Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China.
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China.
Sci Total Environ. 2021 Mar 20;761:143945. doi: 10.1016/j.scitotenv.2020.143945. Epub 2020 Dec 4.
Carbon sequestration is a key soil function, and an increase in soil organic carbon (SOC) is an indicator of ecosystem recovery because it underpins other ecosystem services by acting as a substrate for the soil microbial community. The soil microbial community constitutes the active pool of SOC, and its necromass (microbial residue carbon, MRC) contributes strongly to the stable SOC pool. Therefore, we propose that the potential for restoration of degraded karst ecosystems lies in the abundance of soil microbial community and the persistence of its necromass, and may be measured by changes in its contribution to the active and stable SOC pools during recovery. We investigated changes in SOC stocks using an established space-for-time chronosequence along a perturbation gradient in the subtropical karst ecosystem: sloping cropland < abandoned cropland < shrubland < secondary forest < primary forest. Microbial biomarkers were extracted from soil profiles from surface to bedrock and used to measure the contributions of the soil microbial community composition (using phospholipid fatty acids, PLFAs) and MRC (using amino sugars) to SOC stocks at each recovery stage. The results showed that the SOC stocks ranged from 10.53 to 31.77 kg m and increased with recovery stage, with total MRC accounting for 17-28% of SOC. Increasing PLFAs and MRC abundances were positively correlated with improved soil structure (decreased bulk density) and organic carbon, nitrogen and phosphorus nutrient. Bacterial MRC contributes more to SOC stocks than fungal residue carbon during vegetation recovery. The PLFA analysis indicated that Gram positive bacteria were the largest microbial group and were relatively more abundant in deeper soils, and biomarkers for saprophytic and ectomycorrhizal fungi were more abundant in soils under woody vegetation. In conclusion, this study suggests that the soil microbial community in karst soils have the potential to adapt to changing soil conditions and contribute substantially to building SOC stocks after abandonment of agriculture in degraded karst landscapes.
碳封存是土壤的一项关键功能，土壤有机碳 (SOC) 的增加是生态系统恢复的一个指标，因为它作为土壤微生物群落的基质，为其他生态系统服务提供支撑。土壤微生物群落构成了 SOC 的活性库，其残体（微生物残体碳，MRC）强烈地促进了稳定的 SOC 库。因此，我们提出，退化喀斯特生态系统恢复的潜力在于土壤微生物群落的丰度及其残体的持久性，并且可以通过其对恢复过程中 SOC 活性库和稳定库的贡献的变化来衡量。我们使用沿亚热带喀斯特生态系统的扰动梯度建立的时间序列空间来研究 SOC 储量的变化：坡耕地 < 撂荒地 < 灌丛 < 次生林 < 原始林。从土壤剖面中提取微生物生物标志物，从地表到基岩，用于测量土壤微生物群落组成（使用磷脂脂肪酸，PLFA）和 MRC（使用氨基糖）对每个恢复阶段 SOC 储量的贡献。结果表明，SOC 储量范围为 10.53 至 31.77 kg m，并随恢复阶段增加，总 MRC 占 SOC 的 17-28%。PLFA 和 MRC 丰度的增加与土壤结构（减少容重）以及有机碳、氮和磷养分的改善呈正相关。在植被恢复过程中，细菌 MRC 对 SOC 储量的贡献大于真菌残体碳。PLFA 分析表明，革兰氏阳性菌是最大的微生物群，在较深的土壤中相对更丰富，而腐生和外生菌根真菌的生物标志物在木本植被下的土壤中更为丰富。总之，本研究表明，喀斯特土壤中的土壤微生物群落具有适应土壤条件变化的潜力，并在退化喀斯特景观中农业弃耕后对 SOC 储量的形成做出了重要贡献。
