Effect Of Grazinging On Community Characteristics And Changing Of Nutrient Contents In Deyeuxia Angustifolia Meadow

Sanjiang plain located in the northeast of Heilongjiang province, which is the famous concentrated distrbution area of natural grassland in china. The area of natural grassland in Sanjiang plain is1.54×106hm2, account for14.12%of the total area. Vegetation mainly includes the swamps, marshes meadow and Deyeuxia angustifolia Meadow is the most important, whose area is2.54×105hm2, account for16.53%of the natural grassland of Sanjiang plain..In recent years, people are increasing grazing in Deyeuxia angustifolia Meadow, whose ecological function has changed, which focuses on the low species diversity and grass yield. How to realize resources sustainable in Deyeuxia angustifolia Meadow and highest economic benefits have become the most concern problem.The purpose of this project is to observe community characteristics under different grazing intensity, discuss the relations between grazing intensity and species diversity, productivity, plant nutrients. We are expected to provide important theory basis to maintain stable community, reasonable utilization of natural grassland, promote the sustainable development of ecological husbandry economy in Heilongjiang province and gain maximum benefit.The research about effect of grazing intensity on community characteristics and diversities was conducted in Deyeuxia angustifolia meadow of Sanjiang plain. Compared to no grazing, light grazing, moderate grazing and heavy grazing were set. Results showed that:1. Grazing increased the amount of population, and most of them were Gramineae, Compositae, Rosaceae and Polygonaceae. The most optimum community species diversity and stability were obtained on moderate grazing intensity. With the increasing of grazing intensity, the ratio of annual plant in community showed increasing trend.2. Compared to no grazing, the coverage, height and density of all grazing plot are decreased. After grazing, the important value of community dominant species Deyeuxia angustifolia was decreased according to the increasing of grazing intensity. Grazing main reduces the important value of perennial plant and minor increase the important value of annual plant.3. Species richness and evenness of Deyeuxia angustifolia community were all increased under light and moderate grazing intensity. The highest community species diversity and community stability were showed under moderate grazing intensity, which is consistent to Intermediate Disturbance Hypothesis.4. Aboveground biomass declined with the increasing of grazing intensity.Equal-compensation was observed in the light grazing plots, while under-compensation was found in the moderate and heavy grazing plots.The maximum aboveground standing crop within the whole grazing season occurred at mid-July. With the increasing of grazing intensity, aboveground standing crop of the main dominant plant showed decreasing trend, which is consistent to the trend of community.5. The contents of CP, ADF decreased with the increasing of grazing intensity, but EE increased. The contents of Ca of grazing plots and no grazing plot were contrary at the beginning of grazing, at the same time the highest contents of Ca was obtained at light grazing plot.The contents of Ca of light grazing plots and heavy grazing plot were consistent to no grazing plot at the late of grazing. The contents of P increased at first then decreased, and maximum occurred at August.