岩溶区固氮植物引种的土壤磷素活化效应及其微生物机制研究

Phosphorus availability is a key limiting factor for vegetation restoration due to high calcium content and pH in karst shrub ecosystems, and thus phosphorus mobilization is more important in the limestone soil. Phosphorus mobilization is influenced by nitrogen-fixing plants, which can improve phosphorus availability through increasing the activity of root secretion and microbial. However, the mechanism of the phosphorus mobilization through plant root exudates and microbes of nitrogen-fixing plants is poorly understood. In this study, nitrogen-fixing plants from the karst shrub ecosystem are cultivated to investigate the effects of root exudates of nitrogen-fixing plants on the soil phosphorus mobilization and plant phosphorus absorption by pot experiment. The real-time PCR and Miseq high-throughput sequencing will be applied to explore the effect of abundance and community structure of functional microbes from nitrogen-fixing plant rhizosphere soils on the soil phosphorus mobilization and plant phosphorus absorption. Microbial activity inhibition technique will be used to quantify the contribution of plant root exudates and the organic phosphorus mineralization of microbes to the mobilization and transformation of soil phosphorus in the karst limestone soil. This project will reveal the mechanisms of the cultivated nitrogen-fixing plants affecting phosphorus mobilization and transformation through plant root exudates and microbes in the karst limestone soil. The results of this study will provide a scientific basis for the reduction of vegetation restoration barriers, and guiding ecological recovery of degraded karst ecosystems.

受高钙与pH影响，岩溶石灰土对磷素吸附强烈，磷素有效性成为限制岩溶区灌丛植被恢复的主要障碍因子，对其活化是提高植物磷素利用率的关键。磷素活化受氮素输入的影响，固氮植物能够提高根系分泌和微生物活性，促进磷有效性和磷循环，但岩溶区固氮植物磷活化效应的根系分泌物和微生物驱动机制的认识还非常有限。本项目拟以岩溶灌丛生态系统中固氮植物为研究对象，通过盆栽试验，探讨固氮植物根系分泌物对土壤磷素活化及植物磷素吸收的影响；采用实时荧光PCR与Miseq高通量测序技术，探讨固氮植物根际微生物对土壤磷素活化及植物磷素吸收的影响；结合微生物活性抑制技术，量化固氮植物根系分泌物与微生物对岩溶石灰土磷素活化转化的贡献；阐明岩溶区固氮植物引种的土壤磷素活化效应及其微生物驱动机制。研究结果可为岩溶区灌丛植物恢复障碍因子消减和退化生态系统可持续恢复提供理论支撑。

受高钙与pH影响，岩溶石灰土对磷素吸附强烈，磷素有效性成为限制岩溶区灌丛植被恢复的主要障碍因子，对其活化是提高植物磷素利用率的关键。磷素活化受氮素输入的影响，固氮植物能够提高根系分泌和微生物活性，促进磷有效性和磷循环，但岩溶区固氮植物磷活化效应的根系分泌物和微生物驱动机制的认识还非常有限。本项目拟以岩溶灌丛生态系统中固氮植物为研究对象，通过野外调查、室内环境因子分析及控制实验等方式研究固氮植物根系分泌物与根际微生物对岩溶石灰土磷素活化转化的影响。研究结果表明：固氮植物引种（香合欢与木豆）显著提高土壤磷素有效性，不同豆科植物活化磷量不同，无论是灌木林与乔木林阶段土壤，均表现为木豆活化磷量高于香合欢。同一豆科植物，灌木林阶段土壤活化的磷量高于乔木林阶段土壤活化的磷量。采用微生物活性抑制技术，发现不同阶段，植物与微生物对土壤有效磷活化的贡献率不大一样。灌木林阶段，植物活化的磷量高于根际微生物，而乔木林阶段，植物活化的磷量低于微生物。生长在灌木林阶段土壤中的2种固氮植物根系菌根侵染率显著高于乔木林阶段，表明植被恢复初期，植物通过自身活化磷素能够满足生长，随着植被的恢复（后期），植物对磷素的需求量增大，微生物活化磷素将是植物获取磷素养分的重要策略。植被恢复初期，植物主要依靠共生微生物（丛枝菌根真菌）为其提供磷素养分，植被恢复后期，植物主要依靠土壤中游离的磷素转化功能微生物为其提供磷素养分；从磷素养分活化角度，优先考虑选择C.cajan（木豆）应用于岩溶区植被恢复。该项目为岩溶区植物恢复障碍因子消减、退化生态系统可持续恢复提供理论依据。