Changes in soil carbon pools and microbial activity along land-use gradients in grassland and forest ecosystems

微生物是土壤中的主要分解者，其活动对土壤碳储量有很大影响。胞外酶在土壤有机质矿化中起着重要作用。虽然土壤中几乎所有的碳都是可降解的，但土壤中相当一部分碳不容易被微生物获取，它们的生长往往受到可用能量或营养来源的限制。特别是基质对粘土颗粒的吸附似乎降低了它们对微生物的可利用性。土地利用和环境变化影响了进入土壤的新基质的数量和组成，以及游离和矿物相关组分之间的碳分布。这也会影响微生物活动和酶的产生，进而影响土壤碳储量。虽然在实地研究中很难确定土壤碳的微小变化，但特定酶活性的变化可以作为变化的早期指标。该项目的目的是将微生物组成和活动与受土地利用影响的主要勘探地点的土壤碳储量联系起来。我们打算分析不同年龄的粒度组分的碳储量和对土地利用变化的敏感性，以及这些组分中一系列细胞外酶的活性。酶活性是功能性土壤生物多样性的一个指标，与物种多样性和酶编码基因分析结果密切相关。

Microorganisms are the main decomposers in the soil and their activity strongly affects soil carbon storage. Extracellular enzymes play an important role in the mineralization of soil organic matter. While almost all carbon in soils is potentially degradable, a considerable part of carbon in soils is not easily accessible to microbes and their growth is often limited by available energy or nutrient sources. Especially the sorption of substrates to soil particles of the clay fraction seems to reduce their availability to microorganisms. Land use and environmental changes affect the amount and composition of new substrates entering the soil as well as the distribution of carbon between free and mineral associated fractions. This also influences microbial activity and enzyme production, which in turn affects soil carbon storage. While small changes in soil carbon are hard to identify in field studies, shifts in the activities of specific enzymes can be early indicators for changes. The aim of this project is to link microbial composition and activity to soil carbon storage as affected by land use on the main sites of the exploratories. We intent to analyse carbon storage in particle size fractions of different age and sensitivity to land use changes as well as the activities of a range of extracellular enzymes in those fractions. Enzyme activities are an indicator for functional soil biodiversity and will be related to results about species diversity and enzyme encoding gene analyses.