Table of Content

15 June 2002, Volume 13 Issue 6

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Minimum sampling area and species richness of riparian community in Erdaobaihe forested watershed

DAI Limin, WANG Qingchun, DENG Hongbing, CHEN Gao, WANG Qingli

2002, (6):  641-645. 

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Riparian zone is an important component of small forested watershed. Due to the integrate effects of stream water and edge effect, there are obvious difference in composition, structure, and distribution pattern between riparian community and non-riparian community. Community minimum sampling areas are also different. In this study, minimum sampling areas of riparian community in original broad-leaved and Korean pine forest in Changbai Mountain were studied by using species-area curve. At the same time, species richness of riparian community was discussed. The results showed that the minimum sampling areas of riparian plant community were smaller than those of the non-riparian community. According to the original broad-leaved and Korean pine forest in Changbai Mountain, the average community minimum sampling areas in riparian zone of three plots including 60%,80%,and 90% of community species were about 80 m²,180 m², and 320 m², respectively. And then, those of forest community were about 260 m², 380 m², and 480 m² correspondingly. The results also showed that the species richness of riparian community was higher than that of non-riparian community.

Effect of elevated atmospheric CO₂ concentrations on photosynthesis light response characteristics of three coniferous tree species seedlings

WANG Miao, HAO Zhanqing, JI Lanzhu, ZHOU Guangsheng

2002, (6):  646-650. 

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Potted seedlings of Pinus koraiensis,Picea koraiensis, and Larix olgensis, the dominant coniferous tree species in Changbai Mountain, were grown under elevated CO₂ concentration (700 μmol·mol^-1) and ambient CO₂ concentration (400 μmol·mol^-1) for two year, and their photosynthesis light response curves were determined with CI-301PS CO₂ gas analysis system under a series of light intensity from 0 to 2500 μmol·quanta·m^-2·s^-1. The comparison of dark respiration rate (DRR), maximum net photosynthetic rate (A_max), quantum use efficiency (QUE), light compensation point (LCP), light saturation point (LSP) and photo inhibition point (PP) for the seedlings of these coniferous tree species under different CO₂ concentration showed that Larix olgensis, which had better adaptation of photosynthesis to elevated CO₂ concentration, was heliophilous species. The shade-tole- rant species Picea koraiensis showed the least adaptation of photosynthesis to elevated CO₂ concentration. Furthermore, the relationship between photosynthetic physiological character of tree species and their succession status was also discussed in this paper.

Improvement and application of digitized measure on shelterbelt porosity

GUAN Wenbin, LI Chunping, LI Shifeng, FAN Zhiping, XIE Chunhua

2002, (6):  651-657. 

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Based on the lots of investigation on farmland shelterbelts,we used digital camera to take pictures of shelterbelt and apply CIASsoftware to improve "digital image processing" for determining shelterbelt porosity so as to tho-roughly analyze the rule of porosity in farmland shelterbelts. Compared with the old digital image processing,the improved method possesses high accuracy,and it is more economical and more convenient to apply. The relationship between porosity of shelterbelts (β) and relative clear bole height (x) can be expressed as β=0.672x^0.469(r=0.9851,r_0.01= 0.4073,0≤β≤1) in the leaf period; and β=1.0681x^0.4304(r=0.9763,r 001= 0.4073,0≤β≤1) in the defoliation period. β varies with the stand age (a),taking the form of parabola,which can be expressed as β=0.0009a²-0.0364a+0.6828(0≤β≤1). Porosity at cross-section of shelterbelt can be used as an auxiliary index to evaluate the structure of belts. The calculation method of shelterbelt porosity of mixed shelterbelt can be expressed as β=(β₁n₁+β₂n₂)/(n₁+n₂). Among the popular,willow and elm pure shelterbelts with same disposition,popular shelterbelt structure is the best,with β_PPP<β_SSS<β_UUU,while the triangle disposition is better than the rectangle one among the same tree species. UPPU and SPPSof mixed structure have the optimal effect in popular-willow-elm mixed shelterbelts.

Coupling relationship between plant communities' species diversity and soil factors in ecotone between desert and oasis in Fukang,Xinjiang

ZHANG Linjing, YUE Ming, GU Fengxue, ZHANG Yuandong, PAN Xiaoling, ZHAO Guifang

2002, (6):  658-662. 

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Regression analysis was used to study the relationship between four diversity indices and 19 soil factors at three different soil layers in ecotone between desert and oasis in Fukang,Xinjiang. The results indicated that soil pH,total salt content,soil organic matter,Cl^-,K⁺+Na⁺,Mg²⁺,total nitrogen,and available phosphorus were correlative to species diversity significantly (P<0.05). The relationships between pHand diversity and between organic matter and diversity were best fitted in form of binomial model,and it meant that the highest species diversity occurred in middle of the gradient. The relationships between diversity and other 6 indices were in form of negative linear regression,showing that the contents of total salt,Cl^-,K⁺+Na⁺,Mg²⁺ were greater,and the species diversity indices were smaller. And the regression of total nitrogen and available phosphorus with evenness were similar to the former,that is,with the contents of soil total nitrogen and available phosphorus increasing,evenness indices decline correspondingly. The results of regression analysis between amount of plants and soil moisture and salt showed that plant abundance was influenced by soil water and salt significantly (P<0.01).

Effect of elevated CO₂ concentration on carbohydrate and nitrogen contents in seedlings foliage of three tree species in Changbai Mountain

ZHOU Yumei, HAN Shijie, ZHANG Junhui, ZOU Chunjing, WANG Chenrui

2002, (6):  663-666. 

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The contents of sucrose, fructose, soluble total sugar, starch and total nitrogen were analyzed in seedlings of Pinus koraiensis, Pinus sylvestriformis and Fraxinus mandshurica grown for three growing seasons in open-top chambers in Changbai mountain under elevated CO₂ (700, 500 μmol·mol^-1)and ambient CO₂ (350 μmol·mol^-1) concentrations. The results showed that in the first two growing seasons the treatment of 700 μmol·mol^-1 CO₂ accumulated the contents of starch in Pinus sylvestriformis and Fraxinus mandshurica seedlings, while total nitrogen content significantly decreased in Pinus koraiensis seedlings under 700 and 500 μmol·mol^-1 CO₂. The content of starch increased and the content of total nitrogen decreased in Pinus koraiensis and Fraxinus mandshurica seedlings grown under 700,500 μmol·mol^-1 CO₂ at the first two weeks in the third growing season. The change of starch and total nitrogen in Fraxinus mandshurica at the eighth week was similar to the first and second week. There was no significant increase or decrease of Cand Ncontent in Pinus sylvestriformis at the third growing season. CO₂ concentration affected the forms of carbohydrate accumulation in foliage.

Effects of global warming on productivity and soil moisture in Taihang Mountain: A transplant study

YANG Yonghui, WANG Zhiping, Yasuo SAKURA, TANG Changyuan, Shizuo SHINDO

2002, (6):  667-671. 

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By transferring natural vegetation with soil from high elevation to low elevation,a 2℃ warmer condition was created. In each site,5 different precipitation treatments were applied to test if the temperature and precipitation changes under global warming will result in a lower soil moisture condition and,therefore,feedback negatively on vegetation productivity of the Taihang Mountain. Two years' field experiment suggested that,because of the low adaptability of Arundinelia hirta under a warmer condition,its productivity decreased significantly at the end of the experiment. Productivities of grass with better adaptability such as Themeda japonica and Artemisia sacrorum did not change significantly between the two sites. Tested vegetation demonstrated a significant increase in productivity under the higher precipitation condition by showing 22% increase in productivity under 20% higher precipitation treatment. Soil moisture condition under treatments with higher precipitation was generally higher than that under treatments with lower precipitation. In the warmer site,soil moisture became higher since the beginning of the second year.

