modern coral reef distribution map around Weizhou Island was described.
    Research advance in nitrogen metabolism of plant and its environmental regulation
    XU Zhenzhu, ZHOU Guangsheng
    2004, (3):  511-516. 
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    Nitrogen metabolism is not only one of the basic processes of plant physiology,but also one of the important parts of global chemical cycle.Plant nitrogen assimilation directly takes part in the synthesis and conversion of amino acid through the reduction of nitrate.During this stage,some key enzymes,e.g,nitrate reductase (NR),glutamine systhetase (GS),glutamate dehydrogenase (GDH),glutamine synthase (GOGAT),aspargine synthetase (AS),and aspartate aminotransferase (AspAT) participate these processes.The protein is assimilated in plant cell through amino acid,and becomes a part of plant organism through modifying,classifying,transporting and storing processes,etc.The nitrogen metabolism is associated with carbonic metabolism through key enzyme regulations and the conversion of products,which consists of basic life process.Among these amino acids in plant cell,glutamic acid (Glu),glutamine (Gln),aspartic acid (Asp) and asparagines (Asn),etc,play a key role,which regulates their conversion each other and their contents in the plant cell through regulating formation and activity of those key enzymes.Environmental factors also affect the conversion and recycle of the key amino acids through regulating gene expression of the key enzymes and their activities.Nitrate and light intensity positively regulate the gene transcription of NR,but ammonium ions and Glu,Gln do the negative way.Water deficit is a very serious constraint on N2 fixation rate and soybean (Glycine max Merr.) grain yield,in which,ureide accumulation and degradation under water deficit appear to be the key issues of feedback mechanism on nitrogen fixation.Water stress decreases NR activity,but increases proteinase activity,and thus,they regulate plant nitrogen metabolism,although there are some different effects among species and cultivars.Water stress also decreases plant tissue protein content,ratio of protein and amino acid,and reduces the absorption of amino acid by plant.On the contrary,soil flooding decreases the content and accumulation amount of root nitrogen in winter wheat by 11.9% from booting to flowering stages and 39.1% during grain filling stage,and reduces the ratio of carbon and nitrogen by 79.6%.The results misadjust the metabolism between carbon and nitrogen,and result in the end of the root growth.Elevated CO2 level could decrease plant leaf nitrogen content under well-watered condition,but almost maintain stable under water deficit condition.The radiation of UV-B significantly reduces the partitioning coefficient and synthetic rate of Rubisco,which significantly decreases the photosynthetic rate.This paper reviewed the pathway of plant nitrogen assimilation,characteristics of key enzymes and their regulating mechanisms with picturing the regulating mode of NR,and described the signal sensing and conduct of plant nitrogen metabolism and the formation,transportation,storage and degradation of plant cell protein with picturing the schedule of protein transport of membrane system in plant cell.Seven key tasks are emphasized in this paper in terms of the review on the effects and mechanisms of key ecological factors including water stress on plant nitrogen metabolism.They are:1) the absorption mechanism of plant based on different nitrogen sources and environmental regulations,2) the localization and compartmentalization of the key enzymes of nitrogen mechanism in plant cell,3) the gene and environmental regulating model and their relationships in various key enzymes of nitrogen metabolism,4) the function of main cell organs and their responses to environmental factors in nitrogen metabolism process,5) physiological and chemical mechanism of nitrogen and the relationship between the mechanism and protein formation during crop grain filling,6) improving gene structure of special species or cultivars using gene engineering methods to enhance the resistance to environmental factor stress and the efficiency of absorption and transportation of nitrogen,and 7) the mechanism of natural nitrogen cycle and its response to human activity disturbance.
    Grazing resistance of rangeland plants
    WANG Shiping
    2004, (3):  517-522. 
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    Grazing resistance is the relative ability of plants to survive and grow in grazed systems,which can be divided into avoidance and tolerance components,based on the general mechanisms conferring resistance.The studies of resistance and tolerance thresholds will explain the reasons and mechanisms of grazing succession of plant communities.The difference of species resistant and tolerant thresholds depends on their grazing resistance strategies.Although both mechanisms are known to occur,the predominant mechanism or relative combination of mechanisms remains unknown for most species combinations and plant communities.Recognition of grazing avoidance or tolerance as the predominant resistance strategy inducing species composition shifts has important implications for grassland and pasture management.
