Knowledge Resource Center for Ecological Environment in Arid Area
| Ecological gradients caused by land-use change and land management alter soil microbial biomass and community functioning in a tropical mountain rainforest region of southern Ecuador | |
| Tischer;Alexander | |
| 出版年 | 2016 |
| 学位授予单位 | Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden |
| 英文摘要 | Global change phenomena, such as forest disturbance and land-use change significantly affect elemental balances as well as the structure and function of terrestrial ecosystems. Inappropriate land management often causes nutrient losses and finally soil degradation and loss of soil functioning. Especially in tropical ecoregions, soil degradation by nutrient losses is widely abundant. Soil microorganisms are the proximate agents of many processes performed in soils and are regarded as sensitive bio-indicators. However, the incorporation of microbial responses to the definition of critical soil conditions is not intensively developed. In the present thesis, several data analyses of the relationships between ecosystem disturbance and land-use change (natural forest, pastures of different ages, secondary succession) and a diverse set of soil ecological characteristics in the tropical mountain rainforest region of southern Ecuador were compiled. In particular, it was tested whether soil microbial biomass and community functioning were sensitive to land-use change effects. Furthermore, an information-theoretic approach was applied to find the factors that regulate soil microbial biomass and community function. Finally, in a nutrient enrichment experiment the above- and belowground responses to N and P additions were examined. The tested research questions and results were linked to the theory of ecological stoichiometry in order to connect the research to a sound and unifying scientific basis. Soil and microbial stoichiometry were affected by both land-use change and soil depth. After forest disturbance, significant decreases of soil C:N:P ratios at the pastures were fol-lowed by increases during secondary succession. Microbial C:N ratios varied slightly in response to land-use change, whereas no fixed microbial C:P and N:P ratios were observed. Shifts in microbial community composition were associated with soil and microbial stoichiometry. Strong positive relationships between PLFA-markers 18:2n6,9c (saprotrophic fungi) and 20:4 (animals) and negative associations between 20:4 and microbial N:P point to land-use change affecting the structure of soil food webs. Significant deviations from global soil and microbial C:N:P ratios indicated a major force of land-use change to alter stoichiometric relationships and to structure biological systems. Data analysis reveals a strong impact of land-use change on soil microbial biomass, C-mineralization, gross-NH4-consumption and –production rates. According to the results of the IT-approach, combined models better describe effects of land-use change on soil microorganisms than single explanation models. Microbial resources and soil chemical environment were important pre-dictors for soil microbial biomass and community functioning. Little is known about the environmental drivers of the catalytic properties of EHEs (e.g., pH, nutrients) and their functional link to the structure of soil microbial communities. The activities of the six hydrolytic enzymes were tested. Microbial production of AP responded to the low P status of the sites by a higher investment in the acquisition of P compared to C. Three major drivers of enzyme activities were found to be significant for enzyme production: 1.) Microbial demand for P regulated the production of AP, provided that N and C were available. At the natural forest site the two-fold higher specific activity of AP pointed to a high microbial P-demand, whereas the production of AP was constrained by the availability of N and DOC after pasture abandonment. 2.) Microbial biomass that was controlled by pH and resource availability was the main driver for CBH, BG and NAG activities. 3.) Substrate induction due to increased litter inputs of herbaceous plant species seemed to regulate AG and XYL activities during secondary succession. The enzymes’ affinity to substrate, as a potentially critically enzyme kinetic parameter is understudied. The data analysis suggest |
| 英文关键词 | ?kosystemzerst?rung ?kologische St?chiometrie Enzymaktivit?ten Enzymkinetiken Mikrobielle Biomasse N?hrstoffanreicherung N?hrstofffreisetzung PLFA Seriell-verbundene N?hrstoffe Boden Ecosystem distrubance Ecological stoichiometry Enzyme activities Enzyme kinetics Microbial biomassn Nutrient enrichment Nutrient mineralization PLFA Serially linked nutrients Soil Ddc:630 Rvk:ZC 73588 Rvk:ZC 72400 |
| 语种 | 英语 |
| URL | http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-190211 |
| 来源机构 | Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/250287 |
| 推荐引用方式 GB/T 7714 | Tischer;Alexander. Ecological gradients caused by land-use change and land management alter soil microbial biomass and community functioning in a tropical mountain rainforest region of southern Ecuador[D]. Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden,2016. |
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