内蒙古典型草原灌丛化对生物量和生物多样性的影响

通过样方调查，研究了内蒙古典型草原不同退化程度草地中小叶锦鸡儿 (Caragana microphylla Lam.)灌丛斑块空间分布格局、草地生物量及生物多样性特征。结果表明，从轻度到中度、重度退化草地，草本植物生物量呈减少趋势，小叶锦鸡儿生物量呈增加趋势，总生物量呈先减少后增加趋势；灌丛斑块生物多样性呈增加趋势，草地斑块生物多样性呈先减少后增加趋势，其中轻度退化草地中灌丛斑块生物多样性低于草地斑块，中度和重度退化草地中灌丛斑块生物多样性高于草地斑块。本研究认为，内蒙古典型草原灌丛化过程中，生态系统可能存在草本植物占优势或小叶锦鸡儿占优势这样两种稳定状态，这两种状态能维持较高生物量和生物多样性，而在由草本植物占优势向小叶锦鸡儿占优势转化的过渡阶段，系统不稳定，仅能维持较低生物量和生物多样性。

Effects of shrub encroachment on biomass and biodiversity in the typical steppe of Inner Mongolia

This study investigated spatial pattern, plant biomass and community characteristics of the shrub and interspace grass patches in Caragana microphylla Lam.(C. microphylla) encroached grassland of Inner Mongolia. Field quadrat surveys were conducted at three sites with lightly, moderately and seriously degradation states mainly resulting from overgrazing. Results indicated that the aboveground biomass of grass patches decreased with the increasing intensity of degradation, but C. microphylla showed reversed trend. The total aboveground biomass including grasses and C. microphylla decreased from the lightly to the moderately degradation sites and then increased from the moderately to the seriously degradation sites. Biodiversity increased at shrub patches with increasing degradation intensity from the lightly to the seriously degradation sites, but decreased from the lightly to the moderately degradation sites and then reversed from the moderately to the seriously degradation sites at the interspace grass patches. We noted that biodiversity of shrub patches was much less than that of the interspace grass patches at the lightly degradation site, while it was greater than the interspace grass patches at the moderately and seriously degradation sites. The above results suggest that two stable states might exist in the process of shrub encroachment, i.e., grasses dominated and C. microphylla dominated. Ecosystem was stable with more biodiversity and biomass when grasses or C. microphylla dominated, but it was unstable with less biodiversity and biomass at the transitional stage from grasses to shrubs.