禁牧对锡林郭勒典型草原物种多样性的影响

Effects of grazing-prohibition on species biodiversity of typical steppe in Xilinguole

为了研究禁牧对典型草原物种多样性的影响,对自由放牧和不同时间(1987、1997和2003年)禁牧的典型草原的物种组成进行了调查。结果表明:禁牧并未使典型草原的主要物种组成发生明显的改变,但使物种的相对重要性发生了明显变化,优势种的优势更加明显;同时,禁牧在一定的时间内可以提高典型草原的物种多样性,但随着禁牧时间的延长,典型草原的物种多样性和丰富度都表现出一种先上升后下降的趋势;在相同的禁牧或放牧条件下,水分条件较好的典型草原具有更高的物种多样性。可见,合理的禁牧时间与优越的水分条件有利于典型草原维持较高的物种多样性。典型草原物种多样性下降可能是人为干扰与干旱环境条件共同作用的结果。

In order to understand the effects of grazing-prohibition on the species diversity of typical steppe, the species composition of typical steppe in Xilinguole of Inner Mongolia was investi- gated under the conditions of free grazing and of grazing-prohibition since 1987, 1997, and 2003. The results showed that grazing-prohibition did not change the composition of dominant species markedly, but affected the relative importance of the species, with the dominance of dominant species increased. At the same time, grazing-prohibition enhanced the species diversity of the typical steppe in a definite period of time, but, as the period of grazing-prohibition extended, the species diversity and the richness of the typical steppe decreased. Moreover, under the same conditions of grazing or grazing-prohibition, the steppe with better water condition had higher spe- cies diversity. It was concluded that an appropriate duration of grazing-prohibition and favorable water condition was in favor of the maintenance of the species diversity of typical steppe, and the decline in species diversity of typical steppe in the region could be ascribed to the overgrazing and droughty environment condition.