Effect of long-term seasonal grazing of yak (Bos grunniens ) on botanical diversity of Potentilla fruticosa alpine rangeland in Qing-Zang Plateau

摘要

The effect of long-term (> 20 years) seasonal grazing of yak (Bos grunniens) on botanical diversity of Potentilla fruticosa alpine rangeland was investigated in the Qing-Zang Plateau. Thirty seven species (Gramineae: Cyperaceae: forbs: shrubs = 6 : 5 : 23 : 3) appeared in the paddock grazed in warm seasons (WSP), and 44 (Gramineae : Cyperaceae : forbs : shrubs = 7 : 6 : 27 : 4) in that grazed in cool seasons (CSP). Values for Richness Index. Shannon-Wiener and Simpson Diversity Indices and Pielou Richness Index were lower in WSP than in CSP. Vegetation coverage and community height were lower in WSP than in CSP (P < 0.01). Number of plant species was significantly smaller in WSP (7-16 species/m~2) than in CSP (17-22 species/m~2) (P < 0.001). Aboveground biomass of Gramineae was lower in WSP than in CSP (P < 0.01). Subdominant species in WSP were Kobresia humilis, Leontopodium nanum and Potentilla anserina which were short in height and grazing-resistant, while those in CSP were Poa pratensis . Elymus nutans and Kobresia capillifolia which were tall in height.