Effects of carbon turnover time on terrestrial ecosystem carbon storage

摘要

Carbon (C) turnover time is a key factor in determining C storage capacity in various plant and soil pools as well as terrestrial C sink in a changing climate. However, the effects of C turnover time on ecosystem C storage have not been well explored. In this study, we compared mean C turnover times (MTTs) of ecosystem and soil, examined their variability to climate, and then quantified the spatial variation in ecosystem C storage over time from changes in C turnover time and/or net primary production (NPP). Our results showed that mean ecosystem MTT based on gross primary production (GPP; MTTsubECi_/iGPP/sub?=??Csubpool/sub/GPP, 25.0?±?2.7?years) was shorter than soil MTT (MTTsubsoil/sub?=??Csubsoil/sub/NPP, 35.5?±?1.2?years) and NPP-based ecosystem MTT (MTTsubECi_/iNPP/sub?=??Csubpool/sub/NPP, 50.8?±?3?years; Csubpool/sub and Csubsoil/sub referred to ecosystem or soil C storage, respectively). On the biome scale, temperature is the best predictor for MTTsubEC/sub (iR/isup2/sup?=??0.77, ip/i?&?0.001) and MTTsubsoil/sub (iR/isup2/sup?=??0.68, ip/i?&?0.001), while the inclusion of precipitation in the model did not improve the performance of MTTsubEC/sub (iR/isup2/sup?=??0.76, ip/i?&?0.001). Ecosystem MTT decreased by approximately 4?years from 1901 to 2011 when only temperature was considered, resulting in a large C release from terrestrial ecosystems. The resultant terrestrial C release caused by the decrease in MTT only accounted for about 13.5?% of that due to the change in NPP uptake (159.3?±?1.45 vs. 1215.4?±?11.0?Pg?C). However, the larger uncertainties in the spatial variation of MTT than temporal changes could lead to a greater impact on ecosystem C storage, which deserves further study in the future.