A global meta-analysis of soil respiration and its components in response to phosphorus addition

Increasing phosphorus (P) deposition induced by anthropogenic activities has increased the availability of P, and thus could affect ecosystem carbon cycling. Although soil respiration (Rs) plays a crucial role in driving the global carbon cycle and regulating climate warming, a general pattern reflecting the Rs response to P addition in terrestrial ecosystems remains unclear. Here, we conducted a meta-analysis from 102 publications to explore the generalities and mechanisms of responses of Rs and its components to P addition across various ecosystems at the global scale. Our results showed that P addition did not significantly change Rs and heterotrophic respiration (Rh) across all ecosystems, but this P addition effect varied among ecosystem types (p < 0.05). Specifically, P addition significantly increased Rs by 17.4% in tropical forest and by 31.7% in cropland, depressed Rs by 13.7% in wetland (p < 0.05), and had minor effect in other ecosystems (grassland, boreal forest, and temperate forest). In contrast, P addition did not have significant effect on Rh within any specific ecosystem type. Among multiple environmental and experimental variables, mean annual temperature might be the fundamental driver indirectly controlling the response of Rs to P addition at the large scale. In addition, P addition increased soil P availability, and changed ecosystem carbon pools and fluxes. The responses of Rs and Rh were significantly positively correlated with those of soil organic carbon, microbial biomass carbon and belowground biomass, respectively, suggesting that changes of these carbon pools may drive the responses of Rs and Rh to P addition. Collectively, our findings imply that Rs in tropical forests would strongly respond to P enrichment where current soil P availability is low and future P deposition rate is high, provide a framework for understanding Rs dynamics under global P deposition, and highlight the need for further field studies partitioning the two components of Rs.