ISWC OpenIR  > 水保所2018届毕业生论文
侵蚀环境中土壤微生物群落变化特征
孙棋棋
Subtype博士
Thesis Advisor郭胜利
2018-05-15
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline土壤学
Keyword土壤侵蚀 陡坡坡位 底土出露 植被措施 微生物群落
Abstract土壤微生物作为陆地生物圈的主要组分,驱动土壤有机碳矿化并调节土壤CO2通量,对土壤环境的变化有很强的敏感性。土壤微生物受到土壤温度、土壤水分和有机物质的深刻影响,而这些因素在侵蚀环境中发生强烈的分异。不同的侵蚀环境对土壤微生物的形成和稳定具有显著不同的影响,从而造成土壤微生物及其所调控的土壤碳动态截然不同的响应。加强不同侵蚀环境中土壤微生物的研究对准确理解和估算陆地生态系统CO2通量变化特征及其对变化环境的响应具有重要意义。
黄土区地形破碎,坡地分布广泛,土壤侵蚀强烈。径流和泥沙强烈地影响着侵蚀坡面土壤理化和微生物变化特征;侵蚀发生后发生土壤剖面倒转,出露的亚表土遗留在侵蚀区和沉积区的表面,使得原来掩埋在地下的土壤微生物曝露在自然环境中而发生强烈的变化;植被恢复措施也强烈地影响着水、热、泥沙、有机物在坡面的分布,进而影响着土壤微生物。本研究以长武站为依托,在典型侵蚀发生和治理的王东沟小流域内设置三个试验:1)径流小区试验:包括陡坡坡面上、中、下三个坡位,比较侵蚀坡面上不同坡位土壤微生物群落的变化特征;2)植被措施试验:比较侧柏林地和白羊草地两个半干旱区典型植被恢复措施对侵蚀坡面上土壤微生物群落的影响;3)模拟土层试验:比较对照和出露两个剖面,模拟底土出露对不同土层(表土:0–20 cm、亚表土:20–60 cm和深层土:60–100 cm)土壤微生物群落的影响。围绕土壤微生物开展以下三个方面的研究:1)描述不同侵蚀条件(陡坡坡位、植被措施及底土出露)下土壤微生物群落的变化特征;2)识别侵蚀条件下土壤微生物群落变化的影响因素;3)构建侵蚀环境中微生物群落与土壤呼吸的关联。测定指标包括土壤微生物多样性、群落组成、酶活性、土壤呼吸及其温度敏感性(Q10)、土壤碳氮组分、根系生物量和土壤温度、土壤水分等。
主要结果如下
1)细菌多样性在中坡位和下坡位显著高于上坡位,而真菌多样性在坡位间无显著差异。细菌β-变形菌纲(贫养菌)在中坡位和下坡位分别比上坡位减少25.3%和20.7%,而酸杆菌纲(富养菌)增加31.5%和35.8%。真菌群落组成由上坡位的以伞菌纲(贫养菌)为主(相对丰度23.7%)变为下坡位的以被孢霉目(富养菌)为主(相对丰度35.3%)。β-葡萄糖苷酶活性沿坡位向下降低,β-木糖苷酶和纤维二糖水解酶活性在中坡位提高,全部酶活性在下坡位最低。土壤水分、根系生物量及碳氮底物是坡位间土壤微生物群落差异的影响因素。
2)不同坡位细菌多样性(香农指数)在上坡位林地显著大于草地,在中坡位二者接近,在下坡位草地显著大于林地。草地变形菌门在各坡位均显著高于林地(15.0%,18.7%和9.7%);草地酸杆菌在上中坡位低于林地(31.1%和29.6%),而在下坡位无显著差异。β-葡萄糖苷酶活性在上坡位草地大于林地,而在中坡位和下坡位都表现为林地大于草地;纤维二糖水解酶活性在上坡位林草地一致,在中坡位草地大于林地,而在下坡位林地大于草地。土壤温度和碳氮底物是影响林草地之间土壤微生物群落差异的主要因素。
3)与原位相比,底土出露之后细菌群落主要表现为相对丰度的变化,真菌群落几乎无显著差异,且不同土层之间细菌群落的响应随土层深度而增加。出露土壤与原位土壤之间细菌群落组成在表层无显著差异;亚表土和深层土出露之后变形菌和放线菌内的富养群组增加,而贫养的热孢菌和硝化螺旋菌群组降低。细菌多样性在深层土显著增加,细菌群落结构在深层土达到差异显著。土层出露增加了亚表土β-木糖苷酶和纤维二糖水解酶活性和深层土β-葡萄糖苷酶活性。土壤矿质氮(亚表土)、矿质氮和DOC(深层土)是影响出露土壤和原位土壤间细菌群落组成差异的主要因素。
4)侵蚀坡面上沿着坡面向下,草地土壤呼吸显著增加了49.1%,Q10降低了13.2%。土壤呼吸与细菌丰富度和多样性呈显著正相关,而Q10与富养菌(酸杆菌纲、被孢霉目)负相关,与贫养菌(变形菌纲、伞菌目)正相关。侧柏林地和白羊草地虽然具有不同的侵蚀强度,但具有类似的呼吸和Q10。NO3-N与鞘氨醇单孢菌、芽球菌属、红色杆菌属呈正相关,且与Q10呈正相关;同时,NO3-N与红色杆菌属及纤维二糖水解酶活性呈正相关,且与草地土壤呼吸正相关,与Q10负相关。由于较少的微生物数量、较低的酶活性,底土出露之后的亚表土和深层土具有相对于表土显著降低的土壤呼吸(38.5%和33.9%)及Q10(21.8%和24.1%)。变形菌、放线菌、子囊菌中的富养菌群(芽球菌、微小杆菌和突脐蠕孢属、Pyrenochaetopsis属)直接与土壤呼吸和Q10正相关,而这些菌又都与参与碳循环的酶活性正相关。
 
主要结论:
1)陡坡不同坡位微生物群落组成由上坡位贫养菌为主转变为下坡位富养菌为主。相比侵蚀较弱的草地,较强侵蚀条件下林地微生物群落的空间变异较弱,富养菌更少,贫养菌更多。
2)相比真菌群落,细菌群落受土层出露的影响较大,这可能是由于真菌群落自身的内稳态机制。相比对照土壤,出露之后的土层具有更多的富养细菌,且侵蚀强度越大对微生物的影响越大。
3)通常富养微生物与较高的呼吸速率和较低的温度敏感性成正相关,而贫养微生物与较低的土壤呼吸速率和较高的温度敏感性成正相关。
上述结果对深入理解不同侵蚀环境下土壤微生物变化的影响机制以及准确估算区域CO2通量变化具有重要意义。
Other AbstractAs a key component of terrestrial biosphere, soil organisms drive the mineralization of soil organic carbon (SOC) and regulate soil CO2 efflux, being strongly sensitive to variation of soils. Soil microbial communities were profoundly affected by soil temperature, soil moisture and organic matter, which occur strongly differentiation in the environment of water erosion. Different types of erosion environment exert distinct effect on the formation and development of soil microbial communities, thus resulting in contrasting responses of soil microbial communities as well their regulated soil carbon dynamics. To research soil microbial communities under different environment erosion has critical significance in accurately understanding and estimating soil CO2 efflux of terrestrial ecosystem as well its response to altered environment.
