【作者】 田晓堃；

【导师】 王鹏程； 林英华；

【作者基本信息】 华中农业大学 ， 水土保持与荒漠化防治， 2010， 硕士

【摘要】 土壤微生物在土壤生态系统中扮演着重要角色。然而,由于其个体尺寸的显微性、数量的庞大性、种类的多样性、时空分布的变异性和影响因素的复杂性,土壤微生物及其与环境的关系一直是微生物生态学研究的难点问题。近年来,生态系统中地下部分与地上部分关系研究已成为生态学研究的热点问题,因此,揭示土壤微生物地理学分布规律及其与环境因子关系对于准确评价土壤微生物在生态系统中的维持功能显得重要而且有意义。本论文以长江三峡库区两种典型的植被类型杉木马尾松混交林和马尾松纯林为研究对象。在林分尺度上,采用平板稀释方法结合16SrDNA和Biolog鉴定技术,对土壤可培养细菌的数量和多样性进行了比较分析；在此基础上,利用简单相关分析、线性回归分析、典范对应分析(CCA)方法对土壤细菌各大类群数量和细菌多样性与环境因子的关系进行了研究；最后,运用地统计学方法研究了土壤细菌的时空异质性规律以及土壤细菌与其环境影响因子的空间结构的相关性。获得以下研究结论：1.土壤可培养微生物数量：两种植被类型下不同季节三大类群土壤微生物的数量的大小关系均为：细菌>放线菌>真菌,其中,土壤细菌数量在2.475×106cfu/g-3.675×106cfu/g之间,放线菌数量1.031×106cfu/g～1.635×106cfu/g之间,真菌数量在4.836×104cfu/g～11.880×104cfu/g之间；相同季节马尾松林三大类群微生物数量均高于杉木马尾松混交林,且除细菌和秋季真菌外差异性显著。杉木马尾松林中,春季土壤细菌和真菌数量低于秋季,放线菌数量略高于秋季,但它们差异性不显著。马尾松纯林中春季土壤细菌和放线菌高于秋季,真菌数量低于秋季,差异性同样不显著。植被类型是引起土壤微生物数量差异的主要因素,而春、秋两季变化对微生物数量的差异影响不显著。2.土壤可培养细菌的群落组成：杉木马尾松混交林中春季主要的细菌类群及比例为：假单胞菌(Pseudomonas),69.86%、伯克霍尔德氏菌(Burkholderia),1.97%、芽孢杆菌(Bacillus),14.39%;秋季：假单胞菌,50.56%、伯克霍尔德氏菌,16.29%、芽孢杆菌,14.82%、溶杆菌(Lysobacter),1.95%、不动杆菌(Acinetobacter),0.52%、金黄杆菌(Chryseobacterium),2.81%，马尾松纯林中春季主要的细菌类群及比例为：假单胞菌,66.02%、伯克霍尔德氏菌,13.45%、假杆菌属(Flavobacterium),0.04%、芽孢杆菌,10.10%；秋季：假单胞菌,49.22%、伯克霍尔德氏菌,8.42%、克雷伯氏菌(Klebsiella),4.73%、金黄杆菌,1.86%、微球菌(Micrococcus),0.11%、芽孢杆菌,16.48%。两种植被类型的细菌群落组成有一定的区别。秋季细菌种类增加,但增加的几种细菌数量较少,同一植被类型季节间主要细菌类群比较相似。3.土壤可培养细菌多样性：春季两种植被类型4个多样性指数没有差异,秋季除了Pielou均匀度指数外,马尾松混交林其余多样性指数显著的高于杉木马尾松混交林。不同季节下,两种植被类型土壤细菌多样性指数的变化不同；杉木马尾松林中：除了Margalef丰富度指数外,秋季多样性指数均高于春季。马尾松林中,秋季4个多样性指数均高于春季。土壤可培养细菌的多样性受到季节和植被类型同时作用。与地上植被乔、灌、草3层的多样性比较表明地下土壤细菌的多样性在植被类型间的变化与地上植被正好相反。4.土壤细菌和土壤理化性质的相关性：杉木马尾松林土壤有机质、全氮、碳氮比、含水量和pH值均显著的高于马尾松纯林；绝大多数土壤细菌与土壤理化性质的相关性不显著。典范对应分析(CCA)的结果表明,CCA排序结果很好的解释了土壤细菌和本研究选取的5个土壤理化性质因子的关系,两种植被类型下CCA前两个排序轴的解释量分别高达90.40%和81.70%。表明土壤细菌受到理化性质因子的共同作用。5.土壤细菌与森林结构因子的回归分析：杉木马尾松林中,平均胸径(AverageDBH)与土壤细菌的线性相关性最强。其中,又以4.00m范围内平均胸径(AverageDBH(4))与土壤细菌的线性相关最为普遍,它与假单胞菌、伯克霍尔德氏菌、溶杆菌、蜡状芽孢杆菌数量和细菌总数以及Shanon-Wiener多样性指数构成显著的一元线性回归方程。马尾松纯林中,平均胸径和最大胸径(Max DBH)两个森林结构因子进入线性回归方程,分别是6.00m范围内平均胸径(Average DBH (6))、5.00m范围内平均胸径(Average DBH (5))和8.00m、7.00m、4.00m、3.00m范围内最大胸径(Max DBH (8)、Max DBH (7)、Max DBH (4)、Max DBH (3)),其中。以Average DBH (6)与土壤细菌的线性相关性最为普遍,它分别与假单胞菌、芽孢杆菌、蜡状芽孢杆菌数量、其他未鉴定土壤细菌数量和细菌总数以及Shanon-Wiener多样性指数构成显著的一元线性回归方程。典范对应分析(CCA)的结果表明,CCA排序结果很好的解释了土壤细菌和加入森林结构因子后的环境因子的关系,两种植被类型下CCA前两个排序轴的解释量有所下降,分别为83.4%和77.1%。6.地统计学空间异质性分析：在林分尺度上,半方差函数分析和克里格插值表明两种植被类型土壤细菌存在明显的空间结构和时空异质性。其空间自相关范围为51.00m。两种植被类型土壤细菌的空间异质性在不同方向上和尺度上,存在明显的区别。即土壤细菌空间变异存在各向异性。两种植被类型下与X轴呈45°和135°两个方向的土壤细菌的各向异性比在春、秋两季变化趋势相似。土壤细菌的时空变异不受土壤细菌数量和多样性季节变化的影响。7.土壤细菌与环境因子的空间变异的关系：地统计学的分析结果表明土壤细菌和与其紧密联系的土壤理化性质和森林结构这些环境因子存在明显相似的空间结构。它们之间的半方差函数平均值存在极显著相关性。土壤细菌不仅数量、多样性与环境因子紧密联系,其空间结构的形成也由这些环境因子的空间异质性引起。更多还原

【Abstract】 Soil microbes play an important role in soil ecosystem system. However, the research of interrelationship between soil microbes and the environment has been one of the tough issues in microbial ecology field, due to the microscopic size of the individual, mass quantities, soil microbial diversity, the variability of space-time distribution, and the complexity of the influence factors. The correlation between above-ground and under-ground parts in ecological system is a hotspot in the current field of ecology research. Therefore, it’s important and meaningful to reveal the laws of soil geographic distribution and interrrelationship with environmental factors, in order to give an accurate assessment of the soil microbes’role in maintaining the functions of the ecosystem.In this paper, two typical vegetation types (the Chinese-fir