Abstract Soil is the largest organic carbon (C) pool of terrestrial ecosystems, and C loss from soil accounts for a large proportion of land‐atmosphere C exchange. Therefore, a small change in soil organic C (SOC) can affect atmospheric carbon dioxide (CO2) concentration and climate change. In the past decades, a wide variety of studies have been conducted to quantify global SOC stocks and soil C exchange with the atmosphere through site measurements, inventories, and empirical/process‐based modeling. However, these estimates are highly uncertain, and identifying major driving forces controlling soil C dynamics remains a key research challenge. This study has compiled century‐long (1901–2010) estimates of SOC storage and heterotrophic respiration (Rh) from 10 terrestrial biosphere models (TBMs) in the Multi‐scale Synthesis and Terrestrial Model Intercomparison Project and two observation‐based data sets. The 10 TBM ensemble shows that global SOC estimate ranges from 425 to 2111 Pg C (1 Pg = 1015 g) with a median value of 1158 Pg C in 2010. The models estimate a broad range of Rh from 35 to 69 Pg C yr−1 with a median value of 51 Pg C yr−1 during 2001–2010. The largest uncertainty in SOC stocks exists in the 40–65°N latitude whereas the largest cross‐model divergence in Rh are in the tropics. The modeled SOC change during 1901–2010 ranges from −70 Pg C to 86 Pg C, but in some models the SOC change has a different sign from the change of total C stock, implying very different contribution of vegetation and soil pools in determining the terrestrial C budget among models. The model ensemble‐estimated mean residence time of SOC shows a reduction of 3.4 years over the past century, which accelerate C cycling through the land biosphere. All the models agreed that climate and land use changes decreased SOC stocks, while elevated atmospheric CO2 and nitrogen deposition over intact ecosystems increased SOC stocks—even though the responses varied significantly among models. Model representations of temperature and moisture sensitivity, nutrient limitation, and land use partially explain the divergent estimates of global SOC stocks and soil C fluxes in this study. In addition, a major source of systematic error in model estimations relates to nonmodeled SOC storage in wetlands and peatlands, as well as to old C storage in deep soil layers.

中文翻译：

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多个陆地生物圈模型模拟的土壤有机碳动态的全球模式和控制：现状和未来方向


摘要 土壤是陆地生态系统最大的有机碳库，土壤碳流失在陆地-大气碳交换中占有很大比例。因此，土壤有机碳（SOC）的微小变化就会影响大气二氧化碳（CO2）浓度和气候变化。在过去的几十年中，人们进行了各种各样的研究，通过现场测量、清单和基于经验/过程的建模来量化全球 SOC 储量以及土壤 C 与大气的交换。然而，这些估计具有很大的不确定性，确定控制土壤碳动态的主要驱动力仍然是一个关键的研究挑战。本研究根据多尺度综合和陆地模型比对项目中的 10 个陆地生物圈模型 (TBM) 和两个基于观测的数据集，编制了长达一个世纪 (1901-2010) 的 SOC 储存和异养呼吸 (Rh) 估计值。 10 TBM 系综显示，全球 SOC 估算范围为 425 至 2111 Pg C（1 Pg = 1015 g），2010 年中值为 1158 Pg C。模型估算的 Rh 范围广泛，从 35 至 69 Pg C yr− 1，2001-2010 年期间中值为 51 Pg C yr−1。 SOC 储量最大的不确定性存在于北纬 40-65° 纬度，而 Rh 的最大跨模型差异则存在于热带地区。 1901-2010 年期间模拟的 SOC 变化范围为 -70 Pg C 至 86 Pg C，但在某些模型中，SOC 变化与总碳库变化具有不同的迹象，这意味着植被和土壤库在确定模型之间的地面 C 预算。模型集合估计的 SOC 平均停留时间比上个世纪减少了 3.4 年，这加速了陆地生物圈的碳循环。 所有模型都一致认为，气候和土地利用变化减少了 SOC 储量，而完整生态系统上大气二氧化碳和氮沉降的增加则增加了 SOC 储量，尽管模型之间的响应差异很大。温度和湿度敏感性、养分限制和土地利用的模型表示部分解释了本研究中对全球有机碳储量和土壤碳通量的不同估计。此外，模型估计中系统误差的一个主要来源与湿地和泥炭地中未建模的 SOC 存储以及深层土壤层中旧的 C 存储有关。