桂西北喀斯特生态系统土壤微生物多样性及其影响因素

1、3ABSTRACT桂西北喀斯特生态系统土壤微生物多样性及其影响因素何 寻 阳专业：生态学指导老师：王克林 研究员摘 要桂西北喀斯特区脆弱而容量有限的资源环境与巨大的人口压力下，高强度的人为活动导致土地质量的下降与石漠化扩展。微生物群落是土壤重要的组成部分并是土壤质量变化的最早的预测指标。土壤中微生物多样性对维持土壤健康具有至关重要的作用，土壤生物的变化与生态系统的进化具有协同性。因此，研究植被演替与农业耕作措施对土壤微生物多样性及其功能的影响，对制订科学的恢复途径与耕作管理措施具有重要的理论和实践意义。本文利用野外调查与室内分析相结合的方法，研究不同土地利用方式对土壤微生物多样性及其功能的影响

2、，探讨土壤微生物的主要影响因素。主要的研究结果如下：随着喀斯特植被正向演替，土壤细菌代谢功能多样性与植物多样性变化趋势一致，而土壤细菌、真菌的遗传多样性没有明显变化规律；土壤微生物遗传多样性对季节响应更稳定：在演替早期阶段（草地），土壤细菌、真菌遗传多样性具有显著的季节变化，而且土壤真菌和细菌遗传多样性间具有显著的正相关关系。土壤细菌代谢模式及其多样性和真菌遗传多样性对喀斯特退耕模式响应更敏感，因此，利用土壤细菌代谢功能多样性及其代谢模式来评估土地利用方式改变对生态系统功能的影响及其生态后果具有重要的参考价值。土壤微生物对季节的响应比对退耕模式的响应更加敏感。在红壤丘陵移民安置区，与荒草地相比

3、，较短时期（6年）种植甘蔗或玉米-木薯农业耕作活动没有降低土壤微生物多样性，但改变土壤细菌代谢模式；马尾松林地土壤微生物的遗传和功能多样性最低，因此，在红壤地区选择针叶和阔叶混交适生种进行人工造林对于维持土壤微生物的可持续功能是必要的。土壤类型是影响土壤微生物多样性的关键因素。在旱季（12月），石灰土土壤细菌多样性显著高于红壤，而真菌多样性相反；石灰土微生物量碳氮都显著高于红壤。土壤pH、全氮、碳氮比和粘粒含量等是决定土壤微生物多样性的重要因子；尤其是土壤全氮含量，它是决定土壤微生物量的控制因子。农业耕作和管理方式（干扰）对土壤微生物产生重要的影响。这种影响主要是以耗竭土壤有机碳、氮等营养元素

4、而对土壤微生物发挥作用。土壤有机碳含量对土壤微生物量比对其多样性的影响更显著。关键词：土地利用，BIOLOG，PCR-DGGE，植被效应，季节变化Soil Microbial Diversity and Its Impacting Factors on Karst Ecosystems in Northwest Guangxi，ChinaHe Xun-yang (Ecology)Directed by Prof. Wang Ke-linABSTRACTThere are intensive contrasts between the frangible limited capability o

5、f natural environments and huge press of population and resources. The violent and unreasonable anthropogenic practices lead to ecological friability and continuous deterioration of rocky desertification. Soil microbial community is of important components and may be the earliest index for soil qual

6、ity assessment. It plays key role for soil microbial diversity to sustain soil healthy, and the changes of soil life-form cooperate with the evolution of ecosystem. There are crucially theoretic and practical values for taking reasonable restoration and management practices through investigating the

7、 effects of the degradation of vegetation and tillage on soil microbial diversity and its function. This study aims to survey different land-use type and to explore the influencing key factors on soil microbial diversity and its functions by combination field investigation and experimental analysis.

8、 The main results are as follows:Soil bacterial metabolic, but not taxonomic diversity can follow an increase in plant diversity. Moreover, we found evidence pointing towards an increased seasonal stability of soil taxonomic diversity over successional plant community development. Seasonal differenc

9、es in microbial taxonomic diversity were more often found in younger than older plant succession stages. Finally, our field survey showed that bacterial and fungal taxonomic diversity can be correlated. We conclude that apparent anthropogenic impacts on the integrity of plant community diversity may

10、 be paralleled by changes to the soil microbial community and that metabolic functioning of bacterial communities in disturbed environments (reflected by younger succession stages) may become less stable over the plant growth season.The bacterial community-level physiological profiling pattern (CLPP

11、), bacterial and fungal taxonomic diversities are sensitive to Grain-for-green models, which is very important worthiness for evaluating the changes of land-use and management on soil microbes and ecological sequels. More despondences with season than with Grain-for-green models for soil microbial c

12、ommunity were apparent. In hilly red soft immigrant region, northwest Guangxi province, comparing with tussock soil, the soil microbial diversities in crop land of sugarcane or maize/cassava did not reduce for short term reclamation (6 years), but the CLPPs were changed. There was the lowest microbi

13、al diversities in pine forest (Pinus massoniana), which clewed it was necessary for sustainability of soil microbial function to choose needle and broad mixed fitting plant species during artificial afforestation in red soil. Soil type was the key factor to affect microbial diversities. With opposit

14、ion to the fungal taxonomic diversity, the bacterial taxonomic diversity, microbial biomass carbon and nitrogen in lime soil were significantly higher then those in red soil in dry season, respectively. Soil pH, total nitrogen, the ratio of carbon and nitrogen (C/N) and clay were of the important ch

15、aracteristics determined the microbial diversities among soil phychemical properties, and especially the content of total nitrogen was the pivotal factor to control soil microbial biomass, according to partial correlation and path coefficient analyses.Tillage and management practices (disturbance) execute obvious influences on soil micr