克氏针茅草原植物群落特征与物种生态位对放牧强度的响应

Responses of Plant Community Characteristics and Population Niche to Grazing Intensity in Stipa krylovii Grassland

在内蒙古锡林郭勒盟北部地区,探索禁牧、轻度放牧(0.34羊单位/hm2)、中度放牧(0.69羊单位/hm2)和重度放牧(1.53羊单位/hm2)对克氏针茅群落特征和生态位的影响,结果表明:随着放牧强度的增加,群落中大针茅逐渐被克氏针茅替代,银灰旋花逐渐出现,植物高度、盖度、鲜重、枯落物重量显著降低(P<0.05);重牧草场的多年生草本植物物种数显著高于禁牧和轻牧草场(P<0.05),物种Margalef丰富度指数、Shannon-Wiener多样性指数也显著增加(P<0.05);轻牧草场的Simpson优势度指数显著低于其他放牧强度(P<0.05)。禁牧草场中的大针茅、轻牧草场中的糙隐子草、中牧和重牧草场中的克氏针茅生态位宽度最大。在各放牧强度草场中,物种生态位重叠值主要集中在0.3~0.8区间;与禁牧相比,放牧增加了生态位重叠值0.3~0.8区间的种对数比例,其所占总对数比例随放牧强度增加而增加。物种生态位宽度与生态位重叠值呈线性相关,因此,可根据物种生态位宽度与重叠值控制草场中适口性差的物种数,进而有助于提升草原生态系统的稳定性。

In the northern region of Xilingol League,Inner Mongolia,the effects of four grazing intensity(prohibition of grazing,light grazing at 0.34 sheep units/hm 2,moderate grazing at 0.69 sheep u nits/hm 2,and heavy grazing at 1.53 sheep units/hm 2)on the community characteristics and ecological niche of the Stipa krylovii community were investigated.The results showed that with increasing grazing intensity,Stipa krylovii gradually replaced Stipa grandis in the community,Convolvulus ammannii gradually appeared,and plant height,coverage,fresh weight,and litter weight significantly decreased(P<0.05).The Margalef richness index and Shannon-Wiener diversity index significantly increased(P<0.05),while the Simpson dominance index in light grazing grasslands was significantly lower than that in other grazing intensities(P<0.05).Stipa grandis in prohibition of grazing grasslands,Cleistogenes squarrosa in light grazing grasslands,and Stipa krylovii in moderate and heavy grazing grasslands had the largest ecological niche widths.In all grazing intensity grasslands,species ecological niche overlap values were mainly concentrated in the range of 0.3 to 0.8.Grazing increased the rate of species pairs with overlapping niches within the range of 0.3 to 0.8 compared to prohibition of grazing,and the proportion of total pairs increased with increasing grazing intensity.Ecological niche width and overlap values were linearly correlated.Therefore,the number of poorly adapted species in the grassland can be controlled based on ecological niche width and overlap values,which can help improve the stability of grassland ecological system.