牦牛放牧强度对高寒草甸暖季草场植被的影响

Effects of yaks stocking pates on aboveground and belowgrou nd blomass in kobrecia parva alpine meadow

暖季草场 2年的放牧试验结果表明 :随着放牧强度的提高 ,优良牧草盖度降低 ,杂草盖度增加 ,而且优良牧草盖度的年度变化与放牧强度呈极显著负相关 ,杂草盖度的年度变化与放牧强度呈极显著正相关 ;经过 1年的放牧 ,不同放牧强度下植物群落发生了变化 ,进一步回归分析 ,相似性系数的年度变化与放牧强度呈极显著的负相关 ;地上生物量的变化基本呈“S”型变化 ,而且随着放牧强度的加重 ,地上生物量趋于减小 ,优良牧草的比例减少 ,杂草比例增加 ;优良牧草比例的年度变化与放牧强度呈极显著负相关 。

Stocking rates of yaks had obvious effects on aboveg ro und and belowground biomass in Kobrecia parva alpine meadow There was signific ant difference between biomass of grasses and sedges, total biomass and differen t stocking rates(P<0 05), and ratio of sedges and grasses decreased, ratio of palatable weeds and toxic weeds increased with the rise of stocking rates The yearly changes of biomass composition for desirable herbage were negatively cor related with stocking rates(P<0 01), and the yearly changes of biomass compos ition for weeds were positively correlated with stocking rates (P<0 01) The absolute growth ratio of aboveground biomass reached to the maximum in July in 1999, but in 1998, it reached to the maximum in cold-season pastureland in Au gust, and as for warm-season pastureland, it reached to the maximum for control and light grazing in July, in August for moderate and heavy grazing There was an obviously decreasing trend on the belowground biomass of every soil stratum with the increase of stocking rates Belowground biomass of 0～10cm,10～20cm an d 20～30cm amounted to 88 04～89 37%, 7 14～9 34% and 2 25～3 5% of 0～ 30cm total belowground biomass respectively in warm-season pastureland, and 88 01～91 14%, 5 44～8 04% and 3 42～3 94% in cold-season pastureland re spectively There were negative correlation relationships between aboveground b iomass, belowground biomass for different soil stratums and stocking rates, and their linear regression equation as follows: Y=a-bx (b>0)It was a positive correlation relationship between aboveground biomass and below ground biomass, and regression equation as follows: Y=a+bx (b>0)