Effects of environmental changes on soil respiration in arid, cold, temperate, and tropical zones

Soil respiration (R_s) is projected to be substantially affected by climate change, impacting the storage, equilibrium, and movement of terrestrial carbon (C). However, uncertainties surrounding the responses of R_s to climate change and soil nitrogen (N) enrichment are linked to mechanisms specific to diverse climate zones. A comprehensive meta-analysis was conducted to address this, evaluating the global effects of warming, increased precipitation, and N enrichment on R_s across various climate zones and ecosystems. Data from 123 studies, encompassing a total of 10,377 worldwide observations, were synthesized for this purpose. Annual R_s were modeled and their uncertainties were associated with a 1-km² resolution global R_s database spanning from 1961 to 2022. Calibrating R_s using ensemble machine learning (EML) and employing 10-fold cross-validation, 13 environmental covariates were utilized. The meta-analysis findings revealed an upsurge in R_s rates in response to warming, with tropical, arid, and temperate climate zones exhibiting increases of 12 %, 13 %, and 16 %, respectively. Furthermore, increased precipitation led to stimulated R_s rates of 11 % and 9 % in tropical and temperate zones, respectively, while N deposition affected R_s in cold (+6 %) and tropical (+5 %) climate zones. The machine learning technique estimated the global soil respiration to range from 91 to 171 Pg C yr^-1, with an average R_s of 700 ± 300 g C m^-2 yr^-1. The values ranged between 314 and 2500 g C m^-2 yr^-1, with the lowest and highest values observed in cold and tropical zones, respectively. Spatial variation in R_s was most pronounced in low-latitude areas, particularly in tropical rainforests and monsoon zones. Temperature, precipitation, and N deposition were identified as crucial environmental factors exerting significant influences on R_s rates worldwide. These factors underscore the interconnectedness between climate and ecosystem processes, therefore requiring explicit considerations of different climate zones when assessing responses of R_s to global change.