Responses of dryland soil respiration and soil carbon pool size to abrupt vs. gradual and individual vs. combined changes in soil temperature, precipitation, and atmospheric [CO₂]: a simulation analysis

With the large extent and great amount of soil carbon (C) storage, drylands play an important role in terrestrial C balance and feedbacks to climate change. Yet, how dryland soils respond to gradual and concomitant changes in multiple global change drivers [e.g., temperature ( T s ), precipitation (Ppt), and atmospheric [CO 2 ] (CO 2 )] has rarely been studied. We used a process‐based ecosystem model patch arid land simulator to simulate dryland soil respiration ( R s ) and C pool size ( C s ) changes to abrupt vs. gradual and single vs. combined alterations in T s , Ppt and CO 2 at multiple treatment levels. Results showed that abrupt perturbations generally resulted in larger R s and had longer differentiated impacts than did gradual perturbations. R s was stimulated by increases in T s , Ppt, and CO 2 in a nonlinear fashion (e.g., parabolically or asymptotically) but suppressed by Ppt reduction. Warming mainly stimulated heterotrophic R s (i.e., R h ) whereas Ppt and CO 2 influenced autotrophic R s (i.e., R a ). The combined effects of warming, Ppt, and CO 2 were nonadditive of primary single‐factor effects as a result of substantial interactions among these factors. Warming amplified the effects of both Ppt addition and CO 2 elevation whereas Ppt addition and CO 2 elevation counteracted with each other. Precipitation reduction either magnified or suppressed warming and CO 2 effects, depending on the magnitude of factor's alteration and the components of R s ( R a or R h ) being examined. Overall, Ppt had dominant influence on dryland R s and C s over T s and CO 2 . Increasing Ppt individually or in combination with T s and CO 2 benefited soil C sequestration. We therefore suggested that global change experimental studies for dryland ecosystems should focus more on the effects of precipitation regime changes and the combined effects of Ppt with other global change factors (e.g., T s , CO 2 , and N deposition).