Economic spectrum of desert ephemeral plants along a precipitation gradient in the Gurbantungut desert: aboveground and belowground functional traits determine productivity

Precipitation is a pivotal factor regulating ecosystem patterns and processes in arid and semi-arid regions and plays a significant role in plant community development. This study aims to elucidate the variation patterns of above-ground and belowground functional traits in herbaceous plant communities along natural precipitation gradients, as well as the specific mechanisms through which shifts in community-weighted mean trait values influence productivity. Six sampling points were established along a precipitation gradient (115, 120, 125.8, 135, 137.5, and 160 mm) in the Gurbantunggut Desert. Species diversity, biomass, and leaf and root functional traits were measured to investigate their trends and interrelationships. Results indicate that increasing precipitation enhanced community cover and biomass, both of which exhibited rising trends, whereas community richness did not follow a similar pattern. Above- and belowground functional traits varied in accordance with the plant economic spectrum: under lowest precipitation, stands exhibited a high-turnover strategy characterized by high specific leaf area and specific root length; Under comparatively higher precipitation, a high-investment strategy prevailed, featuring larger individual size and thicker root diameter. Structural equation modeling (SEM) revealed that variations in herbaceous plant functional traits and soil total nitrogen content were the primary pathways influencing above- and belowground biomass. Specifically, specific leaf area (SLA) was negatively correlated with aboveground biomass, while belowground root diameter (RD) was positively correlated with belowground biomass. This study contributes a scientific basis for predicting how desert ecosystems may respond to future precipitation pattern changes and for understanding community succession mechanisms. It also holds important implications for functional trait–based ecological management strategies and biodiversity protecting.