1、桂西北喀斯特生態系統土壤微生物多樣性及其影響因素何 尋 陽專業：生態學指導老師：王克林 研究員摘 要桂西北喀斯特區脆弱而容量有限的資源環境與巨大的人口壓力下，高強度的人為活動導致土地質量的下降與石漠化擴展。微生物群落是土壤重要的組成部分并是土壤質量變化的最早的預測指標。土壤中微生物多樣性對維持土壤健康具有至關重要的作用，土壤生物的變化與生態系統的進化具有協同性。因此，研究植被演替與農業耕作措施對土壤微生物多樣性及其功能的影響，對制訂科學的恢復途徑與耕作管理措施具有重要的理論和實踐意義。本文利用野外調查與室內分析相結合的方法，研究不同土地利用方式對土壤微生物多樣性及其功能的影響，探討土壤微生物的

2、主要影響因素。主要的研究結果如下：隨著喀斯特植被正向演替，土壤細菌代謝功能多樣性與植物多樣性變化趨勢一致，而土壤細菌、真菌的遺傳多樣性沒有明顯變化規律；土壤微生物遺傳多樣性對季節響應更穩定：在演替早期階段（草地），土壤細菌、真菌遺傳多樣性具有顯著的季節變化，而且土壤真菌和細菌遺傳多樣性間具有顯著的正相關關系。土壤細菌代謝模式及其多樣性和真菌遺傳多樣性對喀斯特退耕模式響應更敏感，因此，利用土壤細菌代謝功能多樣性及其代謝模式來評估土地利用方式改變對生態系統功能的影響及其生態后果具有重要的參考價值。土壤微生物對季節的響應比對退耕模式的響應更加敏感。在紅壤丘陵移民安置區，與荒草地相比，較短時期（6年）

3、種植甘蔗或玉米-木薯農業耕作活動沒有降低土壤微生物多樣性，但改變土壤細菌代謝模式；馬尾松林地土壤微生物的遺傳和功能多樣性最低，因此，在紅壤地區選擇針葉和闊葉混交適生種進行人工造林對于維持土壤微生物的可持續功能是必要的。土壤類型是影響土壤微生物多樣性的關鍵因素。在旱季（12月），石灰土土壤細菌多樣性顯著高于紅壤，而真菌多樣性相反；石灰土微生物量碳氮都顯著高于紅壤。土壤pH、全氮、碳氮比和粘粒含量等是決定土壤微生物多樣性的重要因子；尤其是土壤全氮含量，它是決定土壤微生物量的控制因子。農業耕作和管理方式（干擾）對土壤微生物產生重要的影響。這種影響主要是以耗竭土壤有機碳、氮等營養元素而對土壤微生物發揮

4、作用。土壤有機碳含量對土壤微生物量比對其多樣性的影響更顯著。關鍵詞：土地利用，BIOLOG，PCR-DGGE，植被效應，季節變化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 of natural

5、 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 quality asses

6、sment. 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 effects

7、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. The main

8、 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 differences in mic

9、robial 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 be paral

10、leled 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), bacter

11、ial 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 community

12、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 microbial divers

13、ities 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 opposition to th

14、e 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 characteris

15、tics 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