毒杂草型退化草地植被群落特征的研究

Study on Vegetation Community's Structure of Degraded Grassland of Noxious and Miscellaneous Grass Type

在以狼毒(StellerachamaejasmeL.)侵入为主要特征的退化草地上,按狼毒盖度将草地划分为5个类组:Ⅰ类组(狼毒分盖度0～19%)、Ⅱ类组(狼毒分盖度20%～39%)、Ⅲ类组(狼毒分盖度40%～59%)、Ⅳ类组(狼毒分盖度60%～79%)、Ⅴ类组(狼毒分盖度80%～95%)。对各类组天然草地退化过程中植被的组成、作用及植物群落的动态变化规律进行了研究,结果表明,以针茅和扁穗冰草为优势种的山地草原,植被群落具有相对的稳定性。但是由于放牧强度的加大,改变了群落中植物间竞争格局,狼毒凭借对不良环境的适应能力以及植物间的竞争能力,个体数量及其在群落中的作用加强。伴随着狼毒分盖度的增加,针茅和扁穗冰草的地上生物量、密度、盖度和重要值明显下降,狼毒的相对值呈上升趋势。草地植物群落的Shannon Wiener多样性指数和Pielou均匀度指数随狼毒生物量的增加呈现出由低到高,再到低的变化趋势,Simpson优势度指数则呈现出相反的变化趋势;植物群落主要种的优势地位发生了明显的变化,狼毒由伴生种成为优势种,天然草原退化成狼毒为优势种的植被类型。

On the degraded grassland of noxious and miscellaneous grass type, according to its different degree of the degradation and the distribution of the Stellera chamaejasme L., the main noxious grass on this grassland type, the grassland can be plotted to five types: type 1, with Stellera chamaejasme density range of 0～19%; type 2, with Stellera chamaejasme density range of 20%～39%; type 3, with Stellera chamaejasme density range of 40%～59%; type 4, with Stellera chamaejasme density range of 60%～79%; type 5, with Stellera chamaejasme density range of 80%～95%. After research on the vegetation's constitution and function and the degradation regulation of the five types, the result shows that on the mountain grassland with S. Krylovii Roshev and A. cristatum L. Gaertn as the main advantage grasses, vegetation structure has relative stability. But due to herds increasing, the competition among different kind plants changed. As a result, Stellera chamaejasme L., with its special competition ability, its numbers and effects increasing step by step in the vegetation community. During the processes of the Stellera chamaejasme L increasing, the output over the ground and the density of the eatable grass such as S. Krylovii Roshev and A. cristatum L. Gaertn decreased. Following with the increasing of the Stellera chamaejasme L, the variety index Shannon-Wiener and the equality index Pielou are all changed from low to high and then to low again, but the superiority index Simpson takes on a opposite trend. At last the advanced grass of the vegetation community has been changed. Stellera chamaejasme L. changed from minor to major. So the natural grassland has been degraded by the Stellera chamaejasme L. On the basis of the above research, we have also brought forward some countermeasures to resume and enhance the production of such degraded grassland.