The loess region has fragmented terrain and widespread sloping land where suffers severe soil erosion. Runoff and sediment strongly affected soil physicochemical and microbial properties along the eroded slopes. Soil profile inversion occurs when continued erosion of an upslope position transports material that originates from progressively deeper in the profile and layers it on top if previously deposited soils downslope. Ultimately, subsoils are left exposed at the surface in both eroded and depositional positions, thus bringing in large uncertainty to the soil microorganisms that residing in it. Vegetation restoration treatments also have strong effect on the distributions of soil water, heat, sediments, organic matter, thereby influencing soil microbial communities. Based on the the Changwu State Key Agro-ecological Experimental Station (shorten as Changwu Station), three field experiments were conducted at the typically managed Wangdonggou small watershed. 1) microbes-slope positions ex.: soil microbial community among slope positions (upper, middle and bottom slope positions) were compared along a sloping grassland; 2) microbes-vegetation ex.: soil microbial community between vegetation types (forest vs. grassland) were compared at various slope positions; 3) microbes-soil exposure ex. : soil microbial communities between the exposed and control soils were compared at various depths (topsoil: 0–20 cm, subsoil: 20–60 cm and deepsoil: 60–100 cm). During the experiment period from 2014 to 2016, the soil microbial community composition, activities of enzyme involved in soil carbon cycling, soil respiration and its temperature sensitivity (Q10), soil temperature, soil moisture, runoff, sediment, SOC, dissolved organic carbon, soil mineral nitrogen content and fine root biomass were measured. The aims of this study were to: 1) characterize soil microbial community composition and enzyme activities under different erosion environments (different slope positions, vegetation types and different depths of exposed soils); 2) identify the influencing factors of erosion environments on the soil microbial communities and enzyme activities; and 3) develop possible relationship between soil microbial community and soil respiration, Q10. The main conclusions were as follows:
1). Divergent responses of soil bacterial and fungal communities among slope positions were observed along the steeps slope. Soil bacterial diversity were greater at middle and bottom slope positions than at upper slope positions while fungal diversity varied little among slope positions. The bacterial class Betaproteobacteria was 25.3% and 20.7% lower but unidentified_Acidobacteria was 31.5% and 35.8% greater at bottom- than at upper- and middle- slope positions. The fungal community transitioned from being Agaricales-dominant (relative abundance of 23.7%) at upper slope position to being Mortierellales-dominant (relative abundance of 35.3%) at bottom slope position. The β-D-glucosidase activity generally declined down the slope while β-D-xylosidase and cellobiohydrolase activities hiked at middle slope position. All the enzyme activities were suppressed at bottom slope position. Soil water, root biomass and soil carbon/nitrogen content were the main factors affecting variation of soil microbial communities among slope positions.
