柴达木盆地优势物种分布及生物量分配的环境驱动模式分析

Environmental Drivers Shaping Dominant Species Distribution and Biomass Allocation Analysis in the Qaidam Basin

摘要:

荒漠生态系统中土壤养分含量低,气候严酷导致植物在环境胁迫下表现出独特的生理和生态特性,这是荒漠生态系统多样性和维持稳定的基础。然而,柴达木盆地土壤与植物生物量分配关系及其维持荒漠草原生态系统稳定性过程仍不清晰。本研究通过柴达木盆地内35个样地175个样方86种优势植物重排序、异速生长关系、方差分解及结构方程模型方式,分析研究区土壤粒径与植物物种多样性沿干旱梯度的分布特征,以及土壤养分与植物地上、地下生物量之间的关系及其影响。结果表明:(1)柴达木盆地35个样点物种丰富度具有明显的环境梯度特征,经过重排序分析呈多个物种集合。多年生优势物种地上生物量显著高于一年生植物(P<0.01),证明优势物种分布模式为集群分布,多年生灌木与半灌木植物的地上、地下生物量异速生长关系均不显著(P=0.885),而一年生优势物种地下生物量分配速率高于地上;(2)逐步回归法筛选出影响优势物种分布的7个气候因子,它们对研究区多年生灌木、半灌木植物地上生物量影响程度(方差分解地上生物量R²=0.318)高于对其地下生物量的影响(地下生物量R²=0.01),而海拔对其地上、地下生物量的影响不显著,结构方程模型证明海拔间接影响优势物种地上、地下生物量,表明柴达木盆地海拔变化引起水热协同变化,极端气候(如等温性、最冷季降雨与最湿月、最湿季降雨)对其存在显著正、负影响,土壤粒径对其无显著影响。

Abstract:

The low nutrient content of soil in desert ecosystems,combined with harsh climatic conditions,causes plants to develop unique physiological and ecological traits under environmental stress,forming the basis for the diversity and stability of desert ecosystems.However,the relationship between soil and plant biomass allocation in the Qaidam Basin and its role in maintaining desert grassland ecosystem stability remains unclear.This study analyzed the distribution characteristics of soil particle size and plant species diversity along the aridity gradient in 35 sampling sites with 175 quadrats and 86 dominant plant species in the Qaidam Basin,using methods such as plant species reordering,allometric growth relationships,variance decomposition,and structural equation modeling.It also investigated the relationship between soil nutrients and aboveground and belowground biomass of plants,and their effects on ecosystem stability.The results showed that:(1)Species richness across the 35 sites in the Qaidam Basin displays distinct environmental gradient characteristics.Perennial dominant species have significantly higher aboveground biomass compared to annual species(P<0.01),indicating that the allometric growth relationships between aboveground and belowground biomass of perennial shrubs and semishrubs are not significant(P=0.885),whereas annual dominant species allocate more biomass belowground than aboveground.(2)Stepwise regression identified seven climatic factors affecting the distribution of dominant species,and their influence on the aboveground biomass of perennial shrubs and semi-shrubs(variance decomposition R²=0.318 for aboveground biomass) was greater than their influence on belowground biomass(R²=0.01 for belowground biomass).Elevation had no significant direct effect on aboveground or belowground biomass,but the structural equation model demonstrated that elevation indirectly affects the biomass of dominant species.This indicates that altitudedriven changes in water and heat conditions,along with extreme climate events(such as isothermality,precipitation in the coldest season,and precipitation in the wettest month and season),have significant positive and negative impacts on biomass,while soil particle size has no significant effect.