and Masson-pine mixed forests and the Masson-pine pure forests) in three gorges reservoir area were chosen to carry out this research work. In the scale of standing forest, using dilution-plate method combining 16SrDNA sequence analysis and Biolog identification technology, the number and diversity of the bacterium which soil can nurture were compared and analised; On this basis, using simple correlation analysis, the linear regression analysis, and canonical correspondence analysis (CCA) method, the relationship between the major groups of soil bacteria and bacterial diversity with the environmental factors were studied; Finally, geostatistics was used for analyzing the space-time heterogeneous distribution of the soil bacteria and the correlation with the spatial structure of the environmental impact factors. Conclusions are as follows:1.The quantity of culturable soil microbes:Under two vegetation types mentioned above and different seasons conditions, the quantity of the three major soil microbes groups sorted by size always are:bacteria> actinomycetes> fungi, in which the quantity of bacteria is 2.475×106cfu/g～3.675×106cfu/g, actinomycetes1.031×106cfu/g 1.635×106cfu/g, fungi 4.836×104cfu/g～11.88×104cfu/g; Quantities of the three types are all higher in pine forests than in mixed fir-pine forests in different seasons, in addition, exclude of bacteria and fungi in autumn there are significant differences. Fir-pine forests has less soil bacteria and fungi but slightly more actinomycetes in spring than in fall, and there are not significant differences. In pure pine forests, the quantities of bacteria and actinomycetes in spring are higher than in fall, spring fungi below autumn, also no significant difference. Vegetation type is the main reason lead to quantity variance of the soil microbes and that there are no significant differences between spring and fall seasons.2.The community composition of culturable soil bacteria:The main bacteria groups and their proportions in spring fir-pine mixed forests are:Pseudomonas 69.86%, Burkholderia 1.97%, Bacillus 14.39%; In autumn fir-pine mixed forests are: Pseudomonas 50.56%, Burkholderia 16.29%, Bacillus 14.82%, Lysobacter 1.95%, Acinetobacter 0.52%, Chryseobacterium 2.81%. The main bacteria groups and their proportions in spring pure pine forests are:Pseudomonas,66.02%, Burkholderia,13.45%, Flavobacterium 0.04%, Bacillus,10.10%; In autumn pure pine forests are:Pseudomonas, 49.22%, Burkholderia,8.42%, Klebsiella 4.73%, Chryseobacterium 1.86%, Micrococcus 0.11%, Bacillus subtilis,16.48%. The community composition of soil bacteria is varied between different vegetation types. There are more bacterial species in autumn than spring, and those new types are with relatively low quantities, for the same vegetation type there are not much difference in the major soil bacteria species despite different seasons.3.The diversity of culturable soil bacteria:There is no significant difference between the 4 diversity indexs of the soil bacteria under two kinds of forests in spring, but indexs except Pielou are significantly higher in pine forests than that of fir-pine mixed forests in the fall. The indexmovement varied under different seasons for both vegetation types. Exclude Margalef index, other diversity indexs are all higher for fir-pine mixed forests in autumn than spring. In pine forests, all 4 diversity indexs are higher in the fall. The diversity of culturable soil bacteria is effected