若尔盖县不同退化程度草地植物群落特征及土壤理化性质

Community characteristics and soil physical and chemical properties under different degraded grassland in Zoige,Sichuan

为探究鼠害常发区不同退化程度高寒草地生态系统的植物群落物种多样性及土壤理化性质变化.本研究采用样方法对若尔盖县4种退化草地植物群落特征及土壤理化性状开展了调查研究.结果表明:地上生物量、植被平均高度、总覆盖度随草地退化程度加剧而降低(P<0.05);物种丰富度、物种多样性随退化程度的加剧呈现显著降低的趋势(P<0.05);轻度退化草地到极度退化草地植被主要组成分别是:矮生嵩草+垂穗披碱草+鹅绒委陵菜、矮生嵩草+垂穗披碱草+苔草、矮生嵩草+垂穗披碱草+苔草及鹅绒委陵采+矮生嵩草+密花香薷;总体上,毒杂草类、莎草类和禾本类的重要值之比约为3.8∶1.5∶1,且各功能群重要值之间差异性显著(P<0.05),禾本科等优良牧草比例随草地退化加剧逐渐退出优势种群,最终形成以毒杂草类和莎草类占优势的极度退化草地;随着退化程度加剧,土壤表层容重、紧实度均呈显著上升趋势(P<0.05),而土壤全氮、全磷和速效钾含量呈显著下降趋势(P<0.05);冗余分析(RDA)发现土壤理化性质与植物群落特征的存在极显著相关性,土壤容重与植被覆盖度、植被高度、多样性指数、均匀度指数、丰富度指数、辛普森指数和地上生物量呈显著负相关关系,土壤全氮、土壤全磷和土壤含水量与植被覆盖度、植被高度、多样性指数、均匀度指数、辛普森指数和地上生物量呈显著正相关关系.研究结果可为川西北退化草地科学有效的治理和恢复提供理论依据.

In recent years the grassland of Northwest Sichuan has been seriously degraded by both natural factors such as significant rodent damage and other factors.In order to explore the stability, species diversity and dynamic change of soil physical and chemical properties of grassland ecosystem with different degrees of degradation.We investigated and analyzed the plant community characteristics and soil physical properties of four degraded grasslands in ZoigeCounty by sampling method.The results showed that the aboveground biomass, average height of vegetation and coverage significantly decreased with the aggravation of grassland degradation(P<0.05).The vegetation types from mild degraded grassland to extremely degraded grassland were Kobresiahumilis+Elymus nutans+Potentillaanserina,Kobresiahumilis+Elymusnutans+Carex,Kobresiahumilis+Elymusnutans+Carex,and Potentillaanserina+Kobresiahumilis+ElsholtziadensaBenth. With the aggravation of grassland degradation, the proportion of Gramineae and other fine herbage gradually withdrew from the dominant population, and finally formed the extremely degraded grassland vegetation type dominated by poisonous weeds and sedges.In addition, with the aggravation of soil degradation, the bulk density and compactness of soil surface increased significantly(P<0.05),while the total nitrogen, total phosphorus and available potassium content of the soil showed a significantly degradation(P<0.05).Redundant Analysis(RDA) revealed a significant correlation between soil physical and chemical properties and plant community characteristics, soil bulk density was negatively correlated with vegetation coverage, vegetation height, diversity index, evenness index, Richness Index, Simpson Index and aboveground biomass, soil total nitrogen, soil total phosphorus and soil water content were positively correlated with vegetation coverage, vegetation height, diversity index, evenness index, Simpson Index and aboveground biomass.The results provide theoretical basis for scientific and effective management and restoration of degraded grassland in Northwest Sichuan.