Simulated Root Exudation Gradient Reveals Dosage‐Dependent Carbon Sequestration in Desertification Ecosystems

ABSTRACT

Root exudates serve as a key driver for the restoration of soil organic carbon (SOC), particularly in aeolian desertification ecosystems where aboveground litter retention is limited. While Salix cupularis is widely planted as an effective pioneer shrub for ecological rehabilitation on the Qinghai‐Tibet Plateau, how the quantity of its root exudates regulates the dynamics of microbial‐derived SOC in sandy soils remains unclear. Using ¹³ C isotope labeling and DNA‐SIP, we simulated the root carbon exudation of S. cupularis with a glucose gradient: ambient rate (V), half the ambient rate (1/2 V), and twice the ambient rate (2 V) to investigate carbon decomposition pathways in sandy soil. We found that different glucose input levels significantly altered soil carbon components and enriched distinct microbial communities. Under V treatment, a higher proportion of glucose was efficiently incorporated into particulate organic carbon (POC). Conversely, both the 1/2 V and 2 V treatments diverted more glucose toward microbial respiration. While 1/2 V treatment increased microbial biomass, it simultaneously induced a positive priming effect, thereby exacerbating native soil carbon loss. Meanwhile, 2 V treatment significantly reduced microbial diversity and further elevated respiration, resulting in the lowest carbon sequestration efficiency. This study elucidates the mechanisms underlying microbial adaptation to varying nutrient inputs and reveals the dosage‐dependent advantage of S. cupularis root exudation in maintaining soil carbon balance. These findings offer novel perspectives on optimizing carbon sequestration strategies and understanding the ecological restoration capacity of pioneer plants in desertified ecosystems.