Abstract: Deserts play a crucial role in the global carbon cycle, with plant carbon storage (PCS) and soil organic carbon storage (SOCS) being vital for regional ecological stability and climate regulation. We used structural equation modeling (SEM) to assess the effects of climatic factors, plant functional traits, and soil properties on PCS and SOCS across 56 sites in deserts of northwest China. Results showed that the mean PCS was 13.59 g·m^-2 (CV=0.54) and the mean SOCS reached 642.38 g·m^-2 (CV=0.27), with both exhibiting primary spatial variation at the site level. PCS was primarily influenced by mean annual precipitation, community weighted mean nitrogen content, community weighted mean plant height, and soil water content. Plant traits exerted a significant positive effect on vegetation carbon storage. SOCS was primarily influenced by mean annual temperature and soil total nitrogen. Temperature exerted a significant negative effect on SOCS directly and indirectly through its impact on plant community nitrogen content and soil nitrogen content. Nitrogen cycling played a crucial role in the formation and stabilization of carbon stocks in desert regions. Soil total nitrogen exerted a significant positive effect on SOCS, while plant community nitrogen content also significantly positively influenced PCS. Our results further revealed the spatial heterogeneity of carbon stocks in deserts, with the differences of sampling sites being the primary source of variation, indicating strong spatial variability. This study provides an important theoretical basis for understanding carbon cycling in deserts and offers key strategies for enhancing soil nitrogen retention and water use efficiency in these regions, as well as for addressing the vulnerability of carbon pools.

Key words: northwest China desert region, carbon stock, driving factor, soil organic carbon