The Influence of Different Rotation Time to Spatial Heterogeneity of Vegetation in Desert Steppe
Spatial heterogeneity refers to the inhomogeneity and complexity of the spatial distribution of variables,which comprehensively reflects the spatial fragmentation and gradient of variables.Spatial heterogeneity is one of the basic characteristics of grassland ecosystem.It is of great significance to study the effect of grazing disturbance on grassland spatial heterogeneity.Taking Ningxia desert grassland as the research object,on the basis of the four-paddock rotational grazing in the early stage,was used CK,YT and YG measurements made include the plant community characteristics,plant community,the spatial heterogeneity of four main populations.The main results showed:(1)the important value of different rotational grazing time on the main species of grassland did not change obviously.There was no significant difference in community coverage,density,height and biomass under each treatment.(2)the Pielou E and Simpson C index of each treatment were close,and the Margalef R and Shannon-Wiener H index of rotational grazing treatments were significantly higher than those of CK.(3)vegetation density was positively correlated with available nitrogen and negatively correlated with soil bulk density,while aboveground biomass was positively correlated with soil organic matter and available nitrogen.(4)the coverage of plant community and the density of vegetation under each treatment were strongly correlated with the spatial autocorrelation of biomass.(5)the spatial heterogeneity of coverage,density and biomass of the four main populations was different.On the whole,the spatial heterogeneity of YG was small.The difference of heterogeneity is not only related to the biological characteristics of plants,but also the difference of rotation grazing time is the main factor of different spatial heterogeneity of population.(6)there was no significant difference in Cp,EE and ADF among edible herbage,but the spatial characteristics of nutritional components of the four main plants were different under different treatments.The content of crude protein in Agropyron mongolicum and Stipa breviflora varied moderately under each treatment However,the crude protein of Lespedeza potaninii and polygala tenuifolia varied moderately in the closed plot.From the point of view of the spatial distribution of community and population,it is considered that YG is more reasonable.