Koranda Marianne, Kaiser Christina, Fuchslueger Lucia, Kitzler Barbara, Sessitsch Angela, Zechmeister-Boltenstern Sophie, Richter Andreas
Department of Terrestrial Ecosystem Research, University of Vienna, Althanstr. 14, 1090 Vienna, Austria.
Soil Biol Biochem. 2013 May;60(100):95-104. doi: 10.1016/j.soilbio.2013.01.025.
Substrate quality and the availability of nutrients are major factors controlling microbial decomposition processes in soils. Seasonal alteration in resource availability, which is driven by plants via belowground C allocation, nutrient uptake and litter fall, also exerts effects on soil microbial community composition. Here we investigate if seasonal and experimentally induced changes in microbial community composition lead to alterations in functional properties of microbial communities and thus microbial processes. Beech forest soils characterized by three distinct microbial communities (winter and summer community, and summer community from a tree girdling plot, in which belowground carbon allocation was interrupted) were incubated with different C-labeled substrates with or without inorganic N supply and analyzed for substrate use and various microbial processes. Our results clearly demonstrate that the three investigated microbial communities differed in their functional response to addition of various substrates. The winter communities revealed a higher capacity for degradation of complex C substrates (cellulose, plant cell walls) than the summer communities, indicated by enhanced cellulase activities and reduced mineralization of soil organic matter. In contrast, utilization of labile C sources (glucose) was lower in winter than in summer, demonstrating that summer and winter community were adapted to the availability of different substrates. The saprotrophic community established in girdled plots exhibited a significantly higher utilization of complex C substrates than the more plant root associated community in control plots if additional nitrogen was provided. In this study we were able to demonstrate experimentally that variation in resource availability as well as seasonality in temperate forest soils cause a seasonal variation in functional properties of soil microorganisms, which is due to shifts in community structure and physiological adaptations of microbial communities to altered resource supply.
底物质量和养分有效性是控制土壤中微生物分解过程的主要因素。由植物通过地下碳分配、养分吸收和凋落物分解驱动的资源有效性的季节性变化，也会对土壤微生物群落组成产生影响。在这里，我们研究微生物群落组成的季节性变化和实验诱导变化是否会导致微生物群落功能特性的改变，进而影响微生物过程。以三种不同微生物群落为特征的山毛榉森林土壤（冬季和夏季群落，以及来自环剥树木地块的夏季群落，其中地下碳分配被中断），在添加或不添加无机氮的情况下，与不同的碳标记底物一起进行培养，并分析底物利用情况和各种微生物过程。我们的结果清楚地表明，所研究的三个微生物群落在对添加各种底物的功能反应上存在差异。冬季群落对复杂碳底物（纤维素、植物细胞壁）的降解能力高于夏季群落，这表现为纤维素酶活性增强和土壤有机质矿化减少。相反，冬季对易分解碳源（葡萄糖）的利用率低于夏季，这表明夏季和冬季群落适应了不同底物的有效性。如果提供额外的氮，在环剥地块中建立的腐生群落对复杂碳底物的利用率显著高于对照地块中与植物根系关联更强的群落。在本研究中，我们能够通过实验证明，温带森林土壤中资源有效性的变化以及季节性会导致土壤微生物功能特性的季节性变化，这是由于群落结构的变化以及微生物群落对资源供应改变的生理适应所致。
