民勤沙区主要植物群落退化特征及其演替趋势分析

优势种植物密度和优势种盖度以及全部植物密度和盖度在样方间均存在不同程度的差异,表明民勤的植物生长在受干旱荒漠环境影响的同时,局部小环境对植物的分布和生长有显著影响。沙蒿当年幼苗密度最大,但幼苗的成活率很低,群落的投影盖度越小,则当年幼苗密度越大;梭梭不能实现自然更新;沙拐枣的生态位宽度较大,各年龄小苗均存在,自然更新能力强。在民勤沙区人工梭梭林普遍退化,尤其在西沙窝一带,梭梭人工林退化更为严重,有被沙拐枣取代的趋势。由于梭梭群落均为人工林,群落内地表异质性较大,因此,草本植物种类较多。

Degeneration Characteristics and Degeneration Succession Trend of the Main Plant Communities in the Sandy Areas in Minqin County

Minqin County is a typical desertification region in China,and the desert vegetation in the county is seriously degenerated.There is a significant difference of density and coverage of the dominant plant species between different plots of the same community,and there are also the regeneration and succession of plants in their degeneration process.Moreover,there are the differences of density and coverage of the dominant plant species and all the plant species between different plots in varying degrees.These reveal that the distribution and growth of plants are strongly affected by local microenvironment while restricted universally by the arid desert environment.Density of the underyear seedlings of Artemisia arenaria is the highest,but the survival rate of the seedlings is very low,and the lower the projective coverage of the community is,the higher the density of the underyear seedlings is;Haloxylon ammodendron can not naturally regenerate;the niche breadth of Calligonum mongolicum is high,the seedlings with different ages can grow,and its natural regeneration capability is the highest.The artificial forests of Haloxylon ammodendron in the sandy areas in Minqin County are universally degenerated, especially in the Xishawo region,and there is a succession trend that the artificial forests of Haloxylon ammodendron are replaced by that of Calligonum mongolicum.Because all the forests of Haloxylon ammodendron are artificially planted,the surface heterogeneity in the community is high,and the species of annual herbaceous plant are more.