    A review on types and mechanisms of compensation effect of crops under water deficit
    ZHAO Liying, DENG Xiping, SHAN Lun
    2004, (3):  523-526. 
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    In arid and semi-arid regions,the fact that crops suffering water deficit is unavoidable.Many studies indicated that plants have an ability to compensate the adverse effect of drought when the drought is moderate.But,how the compensation effects take place,and what are the physiological and biochemical mechanisms? This paper summarized the types,mechanisms and conditions of compensation effect that crops have under water deficit.The compensation effect is classified into growth compensation,physiological and biochemical compensation,and metabolism and output compensation.The biochemical and molecular mechanisms were discussed in terms of osmotic adjustment and dehydrate protection,and the biological basis of compensation effect was also elucidated.Finally,the direction for further study is pointed out.
    Research advance in ecosystem service of urban green space
    LI Feng, WANG Rusong
    2004, (3):  527-531. 
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    In this paper,the concept and connotation of urban green space and ecosystem service were expatiated,and the research advance in ecosystem service of urban green space was reviewed.The studies of ecosystem service of urban green space in overseas were focused on improving the quality of urban environment,maintaining biodiversity,providing amenity values,and ecosystem management;while in China,they were focused on the structure and function of urban green space,green quantity and quality,green equivalent,indicator system evaluation,value assessment,and application of CITYgreen model.The shortages and prospects of the researches on ecosystem service of urban green space were put forward.
    Impacts of cage culture on marine environment
    XU Yongjian, QIAN Lumin
    2004, (3):  532-536. 
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    The increasing production of sea food mainly depends on the developing mari-culture.Cage culture is intensive-culture and affects enormously their ambient waters.During the past 20 years,cage culture expended very rapidly,and the marine environment of cage area was worsen.This article reviews the impacts of cage culture on the aquatic environment,using studies published in the last 20 years.The impacts are numerous,including water pollution,impact on the sediment,genetic pollution,chemical pollution,and their resulting impacts on biodiversity in coastal sea.We present that we should give priority to study on the aquaculture and environment capacity in cage areas,and through utilizing the integrated culture restore the deteriorated culture environment.
    Dynamics of indole alkaloids in wheat varieties with various resistance to wheat aphid Sitobion avenae
    CAI Qingnian, WANG Yu, ZHANG Qingwen, ZHOU Mingzang
    2004, (3):  537-539. 
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    UV spectrometry measurement on the indole alkaloids (IA) contents of seven wheat varieties (KOK1679,My295,Li,Han4564 and Yanda1817,resistant to S. avenae;Shaanximazha and Lovrin10,susceptible to S. avenae) showed that during tillering and stem elongation stages,KOK1679,My295 and Li had a higher IA content (>0.5 mg穏-1 FW);and during heading and anthesis stages,the penultimate leaves of all five resistant varieties contained higher IA (>0.5 mg穏-1 FW).The IA content was lower in the flag leaves of both resistant and susceptible varieties,but was significantly higher in the ears of resistant varieties (up to 0.645 mg穏-1 FW in KOK1679) than in those of susceptible ones.It was showed that the IA content in wheat's ear played an important role in the resistance to S.avenae.
    Quantitative analysis of landscape patterns at the juncture of Shaanxi,Shanxi and Inner Mongolia,based on remote sensing data—Taking Yulin sheet TM image as an example
    LI Tuansheng
    2004, (3):  540-542. 
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    Based on the TM image of Yulin sheet and with the help of ERDAS,ARC/INFO and ARC/VIEW software,the landscape of Yulin sheet was classified.Using the spatial pattern analysis software FRAGSTATS of the vector version,a set of landscape indices were calculated at three scale levels of patches,classes and landscape.The results showed that landscape pattern indices could be successfully used in characterizing the spatial pattern of the studied area.However,this study should be further extended to the landscape of the same area in other period to analyze its dynamic change.FRAGSTATS was a good software,but should be improved by adding some indices such as PD2 developed by us.