| 题名 | 岷江上游干旱河谷灌丛群落土壤胞外酶活性分布特征研究 |
| 作者 | 王冰冰 |
| 学位类别 | 硕士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 曲来叶 |
| 关键词 | 岷江干旱河谷 土壤水分有效性 “灌丛沃岛”效应 土壤胞外酶活性 生态酶活性化学计量 Semi-arid Minjiang River valley soil water availability “shrub island” effect soil extracellular enzyme activities ecoenzymatic stoichiometry |
| 其他题名 | The distribution patterns of soil extracellular enzyme activities of shrubs in the semi-arid upper Minjiang River valley |
| 学位专业 | 生态学 |
| 中文摘要 | 土壤胞外酶是土壤有机质分解的主要介质，其活性常与微生物代谢速率、养分的生物化学循环联系起来。与碳(C)、氮(N)和磷(P)分解矿化相关的土壤胞外酶（生态酶）的相对活性可以揭示微生物生长和代谢的元素化学计量和能量限制。全球干旱生态系统占据陆地表面的41 %，承载着35.5 %的人口，但恶劣而脆弱的生态环境使其极易受到全球变化的影响。岷江干旱河谷地区，水土流失严重，植被覆盖度低。尽管目前已有许多研究关注了该区域，但多以地上植物为主，且缺乏对土壤胞外酶活性的研究，特别是缺乏在水分梯度和植被异质性背景下探讨影响土壤胞外酶活性变异的因素，以及相关的物质循环。 本研究，选取了岷江上游干旱河谷沿岸4个存在水分差异的灌丛群落样地，调查了灌丛组成、灌丛下和空地中土壤理化性质、微生物群落组成和4种胞外酶活性，探讨影响岷江干旱河谷土壤胞外酶活性及生态酶活性化学计量变异的主要因子、灌丛 “沃岛效应”与水分梯度之间的关系、以及从酶活性的角度探讨影响微生物生长代谢的潜在限制性因子。结论如下： （1）土壤水分有效性（土壤含水量）是驱动岷江干旱河谷区域土壤胞外酶活性和生态酶活性化学计量变异的主要因子，是影响该地区养分循环的最重要因素。“灌丛沃岛”对土壤物理化学性质、微生物生物量和群落组成以及土壤胞外酶活性的影响，受到水分有效性的调控。 （2）土壤微生物，特别是真菌和菌根真菌类群对土壤胞外酶活性变异的作用在更为干旱的样地和环境条件相对更为恶劣的空地土壤中更为突出，且由于其与C、P酶活性表现的正相关性，反映了它们在干旱生态系统养分循环，特别是C、P循环中的重要作用。 （3）岷江干旱河谷区域土壤C:N:P酶活性化学计量约为3:2:3，表现出与全球1:1:1尺度的相对特异性。总体上，该区域土壤微生物生长代谢或许存在一定的N限制，并且这种限制在更为干旱的样地中表现的更为突出，而在相对湿润的样地中则表现为一定的P限制。这种样地之间的差异性，同样体现了土壤水分有效性的调控作用。 （4）灌丛与空地之间相对较小的差异，以及不同样地间灌丛与空地生态酶活性化学计量特征的相似性，说明了灌丛与空地在养分循环上的相似性，从而“灌丛沃岛”有可能是生态恢复的基础。 |
| 英文摘要 | Soil extracellular enzymes are prominent agent for the decomposition of soil organic matter. The activities of these enzymes are commonly related to the metabolic rate of microbial communities and carbon and nutrient cycling. The relative activities of carbon (C), nitrogen (N) and phosphorus (P) related extracellular enzymes (i.e. ecoenzymatic ratios) can reveal the stoichiometric and energetic constrains of microbial metabolism and growth. Dryland ecosystems cover about 41 % of global land surface and support nearly 35.5 % of the world’s population, yet we know little about the factors that drive the variation of soil extracellular enzymes involving in C and nutrient cycling, especially in the semi-arid Minjiang River valley, where the ecological processes can be constrained by low water availability and vegetation patchiness. We selected four shrub communities under different water gradients along the upper Minjiang River valley to investigate the variation of soil physicochemical properties, microbial biomass and community composition (phospholipid fatty acid biomarkers), and four enzyme activities related to C, N and P cycling under the shrubs and in the shrub interspaces (gaps). The main objectives were to determine the main factors affecting the variation of soil extracellular enzyme activities and ecoenzymatic stoichiometry and the potential nutrient limitation of microbial community metabolism as revealed by ecoenzymatic stoichiometry. The shrub “island of fertility” effect on soil properties under the background of soil water gradients was also discussed. There were several conclusions concluded by this study as follows: (1) Soil water availability (Soil water content) was the most important driving force for determining the distribution patterns of soil extracellular enzyme activities and ecoenzymatic stoichiometry in the semi-arid River valley, and was thus the main factor for nutrient cycling. The effects of “shrub islands” on soil physiochemical properties, microbial biomass and composition, and soil extracellular enzyme activities were also mediated by soil water availability. (2) The effects of soil microbial community, especially fungi or arbuscular mycorrhizal fungi (AMF), on the variation of enzyme activities were more critical in the relatively drier sites and the shrub interspace soils with relatively worse soil environmental conditions. And the positive correlation between fungi (AMF) and C and P related enzyme activities suggested their indispensable role in the C and P cycling of this dryland. (3) The pattern of ecoenzymatic stoichiometry of C:N:P was about 3:2:3 in the semi-arid Minjiang River valley, which was relatively special as compared to the 1:1:1 scaling ratio of the global pattern. Overall, there may be some degree of nitrogen limitation of microbial metabolism across the valley. This limitation can be even more prominent in the relatively drier sites, while in the relatively wetter sites, the microbial metabolism was more constrained by P availability. This difference between sites was also regulated by the effect of soil water availability. (4) The relatively small differences between the shrub and shrub interspace soils and the similarity of ecoenzymatic stoichiometry pattern in the shrub or in interspace soils across sites both indicated that the two type of soils had similar nutrient cycling patterns, and therefore “shrub island” could be the basis of ecological restoration. |
| 公开日期 | 2015-07-07 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/15710]  |
| 专题 | 生态环境研究中心_城市与区域生态国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 王冰冰. 岷江上游干旱河谷灌丛群落土壤胞外酶活性分布特征研究[D]. 北京. 中国科学院研究生院. 2014. |
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