Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal.
Department of Biology, Mt. Allison University, Sackville E4L1G7, New Brunswick, Canada.
Sci Total Environ. 2021 Sep 1;785:147312. doi: 10.1016/j.scitotenv.2021.147312. Epub 2021 Apr 24.
The length and number of streams experiencing intermittency is expected to increase in response to human population growth, associated water use, and climate change. In these streams, habitat contraction may occur at distinct rates giving rise to drying periods of distinct duration. To date, the impact of drought installation rate and duration have been mostly overlooked. In this microcosm study, stream conditioned oak leaf litter was subjected to either a short (5 weeks) or a long (8 weeks) drying period, originating from a very slow, slow, or abrupt contraction. The effects of these treatments were compared at the end of the drying period in terms of microbial-mediated litter mass loss, fungal biomass, respiration, and sporulation rates. A very slow contraction pattern led to 1.3 times higher mass loss than both slow or abrupt contraction. Fungal biomass, respiration and sporulation rates were up to 2.3 times lower under slow than abrupt contraction. Both drying period durations inhibited leaf decomposition, suggesting an early, critical effect of drying on microbial-mediated processing, regardless of contraction pattern. This seems to be related to an impoverishment of leaf associated fungal communities and resultant lower functional efficacy - species richness decreased by up to 75% in response to a long (vs. short) drying period, despite the maintenance of mycelial biomass. Our results show the relevance of aquatic hyphomycetes to litter decomposition in dry streambeds, particularly following slower habitat contraction patterns. Faster wet-to-dry transitions and longer drying periods strongly impaired microbial functioning, with potential impacts on global processing rates and cascading effects through changes of detritus quality. If confirmed in field tests, such impacts on stream functioning may be mitigated by preserving riparian forests, which may protect against extreme drying events by buffering temperature changes.
预计随着人口增长、相关用水和气候变化，间歇性水流的长度和数量将会增加。在这些溪流中，栖息地的收缩可能以不同的速度发生，导致持续时间不同的干燥期。迄今为止，干旱安装率和持续时间的影响大多被忽视。在这个微观研究中，溪流条件下的橡树叶凋落物经历了短（5 周）或长（8 周）的干燥期，分别来自非常缓慢、缓慢或突然的收缩。在干燥期结束时，比较了这些处理的效果，包括微生物介导的凋落物质量损失、真菌生物量、呼吸和孢子形成率。非常缓慢的收缩模式导致质量损失比缓慢或突然收缩高 1.3 倍。与突然收缩相比，缓慢收缩下的真菌生物量、呼吸和孢子形成率低 2.3 倍。两种干燥期持续时间都抑制了叶片分解，这表明干燥对微生物介导的处理有早期的关键影响，而与收缩模式无关。这似乎与与叶片相关的真菌群落的贫化以及由此导致的功能效率降低有关——与短（长）干燥期相比，尽管维持了菌丝体生物量，物种丰富度下降了高达 75%。我们的结果表明水生真菌在干河床凋落物分解中的相关性，特别是在较缓慢的栖息地收缩模式下。更快的干湿交替和更长的干燥期强烈损害了微生物的功能，这可能对全球处理速率产生影响，并通过碎屑质量的变化产生级联效应。如果在野外测试中得到证实，通过保护河岸森林，可能会减轻对溪流功能的这种影响，河岸森林可以通过缓冲温度变化来防止极端干燥事件。