Temporal and spatial change characteristics of soil elements in reclaimed slope forestland

ZHANG Cheng'e, ZHENG Fenli

2002, (6):  672-674. 

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Calcium,Magnesium,Copper,Zinc,Manganese and Iron are necessary elements for plant growth and important indicators for soil quality evaluation. After forestland being reclaimed,spatial distributions of soil elements would be affected by plowing,erosion-deposition-transportation,and soil element properties. In the initial stage of forestland being reclaimed (the first and second year),Cu,Zn,Mn,Fe,K,Ca,and Mg in different slope locations would be increased. After two years,these elements would be decreased because of soil erosion. After six years,Cu,Fe,K,and Mg would be decreased by 1.5～4.56%.SiO₂ content on the upper slope would be increased as reclaimed year increased,but on the middle slope,SiO₂ content would be decreased and Al element would be increased.

Soil catalase activity of main plant communities in Leymus chinensis grassland in northeast China

LU Ping, GUO Jixun, ZHU Li

2002, (6):  675-679. 

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The seasonal dynamics of soil catalase activity of three different plants communities in Leymus chinensis grassland in northeast China were in a parabolas shape. The seasonal variation of Chloris virgata community was greater than those of Leymus chinensis community and Puccinellia tenuiflora community, and "seed effect" might be the main reason. The correlation between the activity of soil catalase in different soil layers and environmental factors were analyzed. The results showed that the activity of soil catalase was decreased gradually with depth of soil layer. The activity of soil catalase was closely correlated with rainfall and air temperature, and it was affected by soil temperature, soil moisture, and their interactions. The correlation between the activity and aboveground vegetation was very significant, and the growing condition of plant communities could be reflected by the activity of soil catalase.

Geographic variation in female reproductive characteristics and egg incubation of Eumeces chinensis

JI Xiang, HUANG Hongying, HU Xiaozhong, DU Weiguo

2002, (6):  680-684. 

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Geographic variation in female reproductive characteristics and egg incubation of Chinese skink (Eumeces chinensis) was studied by using two populations from eastern (Lishui,Zhejiang) and southern (Shaoguan, Guangdong) China, respectively. The results showed that female adults of the two populations both laid a single clutch per breeding season, and the clutch size, clutch mass, and egg mass had a positive correlation with female SVL. There was obvious geographic variation in head shape of females, reproductive characteristics, timing date of oviposition, and thermal dependence of egg incubation between two populations. Skinks from Shaoguan began to lay eggs in mid-May, approximately two weeks earlier than the timing date of skinks from Lishui. Skinks from Shaoguan produced more but smaller eggs. The size-specific (SVL) clutch size of skinks from Shaoguan outnumbered that of skinks from Lishui by 2.8 eggs. It implied there was a trade-off between the number and the size of offspring between populations, because there was no difference in size-specific clutch mass among skinks from both populations, and skinks within a population could produce larger clutches without a concomitant reduction in egg mass. Overall, compared to eggs incubated under 32℃, eggs incubated under 24℃ could produce larger (SVL) and well-developed hatchlings with less unutilized yolks. Compared to eggs from Lishui incubated under the same temperature of 24℃ and 32℃, eggs from Shaoguan produced hatchlings with smaller body wet mass and carcass dry mass. Accordingly, there was geographic variation in suitable range of incubation temperatures, and eggs laid by skinks from Lishui could successfully incubate in a wider range of temperatures.

Seasonal fluctuation of plant biomass in land remained bare in Hailun experimental station

YU Yongqiang, YU Wantai, ZHANG Lu

2002, (6):  685-688. 

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Analysis of the above-and under-ground biomass of the land remained bare for seven years and twenty years and the farmland in Hailun experimental station showed that total biomass increased over the bare period. There was no significant difference in above-ground biomass between bare lands,while the root biomass showed obvious difference,indicating that total biomass was differed mainly from root biomass between bare lands. With longer bare period,the ecosystem had the stronger resistance to environmental stress and the more stability. Meanwhile,its root biomass turnover value was small,which suggesting the higher ability to supply nutrient and energy stably.

Canopy spectral characteristics of different rice varieties

YANG Changming, YANG Linzhang, WEI Chao-ling, Ding Chaochen

2002, (6):  689-692. 

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By using spectroradiameter,canopy spectral characteristics such as reflection rate (α),absorption rate (τ),transmission rate (β),and extinction coefficient(K) of different rice varieties were analyzed and compared. The results showed the canopy spectral characteristics were significantly different among different rice varieties,especially under blue radiation (400～510 nm). In addition,these dissimilarities were more obvious in the late stage of growth period.

Fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors

ZHANG Yangzhu, LIAO Jipei, LI Fayun, HUANG Yunxiang, HU Ruizhi, YUAN Zhengping

2002, (6):  693-697. 

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By the method of Silva and Bremner,the fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors were studied. The results showed that the content of fixed ammonium in plough layer ranged from 141 mg·kg^-1 to 353 mg·kg^-1,averaged 272±67 mg·kg^-1,and accounted for 112% of total soil N. The content of fixed ammonium was in order of alluvial sandy soil > purple clayey soil > newly alluvial sandy soil > yellow clayey soil > reddish yellow clayey soil. There were four distribution models of fixed ammonium in the soil profiles: 1) fixed ammonium content increased with the increase of depth in the profiles; 2) fixed ammonium content decreased with the increase of depth; 3) there was no distinct change; and 4) abrupt increase or decrease was found in the profiles. The percentage of fixed ammonium to total Nin soils always increased with the increase of depth. The fixation of NH₄⁺ by soil was the strongest under 30℃. Long-term submergence benefited to the fixation of NH₄⁺ in newly alluvial sandy soil,purple clayey soil,and alluvial sandy soil,while the alternation of drying and wetting contributed to the fixation of NH₄⁺ in yellow clayey soil best. The content of fixed ammonium in tested soil was correlated with the content of clay <0.01 mm at the significant level,and not correlated with the content of clay <0.001 mm,total N,organic N,and matter.

Effects of ecological factors on infection process of Pyricularia grisea

DING Kejian, TAN Genjia, GAO Zhimou, JI Boheng

2002, (6):  698-700. 

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Rice blast is one of the main rice diseases. In order to discuss the occurrence regularity and improve the veracity of forecasting,the effects of ecological factors on infecting process,such as rice growth period,cultivar resistance,temperature,precipitation,and fertilization of nitrogen,were studied quantitatively. The results showed that adhering conidia on leaves,or ratio of infection was negatively correlative with the growth period of rice. The latent period of Pyricularia grisea was closely related to temperature,and within the range from 10℃ to 33℃,the latent period was the shortest at 28℃. The ratio of conidia adhering on leaves was also closely related to precipitation,especially the intensity and duration of precipitation in the first 5 hours after conidia contacting leaves,and there was no obvious effect after 5 hours. Under certain conditions,the ratio of expansive lesions to non-expansive lesions,the maximum area of expansive lesions,and variety resistance of rice were related to the rank of leaves.

Time-specific infection rate of Beauveria bassiana on Myzus persicae after topical inoculation of conidial suspension

XU Shoutao, FENG Mingguang, YING Shenghua

2002, (6):  701-704. 

