Which contributes more in predictor of desert shrubs traits: Intra-annual or inter-annual precipitation change?

Abstract

Considering the implications of future climatic shifts, mid-latitude desert ecosystems will experience pronounced changes in precipitation dynamics, as evidenced by the elevated inter-annual variability and escalated annual incidence of extreme rainfall events. Despite considerable research on vegetation response to intricate precipitation patterns at the community level, the physiological adaptations of individual plants within these assemblages are not well defined. This investigation employed simulations of diverse precipitation scenarios, utilising varying precipitation amounts (to simulate inter-annual variability) and intervals (to simulate intra-annual variability). A field-manipulated experiment was conducted to assess the responses of the leaf and stem hydraulic functional traits of Artemisia ordosica under different precipitation regimes. The results demonstrated that 1) the magnitude of inter-annual precipitation, rather than the intra-annual redistribution of precipitation, dominated the variability in the functional traits of A. ordosica, with diminished inter-annual precipitation inducing an array of functional trait alterations (e.g., specific leaf area, stomatal conductance, water use efficiency, and conduit diameter) to enhance water-use safety. Reallocating precipitation to low-frequency but high-intensity events during years with less inter-annual precipitation was more advantageous for the survival of A. ordosica. 2) A reduction in annual precipitation fostered a correlation between stem and leaf functional traits in A. ordosica (e.g., hydraulic conductance with photosynthetic rate, stomatal conductance, conduit diameter with transpiration rate, and water use efficiency), suggesting that under decreased precipitation, A. ordosica strengthens the coupling between hydraulics and photosynthesis to prevent hydraulic failure, demonstrating a safer survival strategy. Overall, the impact of global changes in precipitation patterns on the individual survival of A. ordosica primarily depended on the variation in inter-annual precipitation rather than the within-year redistribution. This study enhanced our understanding of the adaptability of dominant shrub species within desert shrub communities to altered precipitation patterns under climate change.