丹江口库区退耕还林下微生物周转土壤有机磷特征及潜在的环境效应

Microbiological transformation of soil organic phosphorus is the current focus of soil science and ecology. However, there are few reports about the mechanisms and environmental effects of microbiological transformation of soil organic phosphorus under afforestation, possibly due to the diversity of microbial community structure and the complexity of soil phosphorus transformations. By using technologies such as solution 31P NMR, phosphate oxygen isotope and soil enzymology, based on soil phosphorus adsorption-desorption characteristics and soil phosphorus sorption index, in this project, we will explore the chemical nature of soil organic phosphorus, microbial activity and community structure, microbiological transformation of soil organic phosphorus and the related environmental effects in soil aggregates under afforestation ecosystems (cropland, shrubland and woodland) in Danjiangkou Reservoir area. This effects and mechanisms of microbiological transformation on soil phosphorus retention, transformation and loss under different afforestation ecosystems will be revealed through this project, which will provide available data support for optimal soil phosphorus management in Danjiangkou Reservoir area.

土壤微生物对磷素转化的过程及机制是当前土壤学和生态学关注的焦点问题。然而，退耕还林下，由于微生物群落结构的多变性以及土壤磷转化过程的复杂性，关于土壤微生物转化磷过程、机制及环境行为的研究仍鲜有报道。本研究拟以丹江口库区退耕还林生态系统（农田、灌丛和森林）为研究对象，应用液体31P核磁共振技术、磷酸盐氧同位素技术、土壤磷脂脂肪酸技术、土壤酶学等方法，并结合土壤磷吸附-解吸动力学参数及土壤磷吸持指数等指标，对退耕还林不同植被类型下土壤团聚体中有机磷的化学组成、微生物活性及群落结构、微生物转化有机磷过程及其环境效应进行研究；以期揭示退耕还林下微生物调控的土壤磷周转过程对土壤磷保持、转化及流失的影响及机制，为库区土壤磷素优化管理提供参考依据。

本研究以丹江口库区30年的退耕还林生态系统（裸地、农田、灌丛和林地）为研究对象，对不同土地利用类型下土壤团聚体中C、N、P的含量、组成、δ13C和δ15N同位素值、微生物群落结构（PLFA）和C、N、P相关水解酶活性进行测定。此外，还利用土壤元素和酶计量方法分析了土壤N、P储存与供应与对应C过程的关系，阐明土地利用变化下土壤P丰缺状况的潜在环境效益。本研究的主要结果与结论如下：.原土和土壤团聚体中总P含量沿着土地利用类型的变化没有明显的改变，土壤酸性和碱性磷酸单酯酶、总PLFA、在造林地土壤中显著高于裸地和农田。土壤SOC:TP和TN:TP在造林地中显著低于裸地和农田；虽然总体上P水解相关的酶与C和N相关的酶呈显著的正相关关系，但造林地中C:P和N:P酶计量显著低于农田，与元素计量比的变化一起，表明在造林地中P素相对更缺乏。相关和随机森林的结果表明，在不同粒级中影响C:P和N:P酶计量的因子不同，在大团聚体中微生物因子对C:P和N:P的解释量小于小团聚体，表明在大团聚体中团聚体粒级的阻隔使得微生物元素需求和资源获取之间存在障碍，加剧了大团聚体中P的限制。