Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, PR China.
College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
Sci Total Environ. 2018 Nov 1;640-641:653-661. doi: 10.1016/j.scitotenv.2018.05.332. Epub 2018 Jun 2.
The fate of soil organic carbon (SOC) sequestered by afforestation is crucial for the mitigation of the anthropogenic climate change but remains largely unclear. This lack of knowledge is particularly true for SOC turnover driven by enzyme activity. Here we measured hydrolase (including β-glucosidase, α-glucosidase, cellobiohydrolase and xylanase) and oxidase (including polyphenol oxidase and peroxidase) activities in soil aggregates following 30-year afforestation in central China. We also analyzed the relationships of enzyme activities with SOC concentrations, soil C:nitrogen (N) ratios and δC values of soil organic pool (removing any carbonates by acid hydrolysis) and stable pool (NaOCl-resistant). Afforestation significantly enhanced soil β-glucosidase, α-glucosidase and xylanase activities in bulk soil, as well as SOC concentrations in bulk soil and all aggregate fractions compared to those in the open area and cropland. In particular, the woodland increased SOC concentration in >2000 μm macroaggregates by 4.2- and 3.2-fold, compared to the open area and cropland, respectively. Soil hydrolase activities were generally lower but SOC concentrations were higher in >2000 μm macroaggregates compared with those in other aggregate fractions following afforestation. Hydrolase activities were negatively correlated with SOC and C:N ratios in soil aggregate fractions following afforestation. Results of structural equation modeling indicated that the increasingly inhibited hydrolase activities with increasing soil aggregate size indirectly promoted SOC sequestration following afforestation. In addition, both hydrolase and oxidase were positively correlated with δC values in the stable pool of the afforested soils, confirming the essential role of enzymes for SOC turnover in soil aggregates following afforestation. Overall, our results highlight the importance of unevenly distributed enzyme activities among soil aggregates in regulating SOC sequestration following afforestation.
造林固存的土壤有机碳（SOC）的命运对缓解人为气候变化至关重要，但目前仍不清楚。对于酶活性驱动的 SOC 转化，这种知识的缺乏尤其明显。本研究通过 30 年的造林实验，测量了中国中部造林后土壤团聚体中的水解酶（包括β-葡萄糖苷酶、α-葡萄糖苷酶、纤维二糖水解酶和木聚糖酶）和氧化酶（包括多酚氧化酶和过氧化物酶）活性，并分析了酶活性与 SOC 浓度、土壤 C：N 比以及土壤有机库（通过酸水解去除任何碳酸盐）和稳定库（NaOCl 抗性）δC 值的关系。与空旷地和农田相比，造林显著提高了土壤的β-葡萄糖苷酶、α-葡萄糖苷酶和木聚糖酶活性，以及土壤总有机碳浓度和所有团聚体的 SOC 浓度。特别是，与空旷地和农田相比，林地分别将>2000μm大团聚体中的 SOC 浓度提高了 4.2 倍和 3.2 倍。与其他团聚体相比，造林后>2000μm大团聚体中的水解酶活性通常较低，但 SOC 浓度较高。造林后，土壤团聚体中水解酶活性与 SOC 和 C：N 比呈负相关。结构方程模型的结果表明，随着土壤团聚体粒径的增大，水解酶活性受到越来越大的抑制，这间接促进了造林后 SOC 的固存。此外，水解酶和氧化酶与造林土壤稳定库的 δC 值呈正相关，这证实了酶在造林后土壤团聚体中 SOC 转化中的重要作用。总的来说，我们的结果强调了土壤团聚体中不均匀分布的酶活性在调节造林后 SOC 固存方面的重要性。
