Carbohydrate allocation strategies in leaves of dominant desert shrubs in response to precipitation variability

Climate change has significantly altered precipitation patterns worldwide, resulting in more frequent and intense droughts and heavy rainstorms, particularly in vulnerable ecosystems such as arid deserts. This study investigated how dominant desert shrubs, the C₃ plant Kalidium gracile and the C₄ plant Salsola passerina, respond to varying precipitation regimes. A six-year controlled experiment (2016–2021) employing a five-level precipitation gradient, ranging from extreme drought to increased water availability, was conducted to elucidate changes in leaves carbon content and its components under these conditions. Results indicated a substantial increase in starch (ST) content in S. passerina under heightened rainfall conditions (P < 0.05), whereas K. gracile showed a propensity tendency to accumulate ST content under moderate drought condition. These findings indicated distinct adaptive strategies between the two species in response to water availability. Additionally, both shrubs maintained a relatively stable ratio of non-structural carbohydrates (NSC) to structural carbohydrates (SC) (P > 0.05), suggesting an active regulation of carbon balance within plant structures, independent of precipitation changes. Notably, S. passerina demonstrated greater responsiveness to precipitation alterations compared to K. gracile, highlighting species-specific differences in carbon allocation strategies. This study provides mechanistic insights into plant carbon dynamics in response to precipitation changes in desert ecosystems, contributing to a deeper understanding of carbon cycling processes and ecosystem functioning in arid landscapes.