State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China; University of Chinese Academy of Sciences, Beijing 100049, China.
College of Forestry, Northwest A&F University, Yangling, Shaanxi 712100, China.
Sci Total Environ. 2019 Nov 25;693:133613. doi: 10.1016/j.scitotenv.2019.133613. Epub 2019 Jul 27.
Vegetation restoration after farmland abandonment has increased greatly and is commonly used to improve soil fertility and ecosystem service. Knowledge of soil community-level elemental homeostasis following natural vegetation restoration is specially limited for the abandoned farmlands. This study examined the changes in soil microbial biomass stoichiometry and homeostasis with a chronosequence of 3, 8, 13, 18, 23 and 30 years following natural vegetation restoration since farmland abandonment on the Loess Plateau, China. Vegetation communities, soil properties, microbial communities, and enzyme activities were analyzed to study the drivers on soil microbial C:N:P stoichiometry. The results showed that soil microbial biomass C: N ratios had little change following natural vegetation restoration since farmland abandonment, natural vegetation >23 years had significantly enhanced the microbial biomass C:P and N:P ratios by 26.1%-133.9% and 31.7%-67.4%, respectively. However, microbial biomass C:N, C:P and N:P ratios were constrained following natural vegetation restoration. Vegetation restoration for 30 years enhanced urease and alkaline phosphatase activities by 125.4% and 42.9%, respectively, which showed synchronous changes with N and P contents in microbial biomass. Soil fungi, urease and alkaline phosphatase were the drivers to the changes in microbial C:N:P stoichiometry. The results suggest that long-term vegetation restoration (>23 years) will aggravate microbial P limitation, however, soil microorganism maintained the homeostatic regulation of stoichiometric ratios to mitigate P limitation. Fungi played a strong role in shaping microbial community-level elemental homeostasis and nutrient cycling through releasing N-converting and P-converting enzymes into soil following natural vegetation restoration.
农田弃耕后，植被恢复的面积大大增加，通常用于提高土壤肥力和生态系统服务。然而，对于废弃农田，自然植被恢复后土壤群落水平元素内稳性的知识特别有限。本研究通过中国黄土高原农田弃耕后自然植被恢复的 3、8、13、18、23 和 30 年的时间序列，研究了土壤微生物生物量化学计量和内稳性的变化。分析了植被群落、土壤性质、微生物群落和酶活性，以研究土壤微生物 C:N:P 化学计量的驱动因素。结果表明，农田弃耕后自然植被恢复对土壤微生物生物量 C:N 比影响较小，自然植被>23 年通过 26.1%-133.9%和 31.7%-67.4%分别显著增强了微生物生物量 C:P 和 N:P 比。然而，微生物生物量 C:N、C:P 和 N:P 比受到自然植被恢复的限制。植被恢复 30 年增强了脲酶和碱性磷酸酶活性，分别提高了 125.4%和 42.9%，这与微生物生物量中的 N 和 P 含量同步变化。土壤真菌、脲酶和碱性磷酸酶是微生物 C:N:P 化学计量变化的驱动因素。结果表明，长期植被恢复（>23 年）将加剧微生物 P 限制，但土壤微生物通过向土壤中释放 N 转化和 P 转化酶来维持化学计量比的内稳性调节以减轻 P 限制。真菌通过向土壤中释放 N 转化和 P 转化酶，在自然植被恢复后通过释放 N 转化和 P 转化酶，在塑造微生物群落水平元素内稳性和养分循环方面发挥了强大作用。
