鄱阳湖植被群落演替过程中土壤有机碳的变化及微生物响应机制

Wetland, as an important carbon pool, containing 10 percent of the total C in the global terrestrial ecosystem, plays a key role of "switcher" in holding and releasing of greenhouse gases, such as CO2 and CH4. Content of soil organic carbon and its composition and structure are important parameters for evaluating soil carbon storage or release,and also microbial community is the most active part in soils, and plays the 'biological pump' of soil carbon cycle in ecosystem, and keeps the balance of carbon in the wetland ecosystem by linking the aboveground (plant communities) and underground (soil environment). Nanjishan Nature Reserve site of Poyang Lake was selected for this project, and variation of soil organic C,the composition and structure of soil oarganic C in soil and plant, and soil microbial characters were carried out under the succession process of typical wetland in Poyang Lake. By analyzing correlation between soil organic C, structure and the active component of soil organic C in soil and plant, plant community biomass, soil microbial structural diversity, and carbon sequestration microbial functional group at the wetland, variation of soil organic carbon and its stabilization mechanism at the wetland would be revealed. Theoretical guidance would be supplied for further understanding soil carbon cycle, for optimizing ecology of wetland, even for making a basic decision to response the climate warming caused by excessive carbon emissions in the Poyang Lake.

湿地是陆地生态系统的重要碳库，约占全球陆地生态系统碳库的10%，在CO2和CH4等温室气体的固定和释放中起着重要的"开关"作用。土壤有机碳活性组分和结构是评价土壤碳储存与释放的重要参数。微生物群落是土壤中最具活力的部分，是生态系统土壤碳循环的"转换机"，与地上植被和地下环境相互作用、互为因果，共同承载着湿地生态系统碳元素的平衡。本项目拟选择鄱阳湖南矶山自然保护区为试验点，分析湿地演替过程中土壤有机碳、植被和土壤有机碳的化学结构和活性组分、土壤微生物特征研究，探讨土壤有机碳组分和结构、植被、土壤微生物之间的相关性，揭示鄱阳湖流域湿地演替过程中土壤有机碳的变化及其稳定机制，为了解鄱阳湖湿地土壤碳循环，优化鄱阳湖湿地的生态，应对过量碳排放导致的气候变暖问题提供理论指导和决策依据。

土壤碳循环在湿地生态系统中非常重要，微生物对土壤有机碳的利用和转化决定着碳周转过程。本项目利用光谱学和高通量测序技术，分析鄱阳湖湿地植被演替过程中土壤有机碳及其化学结构和活性组分变化，土壤微生物群落结构特征及其与它们之间的关系，研究发现：.不同植被群落下(芦苇 Phragmites australis (Cav.) Trin. ex Steud-LW、南荻Triarrhena lutarioriparia L. Liou-ND、苔草Carex cinerascens-TC和茭白Zizania latifolia (Griseb) Stapf-JB，裸滩地作为对照-DZ)，土壤理化性质，酶活性、有机碳活性及结构组分，及微生物结构多样性变化趋势没有一致性。土壤Rubisco酶活差异显著（P<0.05），依次表现为TC＞LW＞ND＞JB＞DZ＞TL，说明植被类型对土壤酶活具有重要的影响。cbbl基因与16s rRNA比值表现为ND＞TL≥JB＞TC＞LW＞DZ，在微生物中含cbbl基因的固碳微生物所占比值在裸滩地最低，说明ND和TL的固碳功能微生物表现更为活跃。通过Mi-seq高通量测序发现，不同植被群落下土壤微生物群落结构多样性（OTU、Ace、Chao、Shannon指数）差异不显著，而群落组成丰度差异显著：如变形菌门、酸杆菌门、硝化螺旋菌门等。.不同水位（枯水期、平水期和丰水期）对土壤理化性质、土壤酶活性、土壤微生物群落和结构多样性的影响表现出重要的影响。如不同水位时期土壤温度差异显著；土壤过氧化氢酶酶、脲酶和蔗糖酶活性也有显著差异（P<0.05），土壤活性有机碳和可溶性有机碳含量差异显著（P<0.05）。烷基类除外，土壤有机质的结构组成差异显著(P < 0.05)。平水期对土壤羧化酶酶活有促进作用，枯水期对酶活有抑制作用。.相关性分析表明， pH和酸杆菌门、Ignavibacteriae、厚壁菌门呈显著正相关，说明这些微生物适合在酸性或弱酸性条件下生长。土壤有机质（SOM）和酸杆菌门正相关，活性有机碳（AOC）、可溶性有机碳（SOC）、SOM和硝化螺旋菌门负相关，AOC和拟杆菌门、Ignavibacteriae、螺旋菌门显著或极显著正相关，SOC和Ignavibacteriae极显著正相关。硝化螺旋菌门和烯烃，芳香类，碳水化合物类，酚醇类正相关，和烷烃类负相关。