2). Similar composition of soil microbial communities between forest and grassland revealed much stronger effect of soil types than that of vegetation types. However, vegetation exerted weak effect on soil bacterial community through different erosion intensities. The bacterial diversity of grassland was smaller, similar and greater than that of forest, respectively at upper, middle and bottom slope positions. The Proteobacteria was greater in grassland than in forest regardless of slope positions, while soil Acidobacteria was lower in grassland than in forest at upper and middle slope positions and similar between them at bottom slope position. The β-D-glucosidase activity was greater in grassland than in forest at upper slope position, and the cellobiohydrolase activity was greater in grassland than in forest at middle slope position, both of which were lower in grassland than in forest at bottom slope position. Soil temperature, soil carbon/nitrogen contents were the main factors influencing the variation of soil microbial communities between vegetation types at various slope positions.
3). Under the in situ condition, differences in the nutrients and organic matter among soil layers resulted in the enrichment of microbial biomass and enzyme activities, as well the variations of soil bacterial diversity and community composition. Moreover, soil bacterial community transitioned from being copiotrophs-dominant in the topsoil to being oligotrophs-dominant in the deepsoil. After being exposed, soils have similar microbial community composition with that of in situ, limited by the experimental time. However, subsoil exposure exerted effects on bacterial abundances, not fungal abundances. At both 20–60 and 60–100 cm, the copiotrophic groups within phyla Proteobacteria and Actinobacteria increased and the oligotrophic groups within phyla Thermotogae and Nitrospirae decreased in the exposed soil than in the control soil. Both number of species differentiated the two soils and magnitude of the increased abundances increased with depths. The increased soil mineral N (0–20 cm), soil mineral N (20–60 cm), soil mineral N and DOC (60–100 cm) were the factors controlling variation of bacterial community composition between the control and the exposed soils.
4). Contrasting distribution patterns of soil respiration and Q10 were observed along the steeps slope, with soil respiration increased by 49.1% and the Q10 decreased by 13.2% over the slope. Soil respiration positively correlated with bacterial diversity. The copiotrophic groups (unidentified_Acidobacteria and Mortierellales) negatively and oligotrophic groups (Betaproteobacteria and Agaricales) positively correlated with Q10. Although different vegetation types have equivalent soil respiration and Q10, different erosion intensities resulted in different pathway by which the soil microbial communities in grassland and forest involved in soil carbon cycling. As the only soil factors affecting the Q10 of forest, the NO3-N have postive effect on the Q10 through influencing the microbial communities involved in soil N cycling, such as Sphingomonas, Blastococcus and Rubrobacter. In contrast, the NO3-N have postive effect on the soil respiration and negative effect on the Q10 of grassland through influencing the microbial communities involved in soil N cycling, such as Rubrobacter. After being exposed, soils have the significantly decreased soil respiration and Q10 with increasing depths. That is, the subsoil and deepsoil have reduced soil respiration (by 38.5% and 33.9%) and Q10 (by 21.8% and 24.1%) relative to the topsoil, due to the limited microbial biomass and enzyme activities. Both soil respiration and Q10 have positive correlations with the copiotrophic groups within phyla Proteobacteria, Actinobacteria and Ascomycota (Blastococcus, Microvirga, Exserohilum and Pyrenochaetopsis), which at the same time positively correlated with all the microbial biomass and enzyme activities.
The main conclusions:
1)      The extremely strong spatial variation of soil microbial communities were revealed, as well as the difference between the responses of bacterial and fungal communities.
2)      The soil microbial communities were directly related to the soil respiration and its temperature sensitivity, thus providing evidence for the assumption that soil microbial driving soil carbon dynamics.
The findings in this study are of great importance to improve our understanding of the dynamics of soil carbon cycling in terrestrial ecosystem, so as to accurately estimate the variations of the soil CO2 flux of the erosion area.
Subject Area农学
Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8167
Collection水保所2018届毕业生论文
Affiliation1.中国科学院大学
Recommended Citation
GB/T 7714
孙棋棋. 侵蚀环境中土壤微生物群落变化特征[D]. 北京. 中国科学院研究生院,2018.
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