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Conidial suspension(5×10⁶conidia·ml^-1) of the entomopathogenic fungus,Beauveria bassiana BBSG8702 was used to inoculate newly emerged apterous adults of the green peach aphid (Myzus persicae) on detached cabbage leaves in order to measure time-specific infection rate of the fungal agent. The aphids of conidia attached were disinfected using0.2% chlorothalonil solution at intervals of 8～56 h after inoculation and then maintained at 10 and 20℃ for daily observation. There was a significant difference (P<0.05) in mortality attributed to the fungal infection among the time intervals within56 h at 10℃ after inoculation or within40 h at 20℃.Compared with the control (not treated with 0.2% chlorothalonil after inoculation),time-specific infection rate at 10℃ was estimated as 22.9%,48.8%,64.9%,80.4%,72.7%,and 98.3% within8 h,16 h,24 h,32 h,40 h,and 56 h after inoculation, respectively. The same estimates at 20℃ were 31.6%,48.8%,58.6%,86.9%, 97.2%,and 98.7%, respectively. The results indicate that the first 24 h after inoculation was crucial to the infection of B. bassiana to M. persicae. Effective infection with the first 24 h accumulated to 59～65% at 10～20℃.

Structure and function of township agroecosystems and their correlation in northern plain areas of Zhejiang Province

WU Jianjun, KE Jinhu

2002, (6):  705-708. 

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The structure and functions of 15 township agroecosystems in northern plain areas of Zhejiang Province were investigated and studied. Both cluster analysis and correlation analysis were used to study the correlation between the holistic structure and function of the agroecosystems. The results showed that cluster analysis could reveal the correlation between the holistic structure and function of the agroecosystems, which was conducive for mastering the direction of holistic structural adjustment. Correlation analysis could identify the extent and direction of correlation between specific structural and functional indicators, which could serve as the basis for specific structural adjustment for optimization of functions.

Influence of environmental factors on the decomposition of organic carbon in agricultural soils

HUANG Yao, LIU Shiliang, SHEN Qirong, ZONG Lianggang

2002, (6):  709-714. 

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To quantitatively investigate the effects of environmental factors on organic carbon decomposition,CO₂-Cwas measured from the incubation of wheat and rice straw as well as their roots mixed with a paddy soil over a 90-day period. Results showed that decomposition of the straw carbon was faster than that of the roots. Amount of CO₂-Creleased from the organic matter decomposition was quantitatively related to its properties of C/Nratio. Increase of temperature within a lower temperature range enhanced greatly the decomposition while such an enhancement weakened within a higher temperature range. Under the moist condition,the temperature coefficient of organic carbon decomposition declined exponentially with the incubation time. The temperature coefficient did not significantly decrease with the time for the submerged condition after one-week incubation. The effect of water status showed that the decomposition at the water contents of 300g穔g^-1 and 500g穔g^-1 was faster than that under the treatments of 200g穔g^-1 and the submerged. Within the first month period of incubation,carbon amount released from the incubation of wheat straw was negatively related to the clay fraction of the soils.

Design and purification performance of vertical flow constructed wetland

WU Zhenbin, CHENG Shuiping, HE Feng, FU Guiping, JIN Jianming, CHEN Huirong

2002, (6):  715-718. 

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The technical design of small-scale plots (SSPs) of constructed wetland (CW) was described along with details of some associated wastewater purification effects in winter. Plots were comprised of two chambers. One chamber induced downward-flow,while the other created upward-flow. During Oct. 1997～Jan. 1998,the average plot removal rates for COD_Cr,BOD₅ and total suspended solids were 53.6%,78.7% and 80.2%,respectively. Reductions of bacteria,total coliforms (TC),fecal coliforms (FC) and algae were 99.4%,85.9%,89.7% and 97.7%,respectively. The mean removal rates of Kjeldahl nitrogen (KN),ammonium (NH₄⁺-N) and total phosphorus (TP) were 39.2%,16.5% and 25.8%. The treatment effects were not significantly different from each other. Concentrations of nitrate (NO₃^--N) in effluents were higher than those of the influent,and nitrate concentrations in the effluents of plant-systems were higher than those of the control. This indicated that presence of macrophytes enhanced nitrification in the CW. The downward followed by upward flow CWperformed better in removing contaminants and microorganisms from polluted surface water. It is an improved technology to purify water quality and rehabilitation of aquatic ecosystems.

Effects of constructed wetlands on treating with nitrogen and phosphorus in wastewater from hoggery

LIAO Xindi, LUO Shiming

2002, (6):  719-722. 

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Using plant species Vetiveria zizanioides (VCWS) and Cyperus alternifolius (CCWS) respectively,two constructed wetlands (CWS) with size of 1.0 m?0.5 m?0.8 m were established. The purifying function and its change pattern among different seasons,influent concentration and hydraulic retention time (HRT) of CWSon nitrogen and phosphorus in wastewater from a hoggery was studied throughout four seasons in the year. The results showed that the effects of HRTand wastewater concentration on the removal rate of NH₃-Nand S-PO₄^3- were obvious in both VCWSand CCWS. High removal rates of NH₃-Nand S-PO₄^3- were obtained in CCWSand VCWSin spring. Significant removal of TNin wastewater existed in CCWS and VCWS in autumn,while signi-ficant removal of TP in wastewater existed only in VCWS. The removal of TP or S-PO₄^3- against the HRT in CWS followed exponential function. The rates of Premoval in winter and summer changed with the influent concentrations. Under the same HRT,the change of S-PO₄^3- concentrations in outflow against the influent concentration followed a linear relationship.

Allelopathic effect of root exudates on pathogenic fungi of root rot in continuous cropping soybean

JU Huiyan, HAN Limei, WANG Shuqi, CONG Dengli

2002, (6):  723-727. 

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Allelopathic effect of root exudates on pathogenic fungi of root rot in continuous cropping soybean was studied by sand culture, water culture, and indoor culture experiments. The results showed that allelopathic promotion of root exudates on the growth of Fusarium semitectum, Gliocladium roseum and Fusarium oxysporum, especially Fusarium semitectum reached significant level or especially significant level in continuous cropping soybean compared with the control. Allelopathic promotion of root exudates on the growth of Fusarium semitectum and Gliocladium roseum in continuous cropping soybean was distinctly larger than that in rotation soybean, and the difference reached significant level under their low concentration. Allelopathic promotion of high concentration of root exudates on the growth of Fusarium semitectum was smaller than that of low concentration of root exudates, and the difference reached significant level in continuous cropping soybean. Allelopathic inhibition of high concentration of phthalic acid and propanedioic acid (L 5 and B 5) on the growth of Fusarium semitectum, Gliocladium roseum and Fusarium oxysporum, especially Fusarium semitectum reached significant level or especially significant level compared with the control. However, allelopathic promotion of low concentration of phthalic acid and propanedioic acid on the growth of Fusarium semitectum, Gliocladium roseum and Fusarium oxysporum partly reached significant level.

Preliminary study on anti-baculovirus mechanism of feeding housefly larvae (Musca domestia) and population infection model of outbreaking epidemic disease of shrimp (Panaeus chinensis)

WANG Wei, FENG Jiang, WANG Zhentang, SUN Gang, BAO Zhenmin

2002, (6):  728-730. 

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Based on indoors individual infection and outdoor population infection of shrimp, population infection model was established and anti-baculovirus mechanism of housefly larvae was analyzed. The results showed that 50% death time of the shrimps feeding with housefly larval reasonably was prolonged 3～5 times compared with the control group. Prophenoloxidase system of prawns was activited while feeding shrimps with housefly larval 7～10 days before infection by baculovirus, and prophenoloxidase activity was 3 times higher than the control group. The establishment of population infection model illustrated clearly important role of housefly larvae in improving the immunity of shrimps from baculovirus.

Variation of bacteria numbers in fish-shrimp mix-culturing ecosystem

LI Qiufen, CHEN Bijuan, QU Keming, YUAN Youxian, LI Jian, SUN Xiutao, ZHAO Fazhen

2002, (6):  731-734. 

