[Fragmentation process of wetland landscape in watersheds of Sanjiang Plain, China].

The Sanjiang Plain is the largest fresh water wetland distribution area in China and the center of waterfowls breeding and habitat area in Asia, but over the past 50 years, more than 73% of its wetland had lost because of agricultural development, and as a result, the wetland biodiversity declines dramatically, and the remnant wetlands are in a very fragment state. Based on historical maps, remote sensing data and GIS techniques, this paper selected two watersheds to analyze their wetland landscape fragmentation process during 1950-2000. It was indicated that land reclamation resulted in a decrease of 98% wetland corridors in Qixing River, 90% in Naoli River, 87% in the middle reach of Bielahong River, and 94% in the lower reach of Bielahong River; The amount of isolated wetlands in watershed increased dramatically; The maximum patch areas of wetland decreased by 92.

[Adaptability of abnormal tadpole (Rana chensinensis) to water pH, salinity and alkalinity in Changbai Mountain of China].

Under field condition with 16-18 degree C water temperature, single-factor acute toxicity test was used to study the toxicity effects of water pH, salinity and carbonate-alkalinity on abnormal tadpole (R. chensinensis). The results showed that when the water salinity was 0.

The long-term nutrient accumulation with respect to anthropogenic impacts in the sediments from two freshwater marshes (Xianghai Wetlands, Northeast China).

Sediment cores, representing a range of watershed characteristics and anthropogenic impacts, were collected from two freshwater marshes at the Xianghai wetlands (Ramsar site no. 548) in order to trace the historical variation of nutrient accumulation. Cores were (210)Pb- and (137)Cs-dated, and these data were used to calculate sedimentation rates and sediment accumulation rates.

[Dynamics of CO2 and CH4 concentration in the mire soil and its impact factors].

The wetland plays a important role in global carbon cycling in terrestrial ecosystem, the greenhouse gas emission in the mire, especially the CO2 and CH4 level, show distinctly spatial and temporal variation. The product and emission of the CO2 and CH4 are related to soil organic carbon (SOC), dissolved organic carbon (DOC) and nitrogen content, meanwhile which are affected by the soil temperature and hydrological condition. The concentration of CO2 and CH4 are high in mire soil in the Sanjiang plain, especial at the root layer (10-35cm).

[The changes of the soil hydrothermal condition and the dynamics of C, N after the mire tillage].

The wetlands gain increasing attention to its crucial ecological and environmental function. The tillage of the mires in the Sanjiang Plain has played the important role in regulation of the region ecological balance and climate. Prior to tillage, the mean soil temperature of the topsoil (10 cm) in mire from June to September was 12.

[Conservation tillage systems in North America and their significance for China].

Soil degradation through erosion and desertification reduces soil productivity, and is a serious problem in agricultural production of China. To avert our arable land from further degradation, soil management must be shifted from degrading tillage to conservation practices. Over viewing the technology used in the 20th century for controlling soil degradation from erosion, conservation tillage developed in the United States and adopted in South America and Africa is one of the most successful measures to overcome soil degradation problems.

[Distribution and stock of mercury in typical wetland plant in the Sanjiang Plain].

Total mercury concentration of typical wetland plant was analyzed. There were great difference in mercury content among different plants, and the order was moss > alga > carex > herb > shrub. There was a trend of increasing total Hg concentrations from vascular plants to bryophytes, and from dry to wet site.

[Vertical distribution character of nutrient elements in peat of Sanjiang Plain].

Based on the methods of sampling in winter and dividing soil layer on the site, the vertical distribution character of normal amount nutrient elements N, P, Mg, Ca, Fe and nutrient trace elements Cu, Zn, Mn, B in peat of river bed-flood land and valley depression land in the Sanjiang Plain was studied systematically. The results showed that TN was accumulated in surface layer of peat, and TP was accumulated in root layer. The contents of TN and TP were decreased with the section depth increasing.

