不同林龄杉木+闽楠复层林土壤磷形态及微生物功能多样性变化

磷是限制亚热带地区林木生长的关键因素之一，研究土壤微生物群落功能多样性对土壤磷素的影响，对亚热带地区人工林可持续经营具有重要意义。在江西官山林场选取了3种不同林龄杉木+闽楠（4 a、7 a、11 a）复层林为研究对象，测定了土壤全磷、有效磷及无机磷组分含量，采用Biolog-ECO法研究了复层林表土层（0-20 cm）土壤微生物群落对碳源的利用特征，并分析了土壤磷素与土壤微生物功能多样性的关系。结果表明：（1）土壤全磷、有效磷及无机磷组分含量随复层林营建时间延长呈增加趋势；（2）不同林分类型土壤微生物群落功能多样性差异显著。土壤微生物碳源代谢活性（AWCD）以及多样性指数也均随复层林营建时间延长呈增加趋势；多聚物类是杉木纯林土壤微生物利用的主要碳源，7 a复层林对碳水化合物、羧酸和酚酸的利用强度较大，11 a复层林对氨基酸、胺类、多聚物、羧酸和酚酸的利用强度较大，并且11 a复层林土壤微生物群落代谢碳水化合物、氨基酸、羧酸、胺类和酚酸的强度显著高于4 a复层林和杉木纯林，而4 a复层林与杉木纯林土壤微生物群落对不同碳源利用率的差异较小（除多聚物外）。（3）土壤微生物多样性指数、氨基酸类、胺类和酚酸类物质与土壤全磷、有效磷、Al-P和Fe-P含量之间显著正相关，随机森林模型分析表明，氨基酸、胺类和酚酸是不同林分类型土壤微生物利用的主要碳源。因此，杉木纯林转化为复层异龄林更有利于森林土壤磷的储存和供应，土壤微生物群落代谢功能多样性的增大可能是提高复层异龄林土壤磷有效性的关键调控因素。

Variations of soil phosphorus form and microbial functional diversity in Cunninghumia lanceolata+Phoebe bournei multi-layered mixed plantations of different ages

Phosphorus is considered a key factor of limiting the forests growth in subtropical areas. Understanding the effects of soil microbial functional diversity on soil phosphorus is important for sustainable management of plantations in subtropical areas. Three C. lanceolata + P. bournei (4a,7a,11a) multi-layered mixed plantations were selected in Guanshan Forest Farm, Jiangxi Province. The contents of total phosphorus, available phosphorus, and inorganic phosphorus were determined in these stands. Biology-ECO method was used to study the characteristics of carbon utilization by soil microorganisms in the topsoil layer (0-20 cm) of C. lanceolata + P. bournei multi-layered mixed plantations. The relationship between soil phosphorus fractions and soil microbial functional diversity was analyzed. The results showed that: (1) the contents of soil total phosphorus, available phosphorus, and inorganic phosphorus gradually increased with the increasing age of multi-layered mixed plantations. (2) the functional diversity of microbial communities showed great variations in different stands. Carbon metabolic activity and diversity index also increased with the increasing age of multi-layered mixed plantations. Major carbon sources which were utilized by soil microbes in C. lanceolata monoculture plantation were polymers. They were carbohydrates, carboxylic acids and phenolic acids in 7-year-old multi-layered mixed plantations, while more amino acids, amines, polymers, carboxylic acids and phenolic acids in 11-year-old multi-layered mixed plantations. In 11-year-old multi-layered mixed plantations, the utilization intensities of carbohydrates, amino acids, carboxylic acids, amines and phenolic acids were significantly higher than those in 4-year-old multi-layered mixed plantations and C. lanceolata monoculture plantation. The characteristics of carbon utilization of soil microbial communities showed little difference between 4-year-old multi-layered mixed plantations and C. lanceolata monoculture plantation (except polymers). (3) soil microbial diversity indexes, amino acids, amines and phenolic acids were significantly and positively correlated with soil total phosphorus, available phosphorus, Al-P and Fe-P content. Based on random forest model analysis, amino acids, amines and phenolic acids were the main carbon sources for soil microbial utilization in different stands. In summary, C. lanceolata monoculture plantations converted to multi-layered mixed plantations will be beneficial to the storage and supply of soil phosphorus. The metabolic functional diversity of soil microbial community may play a key role in regulating soil phosphorus availability in multi-layered mixed plantations.