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The study on variation of bacteria numbers in Penaeus chinensis-fish mix-culturing ecosystem in 1997. Indicated that at the beginning of culturing season,total number of heterotrophic bacteria and that of nitrate-reducing bacteria in mix-culturing ponds was low,but it was higher than that in mono-culturing shrimp pond. With time going on,the number of bacteria in mono-culturing pond increased rapidly and remained at a high level in August and September,an that in mix-culturing ponds also increased. But the latter increased slowly,and it was never over 10⁴ cells·ml^-1 and dropped in September. Number of bacteria in bottom of the ponds varied with the similar regulation,but the numbers was 10～100 times higher. The numbers of vibrio in mix-culturing ponds was always lower than that in contrastive pond at the same time. So,in fish-shrimp mix-culturing ponds,the contents of organic matter were lower and the total amount and variability of phytoplankton were higher than corresponding items in mono-culturing pond.It was concluded that mix-culture could stimulate and control the growth of heterotrophic bacteria,accelerate the degradation of organic pollutants,consequently fasten and stabilize the circulation of mater in ecosystem of ponds in culturing season.

Effect of stocking density on growth of juvenile Acipenser schrenckii

ZHUANG Ping, LI Dapeng, WANG Mingxue, ZHANG Zheng, ZHANG Longzhen, ZHANG Tao

2002, (6):  735-738. 

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The effect of stocking density on growth of juveniles Acipenser schrenckii was studied, and the results showed that juveniles Acipenser schrenckii reared for 28 days in a flowing water system under different stocking densities of 0.232,0.665,1.347,and 2.469 kg穖^-2 grew in allometry. There were no significant differences between the final and initial SVunder the four treatments. The growth efficiency,DWG,NY, and SGR of juveniles were decreased with the increase of stocking densities. However, the FCRand NYwere increased with the increase of stocking densities. There were significant differences between these parameters under the low and high densities treatment after 28 days. Moreover, there was a significant negative linear correlation between stocking density (D) and special growth rate (SGR).

Effect of salinity and body weight on the oxygen consumption of Oreochromis niloticus譕. mossambicus

LEI Sijia

2002, (6):  739-742. 

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The effects of salinity and body weight on oxygen consumption of Taiwan red tilapia (Oreochromis niloticus×O. mossambicus) were studied. The fish was divided into three groups by their body weight: 1.57～4.87 g (G₁),7.07～18.23 g (G₂) and 31.50～52.41 g (G₃). The results showed that oxygen consumption at diffe-rent salinities was significantly different (P<0.01). The rates of oxygen consumption in G₁ and G₂ were highest,with 0.41 mg O₂·g^-1·h^-1 for G₁,and 0.34 mg O₂·g^-1·h^-1 for G₂ respectively at salinity 7‰; while G₃ had highest level with 0.30 mg O₂·g^-1·h^-1 at 35‰. The lowest oxygen consumption level appeared at diffe-rent salinities with the different body weight. The lowest level in G₁,0.27 mg O₂·g^-1·h^-1,appeared at salinity 14‰. G₂ and G₃ had lowest oxygen consumption level at 21‰,with 0.22 mg O₂·g^-1·h^-1 and 0.13 mg O₂·g^-1·h^-1 respectively. ANOVshowed that oxygen consumption was significantly affected by the interaction of salinity and body weight.

Perspectives in researches on grassland ecology for the early21st century in China

LIANG Cunzhu, ZHU Tingcheng, WANG Deli, L? Xinlong

2002, (6):  743-746. 

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Grassland degeneration is a prominent problem in China. More in-depth studies should be carried out on the key problem-grassland degeneration for Chinese grassland ecologists in the early 21st century. Some hot research fields were restoration ecology,interface ecology,grazing ecology,health diagnoses and evaluation for grasslands. Among them,restoration ecology was the foundation for restoring degenerative grasslands; interface ecology involved with the point of contact for analyzing degenerative grasslands; grazing ecology was the effective way to control degenerative grasslands; diagnoses of grassland health benefited accurately appraising degenerative levels of grasslands; and evaluation for grassland was also considered as an estimation on services and benefits of grassland ecosystems.

Sustainable management for farmland shelterbelts

ZENG Dehui, JIANG Fengqi, FAN Zhiping

2002, (6):  747-749. 

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The spatio-temporal pattern of shelterbelt regeneration is an important issue which determinates whether shelterbelt network produces protective effects sustainably. This article developed a new method of imitating "normal forest" to manage shelterbelts. Based on an administrative village as an organized management unit, each shelterbelt in the organized management unit will be individually regenerated and regulated, until the number of the shelterbelts in each age-class from young to mature ones will be equal, and the shelterbelts in each age-class will be spatially distributed uniformly in the shelterbelt network of an organized management unit. Consequently, this method might temporally ensure sustainable and stable ecological services which are provided by the shelterbelts in an organized management unit.

Interaction between rare earths and nitrogen and phosphorus in soil-plant system

XU Xingkai, WANG Zijian, LIU Yan

2002, (6):  750-752. 

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Interaction between rare earths (REs) and nitrogen and phosphorus in soil-plant system is a hot spot in the research field of safety assessment for agricultural utilized rare earths. This interaction directly affects the productivity of arable soil,and is beneficial to assessing the response of rare earths to crop production and the eco-environmental safety. The interaction between rare earths and nitrogen and phosphorus in soil-plant system is briefly summarized,and it's put forward that the interaction between rare earths and nitrogen and phosphorus in the rhizophere of crop,surface layer of arable soil,and plant should be further investigated.

Complexity of land ecosystem

WU Cifang, CHEN Meiqiu

2002, (6):  753-756. 

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In recent years,complexity studies has become a new research region and been widely applied in engineering,bio-logy,economy,management,military,police and sociology. In this paper,from the view of complex science,the main complexity characteristics of land ecosystem were described,furthermore,the application of fractal,chaos,and artificial neural network on the complexity of land ecosystem were also discussed.

Current situation and prospect on the remediation of soils contaminated by heavy metals

LONG Xinxian, YANG Xiao'e, NI Wuzhong

2002, (6):  757-762. 

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Physio-chemical techniques and phytoremediation are the important methods for solving heavy metal pollution of evironment.According to the processes and mechanisms of reactions,physio-chemical techniques can be divided into chemical immobilization,soil washing and electrokinetic remediation,while phytoremediation includes phyto-stabilization,phyto-volatilization and phyto-extraction.The principles,advantages,disadvantages,feasibility and future research trends of the techniques were reviewed.

Assessing indices of container seedling quality

LU Min, JIANG Fengqi, SONG Xuan

2002, (6):  763-765. 

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In this paper,the assessing indices of container seedlings quality were synthesized in accordance with growth and physiological factors. The results showed that the seedling quality might be determined by the dormancy state of terminal bud,nutrient condition of plant,and the state of root system. The critical quality indices should include stem diameter at soil surface,dry weight of terminal bud,and soluble sugar content. Moreover,some indices such as root system vitality and dry weight of plant were also important.

Correlations of shoot and root growth and its role in screening for aluminum tolerance in wheat

LIN Xianyong, ZHANG Yongsong, LUO Ancheng

2002, (6):  766-768. 

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Alarge-volume solution culture and a small-pot soil test were adopted to screen for aluminum tolerance in wheat. Significant correlations were observed between root and shoot tolerance indices in wheat genotypes by using the same or different screening method. It was also shown that root tolerance parameters such as relative root length (RRL) and relative root dry weight (RRW) had more sensitive for differentiating aluminum tolerance in wheat genotypes indicated by higher standard deviation (SD),coefficient of variation (CV),and distrbution of data. Although shoot tolerance parameters,such as relative shoot length (RSL) and relative shoot dry weight (RSW) had less sensitive for differentiating aluminum tolerance within wheat genotypes indicated by lower SD,CV,and distribution of data,shoot growth parameters were reliable indicators of Al tolerance because they were sufficient to discriminate Al-tolerant and Al-sensitive genotypes in wheat. Shoot growth especially shoot length could be easily,rapidly,and non-destructively determined,and used effectively to screen for aluminum tolerance in a large-scale screening or breeding program.

