# Drivers of Shrub Community Assembly in Semi-Arid Ecosystems: Integrated Evidence from Environmental Stress on the Western Loess Plateau

## TL;DR

This study explores how shrub communities in the western Loess Plateau respond to environmental stress and how these responses affect their diversity and assembly.

## Contribution

The study reveals that shrub community assembly is primarily deterministic and influenced by environmental stress gradients.

## Key findings

- Mean annual temperature is the main factor shaping shrub diversity due to habitat filtering.
- Shrub community assembly is dominated by deterministic processes across different stress gradients.
- Diversity and assembly patterns vary among shrubland types along environmental stress gradients.

## Abstract

Shrubland is the main vegetation on the western Loess Plateau, which has harsh environment conditions. Under stress environments, such as low temperature, human disturbance, and drought, the diversity levels and coexistence mechanisms of different types of shrub communities are different. It is necessary to clarify how the diversity and community assembly processes of the shrublands change in this area along these stress habitat gradients in order to understand their response mechanisms to stress conditions. Low temperature is a limiting factor affecting the diversity of shrub communities in this area. Different shrubland types are all driven by deterministic community assembly processes, even though the environmental driving forces may vary. This study provides insights into the vegetation restoration and stability processes in fragile habitat areas.

Shrub communities play an irreplaceable role in maintaining ecological security in the stressed habitat areas of Northwest China. In these areas, multiple types of shrublands coexist simultaneously. Their diversity levels and community assembly processes may perform different patterns along different stress gradients. This study using linear model fitting, principal component analysis, analyzed the species and phylogenetic diversity of desert, alpine, and secondary shrublands along the gradients of environmental stress factors such as topography, soil, and climate, which reflect low temperature, human disturbance, and drought stress habitats. The changing trend of the phylogenetic structure of different types of shrublands was also studied with using variance decomposition, and phylogenetic structure analysis, which reveals their diversity maintenance mechanisms along environmental stress gradients. The research shows that (1) the mean annual temperature is the main environmental factor shaping the diversity patterns and maintenance processes of shrub communities because low temperatures may lead to habitat filtering; (2) in the western Loess Plateau, the community assembly of different types of shrublands is dominated by deterministic processes, but the diversity and assembly patterns of different shrublands are inconsistent across different environmental stress gradients. Systematic research on the diversity characteristics and assembly patterns of different shrub communities is of great significance for clarifying the restoration, succession, and stability of stressed habitat areas.