Effects of stoichiometry and temperature perturbations on beech leaf litter decomposition, enzyme activities and protein expression

[摘要] Microbes are major players in leaf litter decomposition and thereforeadvances in the understanding of their control on element cycling are ofparamount importance. Our aim was to investigate the influence of leaflitter stoichiometry in terms of carbon (C) : nitrogen (N) : phosphorus (P)ratios on the decomposition processes and to track changes in microbialcommunity structures and functions in response to temperature stresstreatments. To elucidate how the stoichiometry of beech leaf litter (Fagus sylvatica L.) and stresstreatments interactively affect the microbial decomposition processes, aterrestrial microcosm experiment was conducted. Beech litter from differentAustrian sites covering C:N ratios from 39 to 61 and C:P ratios from 666 to1729 were incubated at 15 °C and 60% moisture for six months.Part of the microcosms were then subjected to severe changes in temperature(+30 °C and −15 °C) to monitor the influence oftemperature stress. Extracellular enzyme activities were assayed andrespiratory activities measured. A semi-quantitative metaproteomics approach(1D-SDS PAGE combined with liquid chromatography and tandem massspectrometry; unique spectral counting) was employed to investigate theimpact of the applied stress treatments in dependency of litterstoichiometry on structure and function of the decomposing community. Inlitter with narrow C:nutrient (C:N, C:P) ratios, microbial decomposers weremost abundant. Cellulase, chitinase, phosphatase and protease activitydecreased after heat and freezing treatments. Decomposer communities andspecific functions varied with site, i.e. stoichiometry. The applied stresscombined with the respective time of sampling evoked changes of enzymeactivities and litter pH. Freezing treatments resulted in a decline inresidual plant litter material and increased fungal abundance, indicatingslightly accelerated decomposition. Overall, a strong effect of litterstoichiometry on microbial community structures and functions was detected,but decomposition was mainly driven by a combination of the investigatedfactors. Temperature perturbations resulted in short- to medium-termalterations of microbial functions; especially high temperature treatmentsblocked decomposing enzymes.

[学科分类] 地球化学与岩石