陕北黄土区退耕还林地生物结皮分布及其影响因子研究

Distribution of biotic crusts and its influencing factors in the grain_for_green land of the loess region,northern Shaanxi Province.

为了科学评价黄土区退耕还林工程及其水土保持和生态效益,该文于2005年7—8月在陕西省延安市吴旗县进行了植被状况调查.通过对78个标准地的调查数据进行分析,结果表明:①干扰程度、坡向、坡度、地貌部位、植被结构、维管植物和微生境对生物结皮盖度具有明显影响.干扰程度弱,生物结皮盖度大,反之则小;阴坡生物结皮盖度大于阳坡;沟坡大于梁峁坡.②生物结皮盖度随着维管植物盖度和种数的增加而增加,但随着维管植物种数的进一步增加,生物结皮盖度反而下降.③植被结构不同,生物结皮盖度不同,草本植被结构大于乔灌草结构,乔灌草结构则大于灌草结构.

In order to scientifically evaluate the Grain-for-Green Project and its soil and water conservation benefit, as well as other ecological benefit in the loess region, August, 2005 in Wuqi County, Yah＇ an City, Shaanxi a vegetation investigation was conducted from July to Province. By analyzing the data from 78 sample plots, we obtained the distribution laws of biotic crusts in the grain-for-green land of the loess region, and achieved some influencing factors, including disturbance degree, aspect, topographic position, slope degree, vegetation structure, vascular plants and microhabitat. Results showed that： 1） coverage of biotic crusts on slopes with a low disturbance degree is larger than that with a high one, larger on north-facing slopes than that on south- facing ones, and larger on gully-slopes than that on ridge-slopes; 2） coverage of biotic crusts increases with the increase in coverage and species of vascular plants, but will decrease after a critical number of vascular plant species; and 3） coverage of biotic crusts in a herb-dominated vegetation structure is larger than that in a tree-dominated one, and that in a shrub-dominated one is the smallest.