不同林龄杉木林土壤细菌群落结构与土壤酶活性变化研究

探究不同林龄杉木人工纯林土壤中的微生物的群落演变与结构特征与酶活性变化，为杉木人工林可持续经营管理提供依据。以福建省南平市的五片不同林龄杉木林表层土壤作为研究对象，通过16SrDNA测定细菌的群落组成，分析与土壤质量密切相关的四种土壤酶活性变化，揭示细菌群落与土壤酶活性的变化机理。结果表明，微生物的多样性指数与OTU都随着林龄的增加而增加，且幼龄林、中龄林、近熟林、成熟林土壤微生物结构差异较大；不同林龄杉木人工林中包含了29个细菌门，其中酸杆菌门与变形菌门为优势菌群，根据各种群相对丰度变化以及冗余分析，放线菌门、浮霉菌门与疣微菌门等均随林龄增长出现较大变化，且与土壤可溶性有机质以及速效养分有显著相关性（P<0.05），说明这几种细菌群落对土壤养分变化较敏感；土壤养分变化会影响土壤酶活性，蔗糖酶与全碳呈显著正相关（P<0.05），与速效钾呈显著负相关（P<0.05），与放线菌门呈极显著负相关（P<0.01）。脲酶与速效氮呈显著负相关（P<0.05），脲酶与变形菌门、绿弯菌门、放线菌门、硝化螺旋菌门以及拟杆菌门均存在较强相关性。综上，不同的土壤细菌种群与酶活性对各养分变化的响应程度不一，细菌群落结构与酶活性能反映不同林龄杉木林土壤的质量变化，适量延长杉木人工林种植年限有益于土壤质量恢复。本研究结果对指导杉木人工林优质经营有重要意义。

Changes of soil bacterial structure and soil enzyme activity in Chinese fir forest of different ages

In order to understand the changes in the soils of Chinese fir plantations at different ages, this article explores the response mechanism of soil microorganisms and enzyme activity to forest age growth, providing a basis for sustainable management of Chinese fir plantations. Five Chinese fir forests of different ages were targeted in Nanping. 16sRDNA was used to study the composition of the bacterial community, and four enzyme activity changes closely related to soil quality were analyzed. The results showed that both the microbial diversity index and OTU (Operational Taxonomic Units) increased with the increase of forest age. The soil microbial structure of young forests, middle-aged forests, near-maturity forests, and mature forests had large differences. There were 29 bacterial phylums in different ages of Chinese fir plantations. Acidobacteria and Proteobacteria were the dominant species.According to the changes of various groups and redundant analysis, Actinomycota, Verrucomicrobia, and Planctomycetes all changed significantly with age, and they were significantly related to soil dissolved organic matter and available nutrients (P<0.05). It shows that these bacterial communities are more sensitive to changes in soil quality. Soil nutrient changes affected soil enzyme activity. Sucrase had a significant positive correlation with total carbon (P<0.05) and negative correlation with available potassium (P<0.05), and a very significant negative correlation with actinomycetes (P<0.01). There was a strong correlation between urease and available nitrogen (P<0.05). Urease was strongly correlated with Proteobacteria, Chloroflexi, Actinobacteria, Nitrospirae, Bacteroidetes. In summary, soil nutrient changes have different effects on soil bacterial populations and enzyme activities. Bacterial community structure and enzyme activity can reflect changes in soil quality of Chinese fir forest at different ages. Extending the planting period of Chinese fir plantation is beneficial to the restoration of soil quality.The results of this study are of great significance for guiding the management of Chinese fir plantations.