放牧胁迫下沙质草地植被的受损过程

通过在科尔沁沙地为期5a的放牧试验，分析探讨了过牧条件下沙质草地植被的受损过程。试验结果表明，持续过牧下，植被严重受损。其基本过程是，随着植物茎叶被大量啃食，草地群落盖度、高度和地上现存生物量急剧下降，连续过牧5a已分别较禁牧区低82．1％、94．0％和97．9％。但草地的净初级生产力(现存生物量 家畜采食量)下降幅度较小，第5年仍为禁牧的49．5％，而其被家畜啃食的净牧草量与现存生物量的比值高达23：1，远远高于中牧和轻牧的1：1和0．3：1水平。过牧下，物种丰富度、植物多样性和均匀度也急剧下降。第5年分别为禁牧区的35．0％、29．8％和45．9％，家畜喜食的多年生和1年生植物被不喜食的1年生植物所取代，劣质牧草比例达到86％，草地生活型趋于简单。随着地上净初级生产力的下降，地下生物量也趋于下降．根层分布浅层化。在这一退化过程的后期，由于地面裸露，风沙活动强烈，植被退化进程加速，这和草甸草原植被放牧所引起的退化存在明显区别。轻牧和中牧对草地群落盖度、高度和现存生物量也有很大影响．但试验期内对草地物种丰富度和植物多样性尚未产生明显影响。

Study on damaged process of the vegetation under grazing stress in sandy grassland

To better understand grazing effects on sandy grassland in semiarid area, a five-years grazing experiment was carried out in Horqin Sandy Land, Inner Mongolia. Results showed that vegetation was seriously degraded by continued over-grazing(OG). The degraded process started from rapid decrease in vegetation coverage and height and aboveground standing biomass when most parts of stems and leaves were grazed. The vegetation coverage, height and aboveground standing biomass in OG were 82.1%, 94% and 97.9% lower...