To better recover and reestablish the degraded sandy communities,relationship between the soil and plant communities were studied on 4 different degraded sandy communities that are fixed sand land (potential desertification stage),semi-fixed sand land (light desertification stage),semi-shifting sand land (medium desertification stage) and shifting sand land (heavy desertification stage) in Horqin sandy land.The results shown that during grassland desertification process:(1) The species quantity declined significantly from 20 to 11 Moreover,there was a significant difference among the aboveground biomass s (F=29.107,n=360,P＜0.001),the coverage (F=42.569,n=120,P＜0.001) and the density (F=38.817,n=120,P＜0.001),meanwhile,the ground biomass and coverage reduced gradually,the decrease rage were 82％,78％ and 85％ respectively.(2) Herbaceous plants are the domain species,while its ratio was obviously decreased.Moreover,the species quantity of perennial herbs and shrubs were declined.Chenopodiaceae had a wide adaptability which kept at relatively stable level and its important value was increased gradually.Gramineae and Legume were experienced a sharp decrease,meanwhile,there was a relatively small number of Compositae which were migrate from semi-fixed to shifting sand land.(3) Shannon-Wiener index,Simpson index,evenness index and Margalef index suggested a decreasing trend.(4) The physical and chemical properties of the soil also degraded.Moreover,there were a significant reduction of total phosphorus,total nitrogen,available phosphorus,available nitrogen and organic matter content (P＜0.05) along with the intensification of desertification.And (5) there was a significant correlation between the soil and vegetation (P＜0.05) which indicates that the desertification process is the result of the synergetic degradation of soil and vegetation.%以科尔沁沙地4种不同退化程度沙地群落为研究对象,采用野外植物样方调查与室内土壤理化分析相结合的方法,系统分析了固定沙地(潜在沙漠化阶段)、半固定沙地(轻度沙漠化阶段)、半流动沙地(中度沙漠化阶段)和流动沙地(严重沙漠化阶段)4个群落的植被、土壤特征的变化以及土壤与植被之间的相互关系,为退化沙质草地群落地恢复与重建提供科学依据.结果表明,(1)草地沙漠化过程中,群落物种组成发生显著变化,物种数不断减少,从20下降到11.不同群落盖度(F=42.569,n=120,P＜0.001)、密度(F=38.817,n=120,P＜0.001)和地上生物量(F=29.017,n=120,P＜0.001)均存在显著差异,且下降趋势明显,下降幅度分别为82％、78％和85％.(2)草地沙漠化过程中,草本植物占据绝对优势,但其比例明显下降,多年生草本植物和灌木的物种数总体呈下降趋势.藜科植物具有广适性,数量相对稳定,重要值呈现上升趋势;禾本科和豆科植物种类和重要值都呈大幅下降趋势.菊科植物相对较少,从半固定沙地到流动沙地,差巴嘎蒿(Artemisia halodendron)在群落中占有重要地位.(3)草地沙漠化过程中,Shannon-Wiener指数、Simpson指数、均匀度指数和Margalef指数均呈下降态势.(4)草地沙漠化过程中,土壤机械组成从固定沙地到流动沙地,粗砂含量增加,细砂粒、黏粉粒含量呈下降态势,土壤水分也不断减少.土壤养分全磷、全氮、速效磷、速效氮和有机质的含量随着沙漠化程度的加剧,表现出不同程度的降低,且差异显著(P＜0.05).(5)草地沙漠化过程中,土壤与植被间呈现出显著的相关性(P＜0.05),说明土壤与植被紧密联系在一起,沙漠化过程实质就是土壤与植被协同退化的结果.
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