Minimum sampling area and species richness of riparian community in Erdaobaihe forested watershed

DAI Limin, WANG Qingchun, DENG Hongbing, CHEN Gao, WANG Qingli

2002, (6):  641-645. 

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Riparian zone is an important component of small forested watershed. Due to the integrate effects of stream water and edge effect, there are obvious difference in composition, structure, and distribution pattern between riparian community and non-riparian community. Community minimum sampling areas are also different. In this study, minimum sampling areas of riparian community in original broad-leaved and Korean pine forest in Changbai Mountain were studied by using species-area curve. At the same time, species richness of riparian community was discussed. The results showed that the minimum sampling areas of riparian plant community were smaller than those of the non-riparian community. According to the original broad-leaved and Korean pine forest in Changbai Mountain, the average community minimum sampling areas in riparian zone of three plots including 60%,80%,and 90% of community species were about 80 m²,180 m², and 320 m², respectively. And then, those of forest community were about 260 m², 380 m², and 480 m² correspondingly. The results also showed that the species richness of riparian community was higher than that of non-riparian community.

Effect of elevated atmospheric CO₂ concentrations on photosynthesis light response characteristics of three coniferous tree species seedlings

WANG Miao, HAO Zhanqing, JI Lanzhu, ZHOU Guangsheng

2002, (6):  646-650. 

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Potted seedlings of Pinus koraiensis,Picea koraiensis, and Larix olgensis, the dominant coniferous tree species in Changbai Mountain, were grown under elevated CO₂ concentration (700 μmol·mol^-1) and ambient CO₂ concentration (400 μmol·mol^-1) for two year, and their photosynthesis light response curves were determined with CI-301PS CO₂ gas analysis system under a series of light intensity from 0 to 2500 μmol·quanta·m^-2·s^-1. The comparison of dark respiration rate (DRR), maximum net photosynthetic rate (A_max), quantum use efficiency (QUE), light compensation point (LCP), light saturation point (LSP) and photo inhibition point (PP) for the seedlings of these coniferous tree species under different CO₂ concentration showed that Larix olgensis, which had better adaptation of photosynthesis to elevated CO₂ concentration, was heliophilous species. The shade-tole- rant species Picea koraiensis showed the least adaptation of photosynthesis to elevated CO₂ concentration. Furthermore, the relationship between photosynthetic physiological character of tree species and their succession status was also discussed in this paper.

Improvement and application of digitized measure on shelterbelt porosity

GUAN Wenbin, LI Chunping, LI Shifeng, FAN Zhiping, XIE Chunhua

2002, (6):  651-657. 

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Based on the lots of investigation on farmland shelterbelts,we used digital camera to take pictures of shelterbelt and apply CIASsoftware to improve "digital image processing" for determining shelterbelt porosity so as to tho-roughly analyze the rule of porosity in farmland shelterbelts. Compared with the old digital image processing,the improved method possesses high accuracy,and it is more economical and more convenient to apply. The relationship between porosity of shelterbelts (β) and relative clear bole height (x) can be expressed as β=0.672x^0.469(r=0.9851,r_0.01= 0.4073,0≤β≤1) in the leaf period; and β=1.0681x^0.4304(r=0.9763,r 001= 0.4073,0≤β≤1) in the defoliation period. β varies with the stand age (a),taking the form of parabola,which can be expressed as β=0.0009a²-0.0364a+0.6828(0≤β≤1). Porosity at cross-section of shelterbelt can be used as an auxiliary index to evaluate the structure of belts. The calculation method of shelterbelt porosity of mixed shelterbelt can be expressed as β=(β₁n₁+β₂n₂)/(n₁+n₂). Among the popular,willow and elm pure shelterbelts with same disposition,popular shelterbelt structure is the best,with β_PPP<β_SSS<β_UUU,while the triangle disposition is better than the rectangle one among the same tree species. UPPU and SPPSof mixed structure have the optimal effect in popular-willow-elm mixed shelterbelts.

Coupling relationship between plant communities' species diversity and soil factors in ecotone between desert and oasis in Fukang,Xinjiang

ZHANG Linjing, YUE Ming, GU Fengxue, ZHANG Yuandong, PAN Xiaoling, ZHAO Guifang

2002, (6):  658-662. 

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Regression analysis was used to study the relationship between four diversity indices and 19 soil factors at three different soil layers in ecotone between desert and oasis in Fukang,Xinjiang. The results indicated that soil pH,total salt content,soil organic matter,Cl^-,K⁺+Na⁺,Mg²⁺,total nitrogen,and available phosphorus were correlative to species diversity significantly (P<0.05). The relationships between pHand diversity and between organic matter and diversity were best fitted in form of binomial model,and it meant that the highest species diversity occurred in middle of the gradient. The relationships between diversity and other 6 indices were in form of negative linear regression,showing that the contents of total salt,Cl^-,K⁺+Na⁺,Mg²⁺ were greater,and the species diversity indices were smaller. And the regression of total nitrogen and available phosphorus with evenness were similar to the former,that is,with the contents of soil total nitrogen and available phosphorus increasing,evenness indices decline correspondingly. The results of regression analysis between amount of plants and soil moisture and salt showed that plant abundance was influenced by soil water and salt significantly (P<0.01).

Effect of elevated CO₂ concentration on carbohydrate and nitrogen contents in seedlings foliage of three tree species in Changbai Mountain

ZHOU Yumei, HAN Shijie, ZHANG Junhui, ZOU Chunjing, WANG Chenrui

2002, (6):  663-666. 

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The contents of sucrose, fructose, soluble total sugar, starch and total nitrogen were analyzed in seedlings of Pinus koraiensis, Pinus sylvestriformis and Fraxinus mandshurica grown for three growing seasons in open-top chambers in Changbai mountain under elevated CO₂ (700, 500 μmol·mol^-1)and ambient CO₂ (350 μmol·mol^-1) concentrations. The results showed that in the first two growing seasons the treatment of 700 μmol·mol^-1 CO₂ accumulated the contents of starch in Pinus sylvestriformis and Fraxinus mandshurica seedlings, while total nitrogen content significantly decreased in Pinus koraiensis seedlings under 700 and 500 μmol·mol^-1 CO₂. The content of starch increased and the content of total nitrogen decreased in Pinus koraiensis and Fraxinus mandshurica seedlings grown under 700,500 μmol·mol^-1 CO₂ at the first two weeks in the third growing season. The change of starch and total nitrogen in Fraxinus mandshurica at the eighth week was similar to the first and second week. There was no significant increase or decrease of Cand Ncontent in Pinus sylvestriformis at the third growing season. CO₂ concentration affected the forms of carbohydrate accumulation in foliage.

Effects of global warming on productivity and soil moisture in Taihang Mountain: A transplant study

YANG Yonghui, WANG Zhiping, Yasuo SAKURA, TANG Changyuan, Shizuo SHINDO

2002, (6):  667-671. 

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By transferring natural vegetation with soil from high elevation to low elevation,a 2℃ warmer condition was created. In each site,5 different precipitation treatments were applied to test if the temperature and precipitation changes under global warming will result in a lower soil moisture condition and,therefore,feedback negatively on vegetation productivity of the Taihang Mountain. Two years' field experiment suggested that,because of the low adaptability of Arundinelia hirta under a warmer condition,its productivity decreased significantly at the end of the experiment. Productivities of grass with better adaptability such as Themeda japonica and Artemisia sacrorum did not change significantly between the two sites. Tested vegetation demonstrated a significant increase in productivity under the higher precipitation condition by showing 22% increase in productivity under 20% higher precipitation treatment. Soil moisture condition under treatments with higher precipitation was generally higher than that under treatments with lower precipitation. In the warmer site,soil moisture became higher since the beginning of the second year.

