土壤无机碳微生物转化过程及其对石漠化强度响应机制

Soil plays a decisive role in the global carbon balance. However, very little attention was focused on the research of karstification and carbon transfer in the Karst area, especially on the role of microbes in soil inorganic carbon transformation and migration. The research object is land use (forests, shrubs, grassland, farmland, abandoned land) and corresponding degraded ecosystems of rocky desertification in rocky desertification area. The key of the research was soil microbial biomass, activity and community structure and soil inorganic carbon transfer and migration by field investigation, the fixed-point observation and experimental research methods, and its aim was to clarify the effect of soil microbial respiration activity and fungi/metabolism of bacteria and community characteristics influence on balance of soil CaCO3 dissolution and precipitation. The other key of the research was quantity and components of water soluble organic materials in the process of decomposition of plant residues, and the role of water soluble organic materials in soil inorganic carbon transfer and migration, and its aim was to clarify the influence of microbial metabolites on inorganic carbon. Based on the above, the research was to comprehensively study on soil inorganic carbon storage and distribution in different intensity of rocky desertification and the relationship between soil microbial biomass and community structure, reveal the transformation processes of soil microbes to inorganic carbon and mechanism of response to karst rocky desertification.

土壤无机碳在全球碳平衡中具有举足轻重的作用，而其与微生物作用的研究尚未得到广泛关注，特别是岩溶土无机碳转化方面的研究极为薄弱。本研究以岩溶山区不同土地利用方式（林地、灌丛、草地、农田、撂荒地）对应的石漠化生态系统为对象，采用野外调查-实地取样-室内模拟-试验分析相结合的方法，系统分析土壤微生物生物量碳、真菌生物量、细菌生物量、微生物群落代谢图谱、水溶性有机物含量、无机碳等指标，阐明土壤微生物呼吸强度、细菌与真菌的数量和活性及群落代谢特性对土壤碳酸钙溶解的影响；分析土壤微生物分解植物残体过程中产生的水溶性有机物的数量和组成，以及其对溶液中Ca2+、HCO3-和CaCO3沉淀的关系，阐明微生物代谢产物对土壤碳酸钙淋移与淀积的影响；结合野外监测和室内模拟，综合分析表层土壤无机碳的贮藏量与分布以及与土壤微生物生物量及其群落结构之间的关系，揭示土壤无机碳微生物转化过程及其对石漠化强度响应机制。

项目在全面考察贵州石漠化生态系统对应的土地利用类型基础上，选取典型土地利用类型样地（农田、草地、灌丛、林地），系统分析了石漠化生态系统下土壤有机质输入对土壤环境特征（理化性质、酶活性、微生物群落）和无机碳分布的影响、无机碳添加对土壤有机碳和微生物群落特征的影响以及土壤无机碳的贮量与土壤环境特征因子之间的关系，初步阐明了石漠化生态系统土壤无机碳的固持与微生物转化过程。主要研究成果：（1）土地利用方式通过改变枯落物的物理和化学组成，显著影响土壤有机质的输入，进而显著改变了土壤理化性质。（2）土地利用方式显著改变了土壤碳酸酐酶活性，土壤碳酸酐酶活性表现出农田>草地>灌丛>林地；土地利用方式显著改变了土壤细菌和真菌群落的多样性指数，农田土壤细菌群落的Chao1、Simpson、Shannon、Pielou、Observed_species、Faith指数较高；灌木林地土壤真菌群落的Chao1和Observed_species指数较高，而农田土壤真菌群落的Simpson、Shannon 和Pielou指数较高。（3）土地利用方式显著改变了表层（0-10cm）土壤无机碳含量与密度分布，表现为灌丛>草地>林地>农田；土壤无机碳δ13C含量表现为：0-10 cm土层，草地和灌丛显著高于耕地和林地；10-20 cm和20-30 cm土层耕地和草地显著高于灌丛和林地。（4）不同土地利用方式下添加无机碳对土壤TOC、活性碳和惰性碳含量在无机碳添加8d、16d、24d后无显著改变，但农田土壤总无机碳含量在添加无机碳后24d 显著低于8d；添加无机碳对土壤细菌群落的Chao1、Shannon、Observed_species和Faith显著不同，而添加无机碳对土壤真菌群落多样性无显著影响。（5）土壤无机碳的贮量与土壤环境特征因子相关性表明，土壤理化性质显著影响土壤无机碳贮量，土壤酶、土壤真菌对土壤无机碳贮量无显著影响，土壤某些细菌（如B__Firmicutes正向影响无机碳贮量）而不是多样性对土壤无机碳贮量有影响。整体研究结果表明石漠化显著改变了土壤理化性质、土壤酶和微生物组成，而中度石漠化（灌丛）有利于土壤无机碳的固持。