古尔班通古特沙漠不同类型生物结皮对草本植物多样性影响

Effects of biological soil crust type on herbaceous diversity in the Gurbantunggut Desert

选择古尔班通古特沙漠的北部(一号点)、中部(二号点)、南部(三号点)3个不同样点的裸沙和藻结皮、地衣结皮与苔藓结皮3种生物结皮类型,对比研究了草本植物多样性的差异性及其主要环境影响因素。结果表明:(1)不同生物结皮类型的土壤理化性质有明显差异,土壤有机质、全氮、全磷、全钾含量以及黏粒、粉粒和细沙的含量随生物结皮演替显著上升,而中沙和粗沙的含量呈显著下降趋势,在沙漠不同区域呈现明显的空间异质性,二号样点中裸沙和藻结皮的养分含量和pH明显低于一号点和三号点。(2)草本植物的物种丰富度和Shannon-Wiener指数随生物结皮发育呈明显上升趋势,草本植物的物种组成、群落结构在不同类型生物结皮和沙漠不同区域均具有显著差异。(3)在土壤理化特征中,有机质、速效P和全K含量,以及pH和粉粒含量是影响草本植物分布的关键因子。(4)不同类型生物结皮之间的微地形和种类组成差异、种子生物学特性以及生物结皮在不同尺度下的土壤环境异质性共同影响草本植物在生物结皮中的物种组成和丰度,最终导致草本植物群落结构在生物结皮中的演替变化。

As pioneer community and ecosystem engineers in desert ecosystems,biological soil crusts(BSCs)play critical roles in maintaining soil surface stability and improving ecosystem function in arid regions.BSCs affect the seed dispersal,germination,and survival of vascular plants.However,the effect of BSCs on herbaceous plant diversity in the Gurbantunggut Desert is still unknown.In this study,we investigated the factors influencing herbaceous plant diversity in bare sand and three BSC types(algae,lichen,and moss crusts)in northern,central,and southern regions of the Gurbantunggut Desert.We detected significant differences in soil physicochemical properties among BSC types.For example,soil organic matter,total N,total P,total K,clay,silt,and fine sand contents significantly increased with BSC development;however,sand and coarse sand contents declined significantly.Moreover,spatial heterogeneity was obvious among desert regions.The nutrient content and pH in bare sand and algal crusts at Site 2 were lower than those at Site 1 and Site 3.Herbaceous plant richness and Shannon-Wiener diversity increased with BSC succession.The species composition and community structure also varied significantly among BSC types and desert areas.Soil physicochemical properties,soil organic matter,available P,total K,pH,and silt were identified as key factors shaping the herbaceous plant community structure.The changes in microtopography and species composition in different BSC types,biological properties of seeds and soil,and environmental heterogeneity may all contribute to herbaceous plant species composition and abundance in BSCs,leading to herbaceous plant community succession.