[Fate of fertilizer nitrogen in paddy field of black soil region].

Taking the N application rate, method and main varieties applied in paddy field of black soil in Northeast China as the parameters, a micro-plot tracer isotope trial and a normal urea plot trial were conducted for two years to study the fate of fertilizer nitrogen in paddy field. The results showed that 22.2%-46.

Long-term effects of fertilization on soil organic carbon changes in continuous corn of northeast China: RothC model simulations.

Soil organic C (SOC) content can increase by managing land use practices in which the rates of organic C input exceed those of organic C mineralization. Understanding the changes in SOC content of Black soils (mainly Typic Halpudoll) in northeast China is necessary for sustainable using of soil resources there. We used the RothC model to estimate SOC levels of Black soils under monoculture cropping corn in a long-term fertilization trial at Gongzhuling, Jilin Province, China.

[Ecological study on small-middle size soil animals in a compound ecosystem of farmland, grassland and woodland in the grassland region of Songnen Plain].

Based on the method of selecting samples in field, the ecological characters of small-middle size soil animals communities were investigated in a compound ecosystem of farmland, grassland and woodland in the grassland region of Songnen Plain. The results showed that the dominant groups were Hypogastruridae, Actinedida, Gamasida and Oribatida; and the common groups were Isotomidae and Jassidae. From the comparison analysis of farmland, grassland and woodland, the diversity of small-middle size soil animals communities was the highest in grassland, and the habitat in grassland was superior to the other two.

[Spatial distribution characteristics and ecological effects of carbon and nitrogen of soil in Huolin River catchment wetland].

This paper studied the spatial distribution characteristics and ecological effects of organic carbon and nitrogen in soils of Huolin River catchment wetland in horizontal and vertical levels. The results showed that the differences of horizontal and vertical distribution of organic carbon and nitrogen were very obvious, and of all the factors such as the period of wetting and drying cycles, leaching, plant and flood etc., the period of wetting and drying cycles was contents the critical one, which caused the differences.

[Landscape structure and ecological coupling analysis of ecotone on the west Sonnen Plain].

Ecotone is a special zone in the landscape, which is very susceptive to the changes in environmental conditions, and hence, is prone to the disturbance by unfavorable conditions. Human activity has a series of positive and negative effects on it, and greatly changes the geo-chemical process in the ecosystem. In the ecosystem, especially in the ecotone, different systems and regimes are interconnected and inter-determined.

[Distribution characteristics of metabolites of BHC and derivatives of DDT from the agricultural runoff in the western Songnen plain].

Through analyzing the contents of metabolites of BHC and derivatives of DDT in the runoff from paddy and corn land in the Western Songnen Plain, it was found that the contents of BHC and DDT were very lower and beta-BHC, which accounted for 73.5%-99.5% of the contents of BHC, was the main metabolite of BHC in the runoff.

[Characteristics of nitrogen distribution in peat deposit of freshwater marsh wetland].

Using the methods of sampling in winter and the dividing soil layers in soil profiles, the characteristics of TN, NH4(+)-N and NO3(-)-N concentration distribution in peat sediments of river bed-flood land and valley depression land in Sanjiang Plain where is the most extensive freshwater marsh wetland in China were systematically studied. The results showed that NH4(+)-N and NO3(-)-N was obviously accumulated in Asc layer, and TN content in Hil layer was the highest with the comparing to other layers. TN content in peat sediments was obviously increased with the peat particular size decreasing, NH4(+)-N was mainly distributed in peat component with 0.

[N2O concentration and its emission characteristics in Sanjiang plain wetland].

N2O concentration and its flux were measured in Sanjiang Plain wetland, from August to September in 2001, by using in situ closed chamber technique. The results showed that the mean N2O concentration above the ground was 281.7 x 10(-9) m3/m3, lower than the atmospheric N2O background, indicating the wetland maybe one of the important N2O sinks which scientists hadn't pay much attention to in the past.