多年封育对半干旱区草场植物多样性的影响

Effect of Plant Diversity After Years of Enclosure in Semi-arid Area Grassland

以宁夏盐池县人工封育区为研究对象,自2003年开始连续观测封育区内植被群落种类及各特征值,并对群落结构、重要值以及物种多样性进行了分析。结果表明:(1)封育改变了封育区内原有的群落组成,使得原有优势种(黑沙蒿Artemisia ordosica)地位逐渐降低,群落结构发生了明显的变化。(2)封育措施在刚开始时确实有利于封育区内植被的恢复,但是随着封育的进行,植被恢复的速度逐渐减慢,在封育5a后封育区内植被盖度和生物量都逐渐降低,说明植被出现退化的现象,这表明封育时间与植被恢复并不是简单的线性关系,长时间的完全封育并不利于封育草场植被的恢复,合理的封育也应该是这时对封育区进行适当的人为干预,如进行刈割或者季节性的放牧等。(3)研究显示,各个物种多样性指数随封育时间处于一种周期性波动状态,封育区Shannon-Wiener,Simpson多样性指数随封育年限波动规律与物种丰富度的变化基本一致,都表现为封育刚开始的几年逐渐降低,随着封育时间的增长,会比刚开始封育的几年有较大的提高,之后呈现一定的规律性波动,低峰和高峰出现的频率均约为4a/次。

We took artificial fencing area of Yanchi County in Ningxia as the research site. We had observed the community types and the characteristic value of vegetation enclosure region since 2003, and analyzed the community structure, the important value and the species diversity. The results showed that： （1） the fencing had changed the community composition in the enclosure area, the status of dominant species （Artemisia ordosica） had decreased gradually in this area, and the community structure had also changed; （2） fencing enclosure was beneficial for vegetation restoration at the beginning, but vegetation restoration speed slowed down gradually over the time, vegetation began to degenerate in the fifth years after enclosed. The vegeta- tion coverage and biomass gradually reduced, indicating that the fencing time and vegetation restoration were not a simple linear relationship, long time of the enclosure was not conducive to the recovery of vegetation in the enclosed grassland. We should take some appropriate and reasonable human intervention to the enclosure area in this time, such as cutting or seasonal grazing; （3） this study showed that the various diversity of species was in a cyclical fluctuation with fencing time, the changes of Shannon-Wiener and Simpson diversity index with years were basically same with species richness, they all performed that in the first few years of enclosure decreased with fencing time, but with the increase of time, they would be much higher than those at the beginning of the enclosure years, and then showed with some regular fluctuation, and the frequencies of low peak and peak were all about once every four years.