特定微域系统漆酶功能菌群时序特征及其对木质素和多酚矿化的影响

This proposal aims to investigate the laccase correlated microorganisms and the processes of decomposition of lignin, polyphenol and soil organic carbon, and their temporal characteristics responding to different ecological factors. A microcosm incubation will be carried out with three forest soils including the alpine tundra, coniferous and broad-leaved forest in Changbai Moutain. Forest litters collected in the above three forests will be used as exogenous substrates for soil incubation. The incubation temperatures will be separately set at 5, 15 and 25 ℃. Therefore, three factor and multi-level lab incubation experiment will be carried out to investigate the effects of forest soil types, temperature and litter qualities on laccase correlated microorganisms and the degradation of soil recalcitrant organics matter. At given times, (RT-)PCR and DGGE will be applied to analyze laccase genes' diversity, and the acquired cDNA sequences will be compared with the known laccase genes and their taxa will be confirmed. Phospholipid fatty acid and amino sugar contents will also be measured to clarify the specific microbial community compositions' alteration over time. Laccase activities, CO2 emission rates, lignin and polyphenol contents will be also measured to determine the carbon mineralization rates of recalcitrant substances in microcosms, and also, through two exponential models, the decomposition kinetics of lignin and polyphenol and soil organic carbon in the microcosm will be described over incubation time. Through the multi-way ANOVA, the effects of forest ecosystem soil types, temperatures and plant litter qualities and their interaction on the above microbial biomarkers and carbon mineralization parameters will be determined, and the correlation between the above biomarkers and indicators will be analyzed by multiple linear regression. This proposal will address the knowledge of responding realistic and effective ecological functions involving in the key metabolic pathway of soil organic matter mineralization in different forests under global climate change.

针对温度、凋落物种类（质量）、森林土壤类型对特定组分矿化过程的影响及相关功能菌群的响应机制的科学问题，提出利用三因素多水平室内微域培养，并以木质素和多酚组分矿化过程及漆酶功能菌群时序特征为研究对象，可明确局限条件下SOC矿化关键步骤对不同生态因子的响应规律。微域培养不同时期，提取土壤DNA与RNA，进行（RT-)PCR-DGGE，探索真菌和细菌漆酶基因多样性、表达水平、种属分类特征；测定磷脂脂肪酸与氨基糖含量，明确漆酶功菌群的指纹特征；检测木质素与多酚含量、土壤呼吸速率、漆酶活力，借助双室模型定量描述木质素、多酚、总SOC矿化动力学特征。利用多因素方差分析和多元线性回归等手段，阐明各组分矿化潜势、速率常数与漆酶功能菌群组成、活力的相关关系，以及二者对温度、凋落物、森林土壤类型等生态因子的响应机制，对揭示漆酶功能菌群对森林SOC矿化调控机制、完善陆生系统碳排放对气候变化响应的认识有重要意义。

针对温度设置（恒温与变温）、林分条件（针叶林与落叶林）以及土壤层次（O层与A层）等环境因素对特定碳组分矿化过程及相关功能菌群组成及多样性影响的科学问题，提出利用三因素多水平室内微域培养，并以木质素和多酚组分等有机碳（SOC）矿化过程及包括漆酶功能菌群在内的真菌、细菌微生物群落时序特征为研究对象，明确局限条件下SOC矿化对不同生态因子的响应规律。研究结果表明，不同培养时期土壤瞬时呼吸速率、碳矿化过程动力学参数、水溶性碳、木质素与多酚、磷脂脂肪酸与氨基糖、真（细）菌及漆酶功能菌群多样性等指标均受恒-变温、林分条件和土壤层次显著影响。总体上，不同有机碳库矿化速率、包括漆酶功能菌群在内的土壤真菌和细菌菌群活力等指标，随温度变化呈现低温处理最低，恒高居中，变温处理最高；它们于恒温处理条件下的温度敏感性显著低于变温处理。应对恒-变温不同温度设置，微生物群落明显进化出两种生存策略：即富营养型与贫营养型。碳矿化过程与菌群的温度敏感性回归分析表明，富营养型菌群显著与碳矿化温度敏感性正相关，二者形成正反馈；贫营养菌则与碳矿化过程温度敏感性负相关，二者形成负反馈。林分条件显著影响碳矿化速率和难分解碳组分（如多酚、木质素等）分解过程的温度敏感性，落叶林影响大于针叶林；对真菌、细菌和漆酶功能菌群温度敏感性的影响表现为落叶林小于针叶林。不同土壤层次亦显著影响上述指标的温度敏感性，真（细）菌多样性、木质素C单体、多酚、冷水溶性碳等温度敏感性表现为O层>A层；而漆酶活力与相关功能菌群、木质素V单体等表现为O层<A层。本研究对揭示微生物群落对森林SOC矿化调控机制、完善陆生系统碳排放对气候变化响应的认识有重要意义。

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