Temporal and spatial change characteristics of soil elements in reclaimed slope forestland

ZHANG Cheng'e, ZHENG Fenli

2002, (6):  672-674. 

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Calcium,Magnesium,Copper,Zinc,Manganese and Iron are necessary elements for plant growth and important indicators for soil quality evaluation. After forestland being reclaimed,spatial distributions of soil elements would be affected by plowing,erosion-deposition-transportation,and soil element properties. In the initial stage of forestland being reclaimed (the first and second year),Cu,Zn,Mn,Fe,K,Ca,and Mg in different slope locations would be increased. After two years,these elements would be decreased because of soil erosion. After six years,Cu,Fe,K,and Mg would be decreased by 1.5～4.56%.SiO₂ content on the upper slope would be increased as reclaimed year increased,but on the middle slope,SiO₂ content would be decreased and Al element would be increased.

Soil catalase activity of main plant communities in Leymus chinensis grassland in northeast China

LU Ping, GUO Jixun, ZHU Li

2002, (6):  675-679. 

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The seasonal dynamics of soil catalase activity of three different plants communities in Leymus chinensis grassland in northeast China were in a parabolas shape. The seasonal variation of Chloris virgata community was greater than those of Leymus chinensis community and Puccinellia tenuiflora community, and "seed effect" might be the main reason. The correlation between the activity of soil catalase in different soil layers and environmental factors were analyzed. The results showed that the activity of soil catalase was decreased gradually with depth of soil layer. The activity of soil catalase was closely correlated with rainfall and air temperature, and it was affected by soil temperature, soil moisture, and their interactions. The correlation between the activity and aboveground vegetation was very significant, and the growing condition of plant communities could be reflected by the activity of soil catalase.

Geographic variation in female reproductive characteristics and egg incubation of Eumeces chinensis

JI Xiang, HUANG Hongying, HU Xiaozhong, DU Weiguo

2002, (6):  680-684. 

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Geographic variation in female reproductive characteristics and egg incubation of Chinese skink (Eumeces chinensis) was studied by using two populations from eastern (Lishui,Zhejiang) and southern (Shaoguan, Guangdong) China, respectively. The results showed that female adults of the two populations both laid a single clutch per breeding season, and the clutch size, clutch mass, and egg mass had a positive correlation with female SVL. There was obvious geographic variation in head shape of females, reproductive characteristics, timing date of oviposition, and thermal dependence of egg incubation between two populations. Skinks from Shaoguan began to lay eggs in mid-May, approximately two weeks earlier than the timing date of skinks from Lishui. Skinks from Shaoguan produced more but smaller eggs. The size-specific (SVL) clutch size of skinks from Shaoguan outnumbered that of skinks from Lishui by 2.8 eggs. It implied there was a trade-off between the number and the size of offspring between populations, because there was no difference in size-specific clutch mass among skinks from both populations, and skinks within a population could produce larger clutches without a concomitant reduction in egg mass. Overall, compared to eggs incubated under 32℃, eggs incubated under 24℃ could produce larger (SVL) and well-developed hatchlings with less unutilized yolks. Compared to eggs from Lishui incubated under the same temperature of 24℃ and 32℃, eggs from Shaoguan produced hatchlings with smaller body wet mass and carcass dry mass. Accordingly, there was geographic variation in suitable range of incubation temperatures, and eggs laid by skinks from Lishui could successfully incubate in a wider range of temperatures.

Seasonal fluctuation of plant biomass in land remained bare in Hailun experimental station

YU Yongqiang, YU Wantai, ZHANG Lu

2002, (6):  685-688. 

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Analysis of the above-and under-ground biomass of the land remained bare for seven years and twenty years and the farmland in Hailun experimental station showed that total biomass increased over the bare period. There was no significant difference in above-ground biomass between bare lands,while the root biomass showed obvious difference,indicating that total biomass was differed mainly from root biomass between bare lands. With longer bare period,the ecosystem had the stronger resistance to environmental stress and the more stability. Meanwhile,its root biomass turnover value was small,which suggesting the higher ability to supply nutrient and energy stably.

Canopy spectral characteristics of different rice varieties

YANG Changming, YANG Linzhang, WEI Chao-ling, Ding Chaochen

2002, (6):  689-692. 

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By using spectroradiameter,canopy spectral characteristics such as reflection rate (α),absorption rate (τ),transmission rate (β),and extinction coefficient(K) of different rice varieties were analyzed and compared. The results showed the canopy spectral characteristics were significantly different among different rice varieties,especially under blue radiation (400～510 nm). In addition,these dissimilarities were more obvious in the late stage of growth period.

Fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors

ZHANG Yangzhu, LIAO Jipei, LI Fayun, HUANG Yunxiang, HU Ruizhi, YUAN Zhengping

2002, (6):  693-697. 

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By the method of Silva and Bremner,the fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors were studied. The results showed that the content of fixed ammonium in plough layer ranged from 141 mg·kg^-1 to 353 mg·kg^-1,averaged 272±67 mg·kg^-1,and accounted for 112% of total soil N. The content of fixed ammonium was in order of alluvial sandy soil > purple clayey soil > newly alluvial sandy soil > yellow clayey soil > reddish yellow clayey soil. There were four distribution models of fixed ammonium in the soil profiles: 1) fixed ammonium content increased with the increase of depth in the profiles; 2) fixed ammonium content decreased with the increase of depth; 3) there was no distinct change; and 4) abrupt increase or decrease was found in the profiles. The percentage of fixed ammonium to total Nin soils always increased with the increase of depth. The fixation of NH₄⁺ by soil was the strongest under 30℃. Long-term submergence benefited to the fixation of NH₄⁺ in newly alluvial sandy soil,purple clayey soil,and alluvial sandy soil,while the alternation of drying and wetting contributed to the fixation of NH₄⁺ in yellow clayey soil best. The content of fixed ammonium in tested soil was correlated with the content of clay <0.01 mm at the significant level,and not correlated with the content of clay <0.001 mm,total N,organic N,and matter.

Effects of ecological factors on infection process of Pyricularia grisea

DING Kejian, TAN Genjia, GAO Zhimou, JI Boheng

2002, (6):  698-700. 

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Rice blast is one of the main rice diseases. In order to discuss the occurrence regularity and improve the veracity of forecasting,the effects of ecological factors on infecting process,such as rice growth period,cultivar resistance,temperature,precipitation,and fertilization of nitrogen,were studied quantitatively. The results showed that adhering conidia on leaves,or ratio of infection was negatively correlative with the growth period of rice. The latent period of Pyricularia grisea was closely related to temperature,and within the range from 10℃ to 33℃,the latent period was the shortest at 28℃. The ratio of conidia adhering on leaves was also closely related to precipitation,especially the intensity and duration of precipitation in the first 5 hours after conidia contacting leaves,and there was no obvious effect after 5 hours. Under certain conditions,the ratio of expansive lesions to non-expansive lesions,the maximum area of expansive lesions,and variety resistance of rice were related to the rank of leaves.

Time-specific infection rate of Beauveria bassiana on Myzus persicae after topical inoculation of conidial suspension

XU Shoutao, FENG Mingguang, YING Shenghua

2002, (6):  701-704. 

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Conidial suspension(5×10⁶conidia·ml^-1) of the entomopathogenic fungus,Beauveria bassiana BBSG8702 was used to inoculate newly emerged apterous adults of the green peach aphid (Myzus persicae) on detached cabbage leaves in order to measure time-specific infection rate of the fungal agent. The aphids of conidia attached were disinfected using0.2% chlorothalonil solution at intervals of 8～56 h after inoculation and then maintained at 10 and 20℃ for daily observation. There was a significant difference (P<0.05) in mortality attributed to the fungal infection among the time intervals within56 h at 10℃ after inoculation or within40 h at 20℃.Compared with the control (not treated with 0.2% chlorothalonil after inoculation),time-specific infection rate at 10℃ was estimated as 22.9%,48.8%,64.9%,80.4%,72.7%,and 98.3% within8 h,16 h,24 h,32 h,40 h,and 56 h after inoculation, respectively. The same estimates at 20℃ were 31.6%,48.8%,58.6%,86.9%, 97.2%,and 98.7%, respectively. The results indicate that the first 24 h after inoculation was crucial to the infection of B. bassiana to M. persicae. Effective infection with the first 24 h accumulated to 59～65% at 10～20℃.

