Abstract：
Dissolved organic carbon (DOC), the labile fraction of organic carbon, is a predominant substrate for microbes. Therefore, the turnover of DOC dominates microbial respiration in soils. We compiled a global dataset (1096 data points) of the turnover rates of DOC in 0-30 cm soil profiles and integrated the data with a machine learning algorithm to develop a global map of DOC turnover rate in global topsoil. The global DOC turnover rate in 0-30 cm soil was averaged as 0.0087 day-1, with a considerable variation among biomes. The fastest DOC turnover rate was found in tropical forests (0.0175 day-1) and the lowest in tundra (0.0036 day-1), exhibiting a declining trend from low to high latitudes. The DOC turnover rate is primarily controlled by edaphic and climate factors, as confirmed by the analyses with the structural equation model and the Mental\'s test. With a machine learning algorithm, we produced global maps of DOC turnover rate at a monthly scale, which were further combined with a global dataset of DOC density to produce monthly maps of carbon mineralization from DOC turnover in topsoil. The annual carbon release from DOC was estimated as 27.98 Pg C year-1 from topsoil across the globe, with the largest contribution from forest biomes, followed by pasture and grassland. Tundra released the least carbon from DOC due to its low turnover rate suppressed by low temperatures. The biome- and global-scale information of DOC turnover rate and carbon release from DOC provide a benchmark for ecosystem models to better project soil carbon dynamics and their contributions to global carbon cycling in the changing environment.
摘要：
溶解有机碳(DOC)有机碳的不稳定部分，是微生物的主要底物。因此,DOC的周转主导了土壤中的微生物呼吸。我们编制了0-30厘米土壤剖面中DOC周转率的全球数据集（1096个数据点），并将数据与机器学习算法集成，以开发全球表层土壤DOC周转率的全球图。0-30厘米土壤中的全球DOC周转率平均为0.0087天1，生物群落之间存在很大差异。DOC转换率最快的是热带森林（0.0175天-1），最低的是苔原（0.0036天-1），表现出从低纬度到高纬度的下降趋势。DOC周转率主要受地理和气候因素控制，结构方程模型和心理检验的分析证实了这一点。有了机器学习算法，我们每月制作了DOC周转率的全球地图，将其与DOC密度的全球数据集进一步结合，以从表层土壤中的DOC周转中产生碳矿化的月度图。DOC的年度碳释放量估计为27.98PgC年1，来自全球表层土壤，森林生物群落贡献最大，其次是牧场和草原。苔原从DOC中释放的碳最少，因为它的低转换率被低温抑制。DOC周转率和DOC碳释放的生物和全球尺度信息为生态系统模型提供了基准，以更好地预测土壤碳动态及其在不断变化的环境中对全球碳循环的贡献。
