中文关键词农田撂荒土壤理化性质酶化学计量养分限制植物多样性 英文关键词farmland abandonmentsoil physicochemical propertiesenzymatic stoichiometrynutrient limitationplant diversity

作者	单位	E-mail
钟泽坤	西北农林科技大学农学院, 杨凌 712100 陕西省循环农业工程技术研究中心, 杨凌 712100	zhongzekun94@gmail.com
杨改河	西北农林科技大学农学院, 杨凌 712100 陕西省循环农业工程技术研究中心, 杨凌 712100	ygh@nwsuaf.edu.cn
任成杰	西北农林科技大学农学院, 杨凌 712100 陕西省循环农业工程技术研究中心, 杨凌 712100
韩新辉	西北农林科技大学农学院, 杨凌 712100 陕西省循环农业工程技术研究中心, 杨凌 712100

中文摘要 明确土壤胞外酶活性及酶化学计量比在农田撂荒过程中的变化特征及驱动因素，对揭示土壤养分可利用性随植被恢复的变化规律和阐明生态系统养分循环机制有重要意义.本文以黄土丘陵区不同撂荒年限坡耕地（0、10、20和30 a）为研究对象，通过测定土壤酶活性及酶计量比、土壤理化性质、植物多样性和科组成，探讨农田撂荒后土壤微生物养分限制状况及酶活性和酶计量比的主控因子.结果表明，β-1，4-N-乙酰氨基葡萄糖苷酶（NAG）、亮氨酸氨基肽酶（LAP）和碱性磷酸酶（ALP）的活性均随撂荒年限增加而显著增加，而β-1，4-葡萄糖苷酶（BG）活性则相反.土壤BG：（NAG+LAP）和BG：ALP呈现出与土壤BG活性相同的随撂荒年限增加而减小的趋势；而（NAG+LAP）：ALP呈先升后降趋势，在撂荒20 a时达到最高值.酶化学计量的向量长度随撂荒年限增加而显著减小，表明撂荒过程中土壤微生物受碳（C）限制程度的减弱.撂荒前10 a酶化学计量的向量角度小于45°，后20 a大于45°，说明撂荒前期微生物受氮（N）限制，后期受磷（P）限制.冗余分析结果揭示土壤有机碳含量、总氮含量、C：N、C：P、pH以及植被多样性是调控酶活性和酶计量比变化的主要因子.分类变异分析表明，土壤和植物因素可解释不同撂荒年限下土壤酶活性及酶计量比差异的62.0%，植被特征与土壤理化特性之间的交互作用是土壤酶活性及酶计量比变化的主控因子，解释度为37.1%.综上所述，黄土丘陵区农田撂荒过程中应考虑外源P的投入以缓解生态系统中有效P的不足，研究结果可为理解脆弱生境恢复生态系统中微生物介导的生物地球化学循环机制以及指导土壤养分管理和生态可持续发展提供理论依据. 英文摘要 Clarifying the characteristic of soil enzymatic activity and stoichiometry variations as well as their influencing factors following farmland abandonment have important implications for understanding soil nutrient availability after revegetation and for illuminating the underlying mechanisms of soil nutrient cycling in ecosystems. To determine microbial nutrient limitations after farmland abandonment and to explore the driving factors of the variations in soil enzymatic activity and stoichiometry along a chronosequence of abandoned farmlands (0-, 10-, 20-, and 30-year-old) in the Loess Hilly Region, China, the potential activities of carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzymes, soil physicochemical properties, and plant diversity and family composition were measured. The results showed that the activities of β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and alkaline phosphatase (ALP) increased significantly with the increasing years of land abandonment, whereas the activity of β-1,4-glucosidase (BG) showed the opposite change trend. Additionally, the ratios of BG:(NAG+LAP) and BG:ALP had the same variation trend with BG activity, which decreased significantly with increasing time, but the ratio of (NAG+LAP):ALP showed an increasing trend and then decreased, with the highest values observed in the 20-year sites. Moreover, the vector length of soil enzymatic stoichiometry decreased significantly as the years of land abandonment inceased, suggesting a reduced microbial C limitation after farmland abandonment. The vector angles <45°were observed at farmlands (0-year sites) and 10-year sites, whereas angles >45°were detected at 20-and 30-year sites, indicating that soil microbial communities were N-limited in the first 10 years of land abandonment and thereafter were P-limited. The redundancy analysis (RDA) reveled that soil organic C content, total N content, the C:N and C:P ratios, soil pH values, and plant diversity had significant effects on soil enzymatic activity and stoichiometry. A variation partitioning analysis (VPA) further demonstrated that edaphic and vegetation factors explained 62.0% of the total variance of soil enzymatic activity and stoichiometry. It should be noted that the interaction between vegetation characteristics and soil physicochemical properties was the major factor affecting soil enzymatic activity and stoichiometry, which explained 37.1% of the variance of the soil enzyme characteristics. Collectively, the application of P fertilizer should be considered to mitigate the deficiency of available P in the ecosystem during farmland abandonment, and these findings may provide a theoretical basis for understanding the mechanisms underlying microbe-mediated biogeochemical cycles as well as guiding soil nutrient management and the sustainable development of the ecological environment.

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