放牧对内蒙古乌拉山典型山地植物群落学特征的影响

Influence of Grazing on Plant Community Characteristics in Typical Mountainous Area in Wulashan,Inner Mongolia

对乌拉山不同放牧强度干扰下的山地典型植被的群落学特征进行了比较研究。根据乌拉山山地放牧时间频度及地上植被现状,分轻度放牧、中度放牧和重度放牧3个等级,另设未放牧(围封)样地进行对照分析。结果表明,不同强度放牧对草地群落生长量及多样性特征均有显著的影响。随着放牧强度的增加,群落总盖度、高生长、个体密度、生物量均呈下降趋势,中度和重度放牧后各项指标较围封样地差异极显著(P<0.01)。在中度放牧样地,草地物种相对丰富度指数、Shannon-Wiener多样性指数、Simpson优势度指数和Pielou均匀度指数均高于其他样地。中度和重度放牧后扁桃属灌丛密度和生物量下降极显著(P<0.01),重度放牧后其冠幅和高度较未放牧样地显著下降(P<0.05)。在天然油松林内重度放牧后,林下无灌木生存,油松天然更新均为当年种子萌发长出的1年生苗,密度为平均10 360株/hm^2;与此相反,围封区内油松林下灌木保存2 400丛/hm^2,1年生更新苗2 984株/hm^2,2~5年生苗木570株/hm^2,6~8年生255株/hm^2,分别占总数的78.4%、14.9%和6.7%;家畜采食是油松林更新受阻的主要原因。

The characteristics of plant community under different grazing intensities in Wulashan have been studied. According to the grazing time and frequency and the present situations of above - ground vegetations, there are three grades of light grazing, moderate grazing and heavy grazing, with the enclosed plot as check. The results show that there is significant influence of different grazing intensities on the growth of grassland community and diversity characters. And with the increase of grazing intensity, the total coverage of community, height, density and bio- mass have decreased, there are extremely differences of the indexes among the moderate and heavy grazing and the enclosed plot （ p 〈 O. O1 ）. In moderate grazing plot, the relative richness index, Shannon - wiener index, Simpson index and Pielou index are higher than the ones in other plots. The intensity and biomass of Amygdalus shrubs have dropped obviously in moderate and heavy grazing （ P 〈 0. 01 ）, and in heavy grazing plot the canopy and height of Amygdalus shrubs have dropped obviously than the ones in the enclosed plot （ P 〈 0. 05 ）. In natural forest of Pinus tabulaeformis, after heavy grazing, no shrubs can exist, the natural regeneration seedlings are one -year seedlings sprouted from the current seeds with the average density of 10 360 stocks/hm^2. On the contrary, in the enclosed plot, the average density of shrub, one - year regeneration seedling, 2 - 5 years seedling and 6 - 8 years seedling are 2 400 stocks/hm^2, 2 984 stocks/hm^2 , 570 stocks/hm^2 and 255 stocks/hm^2 , taking up 78.4% , 14. 9% and 6. 7% of the total numbers separately. Animal intake is the main factor for preventing the regeneration of Pinus tabulaeformis.