Abstract Community composition and activity of soil microbes are responsive to changes in physiochemical and biological attributes during forest succession. However, whether soil microbial community structure and activity in soil particle-size fractions under different restoration approaches (regeneration through secondary succession and afforestation) during a chronosequence ranging from 20 to 70 years following deforestation of natural forest is still unclear. 24 soil samples from the top 10 cm of soil profiles were collected for four stand ages of spruce plantations and natural birch forests from three different sites. Soil aggregates were fractionated with dry-sieving technique and soil microbial communities in soil particle-size fractions were characterized by PLFAs profiling and enzymatic activity assay. The effects of restoration approach, soil aggregate-size and stand age on soil microbial biomass were depended on microbial group identity. Differences in microbial biomass were correlated to soil organic carbon, total nitrogen and pH. Additionally, differences in soil organic carbon, total nitrogen, pH and C:N ratio across restoration approaches, soil aggregate-sizes and stand ages jointly regulated soil microbial community composition. Soil aggregate-size and stand age also exerted significant effects on the potential activities of β-1, 4-glucosidase (βG), β-1, 4-N-acetyl-glucosaminidase (NAG), acid phosphatase (ACP) and polyphenol oxidase (POX), while the effect of restoration approach on enzyme activities depended on the enzyme identity. Soil organic carbon, total nitrogen were major predictors of enzymatic activity in particle-size fractions. The carbon quality index ( CQI = lnPOX / ( ln β G + lnPOX ) ) rather than soil quality index (SQI = ( β G*NAG*ACP*POX 4 ) ) was a promising indicator of the response of soil microbial activity to restoration approach and stand age. In conclusion, the effects of restoration approach on soil microbial biomass and enzymatic activity vary depending on aggregate-size and stand age. Soil microbial biomass, community structure and enzymatic activity provide evidence that natural restoration enhancing soil quality in comparison with artificial restoration in the fragile subalpine forest ecosystem.

中文翻译：

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云杉人工林和次生桦林土壤颗粒级分的土壤微生物群落和酶活性

摘要 土壤微生物群落组成和活动对森林演替过程中理化和生物属性的变化有响应。然而，在天然林砍伐后 20 至 70 年的时间序列中，不同恢复方法（通过次生演替和造林再生）下土壤微生物群落结构和土壤颗粒大小部分的活性是否仍不清楚。从三个不同地点的云杉种植园和天然桦树林的四个林龄收集了土壤剖面顶部 10 厘米的 24 个土壤样品。土壤团聚体采用干筛技术进行分级，土壤颗粒级分中的土壤微生物群落通过 PLFA 分析和酶活性测定进行表征。恢复方法的效果，土壤团聚体大小和林龄对土壤微生物生物量的影响取决于微生物群的特征。微生物生物量的差异与土壤有机碳、总氮和 pH 值相关。此外，不同恢复方法、土壤团聚体大小和林龄的土壤有机碳、总氮、pH 值和 C:N 比的差异共同调节了土壤微生物群落组成。土壤团聚体大小和林龄也对 β-1, 4-葡萄糖苷酶 (βG)、β-1, 4-N-乙酰氨基葡萄糖苷酶 (NAG)、酸性磷酸酶 (ACP) 和多酚氧化酶的潜在活性产生显着影响(POX)，而恢复方法对酶活性的影响取决于酶的特性。土壤有机碳、总氮是粒度级分中酶活性的主要预测因子。碳质量指数( CQI = lnPOX / ( ln β G + lnPOX ) ) 而不是土壤质量指数(SQI = ( β G*NAG*ACP*POX 4 ) ) 是土壤微生物活动对恢复响应的有希望的指标接近和站立年龄。总之，修复方法对土壤微生物生物量和酶活性的影响取决于团聚体大小和林龄。土壤微生物生物量、群落结构和酶活性提供的证据表明，与脆弱的亚高山森林生态系统中的人工修复相比，自然修复可提高土壤质量。恢复方法对土壤微生物生物量和酶活性的影响取决于团聚体大小和林龄。土壤微生物生物量、群落结构和酶活性提供的证据表明，与脆弱的亚高山森林生态系统中的人工修复相比，自然修复可提高土壤质量。恢复方法对土壤微生物生物量和酶活性的影响取决于团聚体大小和林龄。土壤微生物生物量、群落结构和酶活性提供的证据表明，与脆弱的亚高山森林生态系统中的人工修复相比，自然修复可提高土壤质量。