Structure and function of township agroecosystems and their correlation in northern plain areas of Zhejiang Province

WU Jianjun, KE Jinhu

2002, (6):  705-708. 

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The structure and functions of 15 township agroecosystems in northern plain areas of Zhejiang Province were investigated and studied. Both cluster analysis and correlation analysis were used to study the correlation between the holistic structure and function of the agroecosystems. The results showed that cluster analysis could reveal the correlation between the holistic structure and function of the agroecosystems, which was conducive for mastering the direction of holistic structural adjustment. Correlation analysis could identify the extent and direction of correlation between specific structural and functional indicators, which could serve as the basis for specific structural adjustment for optimization of functions.

Influence of environmental factors on the decomposition of organic carbon in agricultural soils

HUANG Yao, LIU Shiliang, SHEN Qirong, ZONG Lianggang

2002, (6):  709-714. 

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To quantitatively investigate the effects of environmental factors on organic carbon decomposition,CO₂-Cwas measured from the incubation of wheat and rice straw as well as their roots mixed with a paddy soil over a 90-day period. Results showed that decomposition of the straw carbon was faster than that of the roots. Amount of CO₂-Creleased from the organic matter decomposition was quantitatively related to its properties of C/Nratio. Increase of temperature within a lower temperature range enhanced greatly the decomposition while such an enhancement weakened within a higher temperature range. Under the moist condition,the temperature coefficient of organic carbon decomposition declined exponentially with the incubation time. The temperature coefficient did not significantly decrease with the time for the submerged condition after one-week incubation. The effect of water status showed that the decomposition at the water contents of 300g穔g^-1 and 500g穔g^-1 was faster than that under the treatments of 200g穔g^-1 and the submerged. Within the first month period of incubation,carbon amount released from the incubation of wheat straw was negatively related to the clay fraction of the soils.

Design and purification performance of vertical flow constructed wetland

WU Zhenbin, CHENG Shuiping, HE Feng, FU Guiping, JIN Jianming, CHEN Huirong

2002, (6):  715-718. 

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The technical design of small-scale plots (SSPs) of constructed wetland (CW) was described along with details of some associated wastewater purification effects in winter. Plots were comprised of two chambers. One chamber induced downward-flow,while the other created upward-flow. During Oct. 1997～Jan. 1998,the average plot removal rates for COD_Cr,BOD₅ and total suspended solids were 53.6%,78.7% and 80.2%,respectively. Reductions of bacteria,total coliforms (TC),fecal coliforms (FC) and algae were 99.4%,85.9%,89.7% and 97.7%,respectively. The mean removal rates of Kjeldahl nitrogen (KN),ammonium (NH₄⁺-N) and total phosphorus (TP) were 39.2%,16.5% and 25.8%. The treatment effects were not significantly different from each other. Concentrations of nitrate (NO₃^--N) in effluents were higher than those of the influent,and nitrate concentrations in the effluents of plant-systems were higher than those of the control. This indicated that presence of macrophytes enhanced nitrification in the CW. The downward followed by upward flow CWperformed better in removing contaminants and microorganisms from polluted surface water. It is an improved technology to purify water quality and rehabilitation of aquatic ecosystems.

Effects of constructed wetlands on treating with nitrogen and phosphorus in wastewater from hoggery

LIAO Xindi, LUO Shiming

2002, (6):  719-722. 

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Using plant species Vetiveria zizanioides (VCWS) and Cyperus alternifolius (CCWS) respectively,two constructed wetlands (CWS) with size of 1.0 m?0.5 m?0.8 m were established. The purifying function and its change pattern among different seasons,influent concentration and hydraulic retention time (HRT) of CWSon nitrogen and phosphorus in wastewater from a hoggery was studied throughout four seasons in the year. The results showed that the effects of HRTand wastewater concentration on the removal rate of NH₃-Nand S-PO₄^3- were obvious in both VCWSand CCWS. High removal rates of NH₃-Nand S-PO₄^3- were obtained in CCWSand VCWSin spring. Significant removal of TNin wastewater existed in CCWS and VCWS in autumn,while signi-ficant removal of TP in wastewater existed only in VCWS. The removal of TP or S-PO₄^3- against the HRT in CWS followed exponential function. The rates of Premoval in winter and summer changed with the influent concentrations. Under the same HRT,the change of S-PO₄^3- concentrations in outflow against the influent concentration followed a linear relationship.

Allelopathic effect of root exudates on pathogenic fungi of root rot in continuous cropping soybean

JU Huiyan, HAN Limei, WANG Shuqi, CONG Dengli

2002, (6):  723-727. 

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Allelopathic effect of root exudates on pathogenic fungi of root rot in continuous cropping soybean was studied by sand culture, water culture, and indoor culture experiments. The results showed that allelopathic promotion of root exudates on the growth of Fusarium semitectum, Gliocladium roseum and Fusarium oxysporum, especially Fusarium semitectum reached significant level or especially significant level in continuous cropping soybean compared with the control. Allelopathic promotion of root exudates on the growth of Fusarium semitectum and Gliocladium roseum in continuous cropping soybean was distinctly larger than that in rotation soybean, and the difference reached significant level under their low concentration. Allelopathic promotion of high concentration of root exudates on the growth of Fusarium semitectum was smaller than that of low concentration of root exudates, and the difference reached significant level in continuous cropping soybean. Allelopathic inhibition of high concentration of phthalic acid and propanedioic acid (L 5 and B 5) on the growth of Fusarium semitectum, Gliocladium roseum and Fusarium oxysporum, especially Fusarium semitectum reached significant level or especially significant level compared with the control. However, allelopathic promotion of low concentration of phthalic acid and propanedioic acid on the growth of Fusarium semitectum, Gliocladium roseum and Fusarium oxysporum partly reached significant level.

Preliminary study on anti-baculovirus mechanism of feeding housefly larvae (Musca domestia) and population infection model of outbreaking epidemic disease of shrimp (Panaeus chinensis)

WANG Wei, FENG Jiang, WANG Zhentang, SUN Gang, BAO Zhenmin

2002, (6):  728-730. 

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Based on indoors individual infection and outdoor population infection of shrimp, population infection model was established and anti-baculovirus mechanism of housefly larvae was analyzed. The results showed that 50% death time of the shrimps feeding with housefly larval reasonably was prolonged 3～5 times compared with the control group. Prophenoloxidase system of prawns was activited while feeding shrimps with housefly larval 7～10 days before infection by baculovirus, and prophenoloxidase activity was 3 times higher than the control group. The establishment of population infection model illustrated clearly important role of housefly larvae in improving the immunity of shrimps from baculovirus.

Variation of bacteria numbers in fish-shrimp mix-culturing ecosystem

LI Qiufen, CHEN Bijuan, QU Keming, YUAN Youxian, LI Jian, SUN Xiutao, ZHAO Fazhen

2002, (6):  731-734. 

