干旱·半干旱地区生物结皮对植被演替的影响

摘要

干旱、半干旱地区土壤表层生物结皮的发育,改变了表层土壤的粗糙度和理化性质,其较高的持水性和对降水入渗的阻碍作用,改变了降水在土壤中的再分配过程,这不但影响土壤种子库中种子的组成和种子萌发,而且影响着上层植被的演替；生物结皮的形成和发育,使降水再分配过程浅层化,提高了浅层土壤水分的含量；而生物结皮对降水入渗的阻碍作用使深层土壤水分状况日益恶化,久之将导致区域内深根系植物的衰退,浅根系半灌木和草本植物得到发展,从而引起植被的演替.%The development of biological soil crusts on the topsoil in arid and semi-arid regions changed the roughness and physicochemical property of the topsoil.At the same time,the redistribution processes of precipitation was also changed because of biological soil crusts' higher water holding capacity and its impediment on the infiltration.These processes not only affect the seeds composition and seeds germination in the soil seeds bank,but also affect the vegetation succession.Shallow soil moisture is improved because biological soil crusts could hold more water in precipitations,but deep soil moisture gets worse and worse because infiltration is impeded by biological soil crusts,that would result in the recession of deep-rooted plants and the development of shallow-rooted semi-shrubs and herbaceous plants,which led to the vegetation succession in a long time.