by both season and vegetation type. Compared with the diversity of above ground Arbor-Bush-Grass layers vary from vegetation types, the change of diversity of soil bacteria proves the contrary.4.The correlation between soil bacteria and soil properties:The content of soil organic matter, total nitrogen, carbon nitrogen ratio, moisture content and PH value are all significantly higher in fir-pine mixed forests than pure pine forests. The overwhelming majority of the correlations between soil bacteria and soil properties are not significant. Canonical Correlation Analysis(CCA) ordination well demonstrated the relationship between soil bacteria and the 5 soil properties selected for this research, the first two axises explained as high as 90.4% and 81.7% separately for two vegetation types.5.The regression analysis between soil bacteria and forest structure factors:Among those factors Average DBH (diameter at breast height) has the strongest linear correlation with soil bacteria in fir-pine mixed forests, moreover, soil bacteria is commonest relevant with Average DBH within 4.00m, Average DBH (4) together with quantities of Pseudomonas, Burkholderia, Dissolving bacteria, Bacillus cereus and total bacteria and the diversity index of Shanon-Wiener constitute a significant linear regression equation. In pure pine forests, Average DBH and Max DBH were entered in the equation of linear regression,separately with Average DBH (6), Average DBH (5), and Max DBH (8), Max DBH (7), Max DBH (4), Max DBH (3), among all this the Average DBH(6) had most significant linear correlation with soil bacteria, it together with quantities of Pseudomonas, Bacillus, Bacillus cereus, other unidentified bacteria and total bacteria, and the diversity index of Shanon-Wiener constitute a significant linear regression equation. Canonical Correlation Analysis(CCA) ordination well demonstrated the relationship between soil bacteria and the environmental factors added with forest structure factors, the correctly explained volume of the first two axises slightly dropped, accounted for 87.4% and 77.1% separately for two vegetation types.6.The analyse of spatial heterogeneity based on geostatistics method:On the forest stand scale, the results of semivariance analysis and kriging interpolation showed significant spacestructure and space-time heterogeneity for soil bacteria under two vegetation types. The range of spatial autocorrelation is 51.00m. Spatial heterogeneity obviously differs from directions and scales for soil bacteria under two vegetation types, thus spatial variation of soil bacteria shows remarkable anisotropy. The variation trend of the soil bacteria anisotropy ratio between the two directions of X-axis 45°and 135°is nearly the same in spring and autumn season under the two kinds forests. The space-time heterogeneity of soil bacteria is independent of the seasonal variation in quantity and diversity. 7.The relationship of spatial variation between soil bacteria and environmental factors:Results of geostatistical analysis showed that the spatial structure of soil bacteria is very similar to that of environmental factors including their closely interrelated soil properties and forest structure factors. There is very significant correlation between their average semivariograms. Not only the quantity and diversity of soil bacteria closely related to environment factors but also the spacial structure formed by spatial heterogeneity of environmental factors.更多还原