Abstract:

Vegetation restoration is very important to improve local environments and achieve sustainable development in sandy lands of Sichuan northwest. In this study, after an investigation on 136 samples of 1 m*1 m,a comparative study on the spatial distribution pattern of different dominant populations in desertification grassland in northwest Sichuan was made by the tests of dispersion index (ID), cluster size index (IC), Green index (GI), mean crowding index (IMC) and patchiness index (IP). Besides, the correlation analysis was used to compare the relationship of several indexes. The results showed that the patterns of those dominant populations were all aggregated distribution, however, the aggregation intensity was different on the whole. There were less community types in the exposure sandy land. Dominant populations were kobresia species and clump intensity was largest in all sandy land. There were more dominant populations in the fixed sandy land, the biggest of clump intensity was Potentilla anserina population in all dominant populations, and the least of clump intensity was Ajania tenuifoliapopulation. Clump intensity difference was observed. The clump intensity difference of the dominant populations in semi fixed sand and shifting sandy land was insignificant. Correlation analysis showed that there was a significant positive correlation among ID, ICS, GI and IMC, with coefficient almost equal to 1. It concluded that the main factors affecting the spatial distribution pattern of dominant population changed biological characteristics to soil microhabitats with the change of sand land type. It is to provide a reference to vegetation restoration of different sand land types in the northwest of Sichuan.

Key words: Sichuan northwest, Desertification, Dominant population, Spatial distribution pattern

摘要：

针对研究区不同沙化类型优势种群的分布特征，设置了136个1 m*1 m的样方，采用扩散系数（ID），聚集度大小指数（ICS），Green指数（GI），聚集频度指数（ICF），平均拥挤度指数（IMC），缀块指数（IP）等指标，分析了优势种群的分布格局及其形成的原因，并用相关分析比较了几个指数间的关系。结果表明：4种沙化类型上的优势植物种群分布格局皆属于聚集分布，但他们的聚集强度总体上有一定的差异。露沙地上的优势种群为嵩草（Kobresia）类植物，聚集程度明显大于其余3种沙化类型；固定沙地上优势种群较多，聚集强度差异较大，鹅绒委陵菜（Potentilla anserina）种群的聚集强度最大，细叶亚菊（Ajania tenuifolia）种群聚集分布强度最低；半固定沙地和流动沙地优势种群的聚集强度差异较小；相关分析表明，ID、ICS、GI、IMC之间呈显著的正相关且相关系数几乎等于1。由此可以得出，随露沙地向流动沙地演替，影响优势种群空间分布格局的主要因素由物种生物学特性逐渐变为土壤微生境，这为川西北高寒区沙化土地植被恢复提供参考。

关键词: 川西北, 沙化, 优势种群, 空间分布格局