暖化湿地土壤肌醇六磷酸酯动态消长特征及其微生物酶-功能基因驱动机理

Global climate change poses a complicated impact to the earth ecosystems; however, key issues on pathway of ecological 'source-sink' re-balance and the associated driving mechanisms in term of soil phosphorus (P) biogeochemistry in wetland ecosystem subjected to climate warming are still largely unknown. Six sites of wetlands within the delta area of Yiangzta River are selected to collect intact wetland columns due to their remarkably different P levels. Specifically aiming at inositol phosphates (InP, one of the most aboundent forms of soil organic P), a computerized warming microcosm filled with these wetland columns (since 2008) combined with a field warming mesocosm wetland are designed to investigate the soil InP dynamics and its fundmental molecular ecology mechanisms in wetlands subjected to 6-9 years-lasting experimental warming. The missions of this proposal are: (1) to identifiy and quantify the group of soil InP (including stereoisomers) over time in response to warming; (2) to explore the traits and roles of phytase-related enzymatic kinetics and thermodynamic bioreactions, and thereby to illustrate the direct force of InP dynamics; (3) to elucidate and quantify the temporal trends of InP-related microbe functional genes in soil by qPCR-mRNA molecular technology, deciphering the genetic force of soil InP dynamics in wetland subjected to warming. The goal of this proposal is to put light on regularities of InP dynamics and insights on the driving mechanisms of extracellular phytase integrated with microbe functional genes in soil of riparian wetland subjected to warming. The purpose of this proposal is to provide prospective and fundamental theory for P-related wetland ecosystem management coping with global warming.

气候暖化诱导的生态效应呈现复杂性。肌醇六磷酸酯是湿地土壤有机磷库的重要组分，此类磷素的消长显著影响着湿地土-水体系磷素分配的动态平衡，进而影响湿地本身及其下游水体的水质与生态功能。当前，暖化引起此类磷素动态消长规律、微生物酶特性变化以及功能基因响应与表达机理等尚无定论，而中-长期的演替行为更是知之甚少。本项目选取长三角区域磷库含量显著差异的6块湿地，采用暖化微宇宙(Microcosm，始于2008年)模拟与野外实证相结合的手段，1)揭示中-长期暖化（定位第6-9年）湿地土壤肌醇六磷酸酯及其特征性分子组分（含立体异构体）动态消长特征；2)阐明此类磷素消长的酶活性与降解动力学/热力学特性及其温度敏感性的动态演变趋势；3)应用qPCR-mRNA分子生态学技术，阐述与之相关的土壤微生物功能基因组演变及其表达的差异性规律。实施本项目可为暖化情景下实现内源磷素湿地土壤"汇功能"最大化调控提供理论依。

气候变化产生的生态效应呈现复杂性，暖化诱导湿地土壤磷素生物地球化学循环的“源-汇”演替方向、强度及其驱动机理等尚不清楚。本项目选取了长三角区域磷库显著差异的6块湿地，采用暖化湿地微宇宙(Microcosm)模拟的技术手段，针对有机磷（特别是肌醇六磷酸酯），开展中-长期暖化（连续定位第6-9年）土壤肌醇六磷酸酯动态消长及其分子生态学机理的研究。综合核磁共振（NMR）技术、16S高通量与集成基因芯片技术、以及生物信息计算技术，综合核磁共振（NMR）技术、16S高通量与集成基因芯片技术、以及生物信息计算技术，发现暖化生境湿地土壤微生物真菌群落显著增加，促进磷酯酶活性增强，细胞色素c基因（cytochrome c）和编码胞外多磷酸盐酶协同无机多磷酸盐降解功能基因（ppx）加快难降解磷素分解，从而导致土壤磷库向水体释放的强度加剧。与此同时，一氧化碳脱氢酶基因（CODH），乙酰辅酶A羧化酶基因（ppc）以及核酮糖-1，5-二磷酸羧化酶基因（rubisco）等功能基因的平衡作用加快主要是土壤稳定性碳库的降解。暖化作用下的湿地土壤磷素“源”的生态功能加强，其总磷及溶解性磷向水体释放的年均强度分别增长了12.94 mg cm-2 y-1 和 8.26 mg cm-2 y-1，这意味着当今气候暖化的发展趋势极有可能造成湿地（如湖泊、水库、河流等水源地）富营养化程度的加剧与安全水源有效供给的降低，因此需要我们从区域宏观层面上提出前瞻性的应对策略。暖化土壤微生物对碳库（淀粉、半纤维素、几丁质以及木质素等）的利用效率呈现增加趋势，多酚氧化酶以及过氧化物酶的潜在活性显著提高，最终导致湿地土壤稳定性碳库的损失，这种变化趋势说明暖化不利于湿地土壤自身碳库的保持，而碳库的损失又反过来加剧气候暖化。综上，主要从基因组学角度阐明了暖化湿地土壤“涉磷-涉碳”功能基因组动态演替规律，丰富了区域与全球尺度下健康生态构建的冲击应对理论，可为应对气候暖化冲击并科学调控湿地水生态提供理论依据。