Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
GRECO, Institute of Aquatic Ecology, University of Girona, Campus de Montilivi, 17071 Girona, Spain.
Environ Microbiol Rep. 2017 Dec;9(6):756-765. doi: 10.1111/1758-2229.12592. Epub 2017 Oct 13.
A consequence of drought in streams is the emersion of decomposing leaf litter, which may alter organic matter recycling. We assessed the effects of emersion on decomposition of black poplar leaves and associated microbes (microbial biomass, extracellular enzyme activities and microbial diversity) in two streams with distinct characteristics, in particular nutrients, temperature and oxygen levels. Leaf decomposition rates, fungal biomass and extracellular enzyme activities were lower in the most impacted stream (high nutrients and temperature, low oxygen). Also, the structure of fungal and bacterial communities differed between streams. Emersion strongly affected all microbial functional measures. Leaf decomposition, fungal biomass and extracellular enzyme activities were more sensitive at the most pristine site, while fungal reproduction and bacterial biomass production were more affected by emersion at the most impacted stream. Microbial community structure was strongly altered after emersion. Although similar effects on leaf-associated microbes were found in both streams, functional responses to emersion differed probably as a consequence of different initial microbial communities with different sensitivity to the drying stress. Our study highlights the need of understanding the effects of drought in streams suffering from different environmental perturbations, since responses to emersion appear to depend on the environmental context.
干旱会导致溪流中分解的落叶暴露出来，这可能会改变有机物质的循环。我们评估了在两个具有不同特征（特别是营养物质、温度和氧气水平）的溪流中暴露对黑杨树叶分解及其相关微生物（微生物生物量、胞外酶活性和微生物多样性）的影响。在受影响最大的溪流（高营养和高温、低氧）中，落叶分解率、真菌生物量和胞外酶活性较低。此外，溪流之间的真菌和细菌群落结构也不同。暴露强烈影响所有微生物功能指标。在最原始的地点，叶片分解、真菌生物量和胞外酶活性的敏感性更高，而在受影响最大的溪流中，真菌繁殖和细菌生物量的产生受暴露的影响更大。微生物群落结构在暴露后发生了强烈变化。尽管在两个溪流中都发现了对叶相关微生物的类似影响，但对暴露的功能反应可能是由于初始微生物群落不同，对干燥胁迫的敏感性不同所致。我们的研究强调了需要了解遭受不同环境干扰的溪流中干旱的影响，因为对暴露的反应似乎取决于环境背景。
