National Engineering Laboratory for Improving Quality of Arable Land, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China.
Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, USA.
Glob Chang Biol. 2017 Nov;23(11):4765-4776. doi: 10.1111/gcb.13755. Epub 2017 Jun 9.
Quantifying soil organic carbon (SOC) decomposition under warming is critical to predict carbon-climate feedbacks. According to the substrate regulating principle, SOC decomposition would decrease as labile SOC declines under field warming, but observations of SOC decomposition under warming do not always support this prediction. This discrepancy could result from varying changes in SOC components and soil microbial communities under warming. This study aimed to determine the decomposition of SOC components with different turnover times after subjected to long-term field warming and/or root exclusion to limit C input, and to test whether SOC decomposition is driven by substrate lability under warming. Taking advantage of a 12-year field warming experiment in a prairie, we assessed the decomposition of SOC components by incubating soils from control and warmed plots, with and without root exclusion for 3 years. We assayed SOC decomposition from these incubations by combining inverse modeling and microbial functional genes during decomposition with a metagenomic technique (GeoChip). The decomposition of SOC components with turnover times of years and decades, which contributed to 95% of total cumulative CO respiration, was greater in soils from warmed plots. But the decomposition of labile SOC was similar in warmed plots compared to the control. The diversity of C-degradation microbial genes generally declined with time during the incubation in all treatments, suggesting shifts of microbial functional groups as substrate composition was changing. Compared to the control, soils from warmed plots showed significant increase in the signal intensities of microbial genes involved in degrading complex organic compounds, implying enhanced potential abilities of microbial catabolism. These are likely responsible for accelerated decomposition of SOC components with slow turnover rates. Overall, the shifted microbial community induced by long-term warming accelerates the decomposition of SOC components with slow turnover rates and thus amplify the positive feedback to climate change.
量化变暖条件下土壤有机碳（SOC）的分解对于预测碳-气候反馈至关重要。根据底物调节原理，在田间变暖条件下，不稳定 SOC 减少，SOC 分解应该会减少，但变暖条件下 SOC 分解的观测结果并不总是支持这一预测。这种差异可能是由于变暖条件下 SOC 组分和土壤微生物群落的变化所致。本研究旨在确定长期田间变暖以及/或者根系排除（以限制 C 输入）处理后具有不同周转时间的 SOC 组分的分解，并检验变暖条件下 SOC 分解是否受底物易变性的驱动。本研究利用草原 12 年田间变暖实验，通过在有根和无根（以限制 C 输入）条件下培养对照和变暖处理的土壤 3 年，评估 SOC 组分的分解。通过结合反演模型和微生物功能基因（利用宏基因组技术（GeoChip）），对这些培养物中的 SOC 分解进行分析。在所有处理中，贡献了 95%的总累积 CO2 呼吸的年和十年周转时间的 SOC 组分的分解在变暖处理的土壤中更大。但与对照相比，变暖处理的土壤中易变 SOC 的分解相似。在所有处理中，随着培养时间的推移，C 降解微生物基因的多样性普遍下降，这表明随着底物组成的变化，微生物功能群发生了转变。与对照相比，变暖处理的土壤中与降解复杂有机化合物相关的微生物基因的信号强度显著增加，这意味着微生物代谢能力增强。这可能是导致 SOC 组分分解加快的原因，因为这些 SOC 组分的周转时间较长。总的来说，长期变暖引起的微生物群落的转变加速了 SOC 组分的分解，从而放大了对气候变化的正反馈。
