The Small-scale Heterogeneity Analysis On Stipa Breviflora Desert Steppe Under Free Grazing Condition

This experiment was carried out in July of 2006 in the Stipa breviflora desert steppe. The totle experimental area was 126.73hm2 and was divided into 19 sites and 475 plots, the average area was 0.23hm2 per plot. The vegetation density, height, amount and soil nutrients were measured by using the"fixed sample lines"; the vegetation coverage and frequency were measured by using the"pinprick method". The main results were as follows:(1) Stipa breviflora, Artemisia frigida, Cleistogenes songorica, Convolvulus ammannii, Kochia prostrate and Allium polyrhizum were selected to analyze the cluster distribution using the index of superiority, because their frequency was almost 80%, and the biomass of these plants was 90% of all biomass. The distribution of the six plants showed a significant heterogeneity.(2) The soil pH value had heterogeneity in defferent plots and layers.(3) The correlation had defference between soil nutrients in deffetent areas. The soil organic matter had big spatial dependency with total N, and had significant active correlations with total P, available P and N, while had no correlations with total K and available K.(4) The vegetation height and aboveground biomass had significant active correlations with organic matter, total N and P, available N and P, while had no correlations with total K and available K.(5) The indices of vegetation and soil in low areas were higher than that in other areas. The small-scale heterogeneity was evident.