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The study on variation of bacteria numbers in Penaeus chinensis-fish mix-culturing ecosystem in 1997. Indicated that at the beginning of culturing season,total number of heterotrophic bacteria and that of nitrate-reducing bacteria in mix-culturing ponds was low,but it was higher than that in mono-culturing shrimp pond. With time going on,the number of bacteria in mono-culturing pond increased rapidly and remained at a high level in August and September,an that in mix-culturing ponds also increased. But the latter increased slowly,and it was never over 10⁴ cells·ml^-1 and dropped in September. Number of bacteria in bottom of the ponds varied with the similar regulation,but the numbers was 10～100 times higher. The numbers of vibrio in mix-culturing ponds was always lower than that in contrastive pond at the same time. So,in fish-shrimp mix-culturing ponds,the contents of organic matter were lower and the total amount and variability of phytoplankton were higher than corresponding items in mono-culturing pond.It was concluded that mix-culture could stimulate and control the growth of heterotrophic bacteria,accelerate the degradation of organic pollutants,consequently fasten and stabilize the circulation of mater in ecosystem of ponds in culturing season.

Effect of stocking density on growth of juvenile Acipenser schrenckii

ZHUANG Ping, LI Dapeng, WANG Mingxue, ZHANG Zheng, ZHANG Longzhen, ZHANG Tao

2002, (6):  735-738. 

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The effect of stocking density on growth of juveniles Acipenser schrenckii was studied, and the results showed that juveniles Acipenser schrenckii reared for 28 days in a flowing water system under different stocking densities of 0.232,0.665,1.347,and 2.469 kg穖^-2 grew in allometry. There were no significant differences between the final and initial SVunder the four treatments. The growth efficiency,DWG,NY, and SGR of juveniles were decreased with the increase of stocking densities. However, the FCRand NYwere increased with the increase of stocking densities. There were significant differences between these parameters under the low and high densities treatment after 28 days. Moreover, there was a significant negative linear correlation between stocking density (D) and special growth rate (SGR).

Effect of salinity and body weight on the oxygen consumption of Oreochromis niloticus譕. mossambicus

LEI Sijia

2002, (6):  739-742. 

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The effects of salinity and body weight on oxygen consumption of Taiwan red tilapia (Oreochromis niloticus×O. mossambicus) were studied. The fish was divided into three groups by their body weight: 1.57～4.87 g (G₁),7.07～18.23 g (G₂) and 31.50～52.41 g (G₃). The results showed that oxygen consumption at diffe-rent salinities was significantly different (P<0.01). The rates of oxygen consumption in G₁ and G₂ were highest,with 0.41 mg O₂·g^-1·h^-1 for G₁,and 0.34 mg O₂·g^-1·h^-1 for G₂ respectively at salinity 7‰; while G₃ had highest level with 0.30 mg O₂·g^-1·h^-1 at 35‰. The lowest oxygen consumption level appeared at diffe-rent salinities with the different body weight. The lowest level in G₁,0.27 mg O₂·g^-1·h^-1,appeared at salinity 14‰. G₂ and G₃ had lowest oxygen consumption level at 21‰,with 0.22 mg O₂·g^-1·h^-1 and 0.13 mg O₂·g^-1·h^-1 respectively. ANOVshowed that oxygen consumption was significantly affected by the interaction of salinity and body weight.

Perspectives in researches on grassland ecology for the early21st century in China

LIANG Cunzhu, ZHU Tingcheng, WANG Deli, L? Xinlong

2002, (6):  743-746. 

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Grassland degeneration is a prominent problem in China. More in-depth studies should be carried out on the key problem-grassland degeneration for Chinese grassland ecologists in the early 21st century. Some hot research fields were restoration ecology,interface ecology,grazing ecology,health diagnoses and evaluation for grasslands. Among them,restoration ecology was the foundation for restoring degenerative grasslands; interface ecology involved with the point of contact for analyzing degenerative grasslands; grazing ecology was the effective way to control degenerative grasslands; diagnoses of grassland health benefited accurately appraising degenerative levels of grasslands; and evaluation for grassland was also considered as an estimation on services and benefits of grassland ecosystems.

Sustainable management for farmland shelterbelts

ZENG Dehui, JIANG Fengqi, FAN Zhiping

2002, (6):  747-749. 

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The spatio-temporal pattern of shelterbelt regeneration is an important issue which determinates whether shelterbelt network produces protective effects sustainably. This article developed a new method of imitating "normal forest" to manage shelterbelts. Based on an administrative village as an organized management unit, each shelterbelt in the organized management unit will be individually regenerated and regulated, until the number of the shelterbelts in each age-class from young to mature ones will be equal, and the shelterbelts in each age-class will be spatially distributed uniformly in the shelterbelt network of an organized management unit. Consequently, this method might temporally ensure sustainable and stable ecological services which are provided by the shelterbelts in an organized management unit.

Interaction between rare earths and nitrogen and phosphorus in soil-plant system

XU Xingkai, WANG Zijian, LIU Yan

2002, (6):  750-752. 

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Interaction between rare earths (REs) and nitrogen and phosphorus in soil-plant system is a hot spot in the research field of safety assessment for agricultural utilized rare earths. This interaction directly affects the productivity of arable soil,and is beneficial to assessing the response of rare earths to crop production and the eco-environmental safety. The interaction between rare earths and nitrogen and phosphorus in soil-plant system is briefly summarized,and it's put forward that the interaction between rare earths and nitrogen and phosphorus in the rhizophere of crop,surface layer of arable soil,and plant should be further investigated.

Complexity of land ecosystem

WU Cifang, CHEN Meiqiu

2002, (6):  753-756. 

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In recent years,complexity studies has become a new research region and been widely applied in engineering,bio-logy,economy,management,military,police and sociology. In this paper,from the view of complex science,the main complexity characteristics of land ecosystem were described,furthermore,the application of fractal,chaos,and artificial neural network on the complexity of land ecosystem were also discussed.

Current situation and prospect on the remediation of soils contaminated by heavy metals

LONG Xinxian, YANG Xiao'e, NI Wuzhong

2002, (6):  757-762. 

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Physio-chemical techniques and phytoremediation are the important methods for solving heavy metal pollution of evironment.According to the processes and mechanisms of reactions,physio-chemical techniques can be divided into chemical immobilization,soil washing and electrokinetic remediation,while phytoremediation includes phyto-stabilization,phyto-volatilization and phyto-extraction.The principles,advantages,disadvantages,feasibility and future research trends of the techniques were reviewed.

Assessing indices of container seedling quality

LU Min, JIANG Fengqi, SONG Xuan

2002, (6):  763-765. 

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In this paper,the assessing indices of container seedlings quality were synthesized in accordance with growth and physiological factors. The results showed that the seedling quality might be determined by the dormancy state of terminal bud,nutrient condition of plant,and the state of root system. The critical quality indices should include stem diameter at soil surface,dry weight of terminal bud,and soluble sugar content. Moreover,some indices such as root system vitality and dry weight of plant were also important.

Correlations of shoot and root growth and its role in screening for aluminum tolerance in wheat

LIN Xianyong, ZHANG Yongsong, LUO Ancheng

2002, (6):  766-768. 

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Alarge-volume solution culture and a small-pot soil test were adopted to screen for aluminum tolerance in wheat. Significant correlations were observed between root and shoot tolerance indices in wheat genotypes by using the same or different screening method. It was also shown that root tolerance parameters such as relative root length (RRL) and relative root dry weight (RRW) had more sensitive for differentiating aluminum tolerance in wheat genotypes indicated by higher standard deviation (SD),coefficient of variation (CV),and distrbution of data. Although shoot tolerance parameters,such as relative shoot length (RSL) and relative shoot dry weight (RSW) had less sensitive for differentiating aluminum tolerance within wheat genotypes indicated by lower SD,CV,and distribution of data,shoot growth parameters were reliable indicators of Al tolerance because they were sufficient to discriminate Al-tolerant and Al-sensitive genotypes in wheat. Shoot growth especially shoot length could be easily,rapidly,and non-destructively determined,and used effectively to screen for aluminum tolerance in a large-scale screening or breeding program.