Stipa Breviflora Community Characteristics And Spatial Heterogeneity Of Grassland Under Different Grazing Systems

A dynamic monitoring of population characteristics under different rotational grazing time and grazing system of Stipa breviflora desert steppe ecosystem were investigated during 2006-2010, which record the height, coverage and the density of plant populations in order to calculate the critical value, forage in rotational grazing area under different utilization grazing time and different grazing system were cut on the ground, dried and weighed. In 2009 to 2010, selected for different treatments and representative sample, laid dynamic monitoring plots of plant height, coverage, density and other characteristics of community indicators of the number of detailed investigation by mechanical sampling of plant species within plots, then analyzed of plant interspecific relationship and niche among different treatments of the species area, and the main spatial heterogeneity of plant populations were studied simultaneously. Meanwhile the corresponding plots for 0~10cm soil samples were taken back to the laboratory for routine determination of soil nutrients to analyze spatial distribution of soil nutrients under different treatments plot which sort by DCA and the CCA end method to study the relationship among plant species, soil nutrients and plot treatments. The main results were as follows:1 Different time in rotational grazing area, The height of main plant populations in late grazing area were lower in early grazing area, the coverage and density of Stipa breviflora were greater; the coverage and density of Cleistogenes songorica was lower in late grazing area. While in different grazing systems, the coverage and density of Stipa breviflora were continuous grazing area> rotational grazing area> control area; which of Cleistogenes songorica for the nearly equal between control area and rotational grazing area and both of which larger than that in continuous grazing area, coverage and density of Allium polyrhizum showed that in the control area> rotational grazing areas> continuous grazing area.2 Different time in rotational grazing area, the community aboveground biomass showed mid-grazing area> late grazing area> early grazing area. In different grazing system, the community aboveground biomass was control area> rotational grazing area> continuous grazing area.3 Interspecific relationships appeared intricately in late grazing area whereas simple in early grazing area at different use of rotational grazing time. In different grazing systems, grazing can significantly strengthen the interspecific relationships, and rotational grazing was better able to show significant correlation between species. Species compatibility among Rotational grazing, continuous grazing and control area showed a positive correlation.4 Early grazing and late grazing were benefit for niche breadth of Stipa breviflora at different use of rotational grazing time, while mid-grazing was good for that of Cleistogenes songorica. In different grazing systems, the niche breadth of Stipa breviflora showed continuous grazing area> rotational grazing area> control area, which of Allium polyrhizum and Cleistogenes songorica appeared as rotational grazing area> continuous grazing area> control area. Niche overlap among the main plant populations and Convolvulus ammannii, Carex duriuscula, Allium tenuissimum and Salsola collina was large.5 At different use of rotational grazing time, three plant populations of spatial variability in mid-grazing caused by random factors was lower, but was higher on maximum plant populations spatial variability. In different grazing systems, the main spatial heterogeneity of plant populations was relatively small, influenced greater by structural factors. There were three major plant species in the distribution of the main plaque mounted in the same treatments.6 Different use of the time in rotational grazing areas, there was a large nugget on soil total nitrogen, available potassium and organic carbon in early grazing area, and was a large maximum spatial variability in late grazing area. In different grazing system, spatial variability of the total nitrogen and organic carbon caused by random factors was continuous grazing area> rotational grazing area> control area, which of soil available nitrogen, total potassium and available potassium showed a maximum degree of the control area> rotational grazing area > continuous grazing area. Soil nutrients mainly affected not by random factors but by structural factors, spatial heterogeneity was small while spatial autocorrelation was large.7 At different use of time in the rotational grazing areas, the main plant species in early and late grazing area closely related to the spatial distribution of soil nutrients. In different grazing systems, the relationship between the main plant species and soil nutrients was rotational grazing area>control area>continuous grazing area. The relationship between main plant species and soil nutrients was Allium polyrhizum>Cleistogenes songorica>Stipa breviflora. Rotational grazing conditions were more conducive to remain stable on spatial distribution than that of continuous grazing conditions.8 Mid-grazing was more reasonable at different use of the time under rotational grazing, and in different grazing systems, rotational grazing condition was more favorable to sustainable development on Stipa breviflora steppe.