The spatial distribution patterns of major populations in the
Achnatherum splendens communities inside and beyond fence limits
were comparatively studied by taking typical A.splendens grassland in Sanjiaocheng breeding sheep farm of Qinghai Province as the study subject,sampling by contiguous quadrat grid and making use of such indexes as variance/mean ration,negative binomial parameter,dispersion coefficient,Cassie index,clumping index,and patchiness index.The results showed that in the A.splendens communities inside fence limits all the dominant populations but Taraxacum dissectum population,which presented a random spatial distribution,had an aggregated spatial distribution;in the the A.splendens communities beyond fence limits,all the populations but Polygonum sibiricum population showed an aggregated distribution,the aggregation degree of the populations beyond fence limits was higher than that inside fence limits.This distribution pattern of the species is mainly related to their ecological and biological characters.