Stream Ecology Laboratory, Department of Plant Biology and Ecology, Faculty of Science and Technology, University of the Basque Country, UPV/EHU, Bilbao, Spain.
MARE-Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal.
Microb Ecol. 2021 Nov;82(4):897-908. doi: 10.1007/s00248-021-01858-w. Epub 2021 Sep 27.
Litter decomposition is an ecological process of key importance for forest headwater stream functioning, with repercussions for the global carbon cycle. The process is directly and indirectly mediated by microbial decomposers, mostly aquatic hyphomycetes, and influenced by environmental and biological factors such as water temperature and litter quality. These two factors are forecasted to change globally within the next few decades, in ways that may have contrasting effects on microbial-induced litter decomposition: while warming is expected to enhance microbial performance, the reduction in litter quality due to increased atmospheric carbon dioxide and community composition alteration may have the opposite outcome. We explored this issue through a microcosm experiment focused on early microbial-mediated litter decomposition under stream oligotrophic conditions, by simultaneously manipulating water temperature (10 °C and 15 °C) and litter quality (12 broadleaf plant species classified into 4 categories based on initial concentrations of nitrogen and tannins). We assessed potential changes in microbial-mediated litter decomposition and the performance of fungal decomposers (i.e., microbial respiration, biomass accrual, and sporulation rate) and species richness. We found stronger effects of litter quality, which enhanced the performance of microbial decomposers and decomposition rates, than temperature, which barely influenced any of the studied variables. Our results suggest that poorer litter quality associated with global change will have a major repercussion on stream ecosystem functioning.
凋落物分解是森林集水区功能至关重要的生态过程，对全球碳循环有影响。该过程直接和间接受到微生物分解者的介导，主要是水生真菌，受环境和生物因素的影响，如水温及凋落物质量。这两个因素预计在未来几十年内会在全球范围内发生变化，可能会对微生物诱导的凋落物分解产生相反的影响：虽然升温预计会提高微生物的性能，但由于大气二氧化碳增加和群落组成改变导致的凋落物质量下降可能会产生相反的结果。我们通过一个微宇宙实验来探索这个问题，该实验专注于在集水区贫营养条件下早期的微生物介导的凋落物分解，同时操纵水温（10°C 和 15°C）和凋落物质量（12 种阔叶植物物种，根据氮和单宁的初始浓度分为 4 类）。我们评估了微生物介导的凋落物分解和真菌分解者（即微生物呼吸、生物量积累和孢子形成率）以及物种丰富度的潜在变化。我们发现凋落物质量的影响更强，它增强了微生物分解者的性能和分解速率，而温度几乎没有影响任何研究变量。我们的结果表明，与全球变化相关的较差的凋落物质量将对集水区生态系统功能产生重大影响。
