Abiotic stress and human activities reduce plant diversity in desert riparian forests

Abstract

Plant diversity is very important for maintaining the structure and function of ecosystems. Affected by climate change, it is increasingly sensitive to abiotic stresses, especially in ecologically fragile arid areas. Moreover, human activities have accelerated this process, resulting in a reduction in plant diversity. Revealing the spatial pattern and effecting mechanisms of plant diversity at the watershed level is beneficial to biodiversity conservation. Here, we analyze changes in plant diversity and its influencing factors in the desert riparian forest in the lower reaches of the Kashgar River using niche theory, interspecific association analysis, geographic information system (GIS) mapping, redundancy analysis (RDA), and structural equation modelling (SEM). We show that the niche breadth of plants varies from 0.174 to 0.451, and niche overlap ranges from 0.059 to 0.995, and Populus euphratica and Tamarix chinensis are the dominant species for improving the desert environment and maintaining the stable and ecological balance of communities. Plant diversity has spatial heterogeneity that woody plants are higher than herbaceous plants, which decreases with increasing groundwater depth and salt content. Groundwater depth was the key factor to stress plant diversity. In fact, it works by influencing soil moisture and salt content. LULC change significantly reduced plant diversity (P < 0.05) and destroyed ecosystem balance. Plant diversity and NDVI were significantly positively correlated (P < 0.01). It is useful for understanding and predicting changes in plant diversity. Therefore, the effective implementation of ecological water conveyance can promote groundwater rise, alleviate soil water shortage, reduce salt content, and promote the increase in plant diversity. In addition, reasonable control of LULC changes and improvement of vegetation cover will help maintain higher plant diversity.