荒漠化草原土壤漆酶基因多样性及微生物群落结构研究

Microorganisms are highly involved in the mineralization of soil organic matters (SOM), acting as the active participants in the nutrients recycling and energy flow of the ecosystems. Lignin is one of the most abundant biopolymer in SOM and is also the most difficult to degrade. Lignin biodegradation has important effects on soil quality and SOM turnover. Laccase is one of the key enzymes of lignin biodegradation, occupying an important position in nature carbon cycle. Being linked to the ecological process of litter decomposition, laccase is widely used in the study of soil microbial diversity in recent years. In ecosystems, both the functional gene diversity and the community structure of microorganisms are significantly affected by different vegetation types. The desert steppe is an important part of ecosystems in our country. The SOM content of desert steppe soil, which plays a direct role in ecological evolution of the desertification regions, is very low. The desert steppe nearby the xixia tomb is chosen as the research object in this project. Based on the determination of the physiochemical properties of different desert soils, the effects of different vegetation types on the diversity of laccase gene and the structure of microbial community was comparatively studied to explore the relationship between the laccase-containing microorganism communities and the ecological factors resulting from vegetation types. The results will help to clarify the carbon cycle from litters to soil and the driving mechanism by microorganisms in the desert ecosystem. The research will provide theoretical guidance for the soil remediation of the desert steppe.

土壤中的微生物承担着生态系统中90%以上有机质的矿化作用，是生物元素循环和能量流动的积极参与者。木质素是土壤有机质的重要组成部分，也是其中最难降解的成分，木质素降解对土壤质量和有机质转换具有重要影响。漆酶是降解木质素的关键酶之一，与凋落物降解紧密相关，在碳素循环中占有重要的地位，被广泛用于土壤微生物多样性的研究。生态系统中，不同植被类型能够导致分解有机质的微生物功能基因多样性和群落结构产生差异。荒漠化草原在我国占有重要的地位，荒漠土有机质含量少，对荒漠化地区的生态演化有直接的影响。本项目选取荒漠生态系统中西夏王陵遗址附近荒漠草原为研究对象，在测定不同土壤样品理化性质的基础上，比较研究具有不同植被类型的荒漠土壤的漆酶基因多样性、微生物多样性与群落结构特征，以期为全面深入研究荒漠生态系统植物向土壤归还有机质的碳循环过程以及相应的微生物驱动机制提供基础数据，为荒漠化草原的土壤修复提供理论指导。

荒漠化草原在我国占有重要的地位，土壤有机质对荒漠化地区的生态演化有直接的影响。本项目选择了荒漠化草原上七种典型的植物群落，采集植物土壤及相应裸地土壤作为研究材料，在测定土壤理化性质及酶活性的基础上，研究细菌漆酶基因多样性和土壤的微生物群落结构，分离纯化产漆酶的细菌并对其进行鉴定。七种植物均能增加土壤酶活性，但对土壤养分的富集作用有较大差异，其中，贺兰山丁香、灰榆、松叶猪毛菜对土壤养分的改良效果最佳，是七种植物群落中较为理想的类型；土壤酶活性与各理化性质间存在一定的关联，植物能促使土壤酶活性与各理化性质间的关系更加密切，使土壤酶与有机质等营养成分都具有显著正相关关系，其中速效钾和有机质是影响土壤酶活性的最重要因素。不同植物对土壤微生物的丰富度、多样性及群落结构的影响差异较大，斑子麻黄和鹰爪柴使细菌丰富度显著增加，斑子麻黄使真菌丰富度显著增加；松叶猪毛菜使细菌和真菌的多样性显著增加，蒙古扁桃、斑子麻黄和鹰爪柴使细菌多样性显著增加。子囊菌、接合菌、担子菌均为优势真菌，放线菌、变形菌、酸杆菌、芽单胞菌为优势细菌，七种荒漠植物均使放线菌减少。荒漠土壤中含漆酶基因的细菌分布于14个门中，以变形菌门、放线菌门、厚壁菌门为优势类群，荒漠植物能够改变产漆酶细菌的丰富度和多样性，使可培养的产漆酶微生物数量增加，种类更丰富。综上，植物凋落物增加了荒漠土壤有机质，富集芽孢杆菌属、鞘氨醇单胞菌属等功能微生物群，影响功能微生物的分布，从而改变微生物群落结构与丰富度、多样性，提高土壤酶活性，加快土壤中碳、氮、磷元素的循环。荒漠化草原土壤中有机质的生物降解是以变形菌、放线菌、厚壁菌等细菌为主导的过程。