Hawkesbury Institute of Environment, Western Sydney University, Penrith, NSW, Australia.
School of Science, Western Sydney University, Penrith, NSW, Australia.
Microb Ecol. 2023 Nov;86(4):3097-3110. doi: 10.1007/s00248-023-02303-w. Epub 2023 Oct 25.
Drylands comprise one-third of Earth's terrestrial surface area and support over two billion people. Most drylands are projected to experience altered rainfall regimes, including changes in total amounts and fewer but larger rainfall events interspersed by longer periods without rain. This transition will have ecosystem-wide impacts but the long-term effects on microbial communities remain poorly quantified. We assessed belowground effects of altered rainfall regimes (+ 65% and -65% relative to ambient) at six sites in arid and semi-arid Australia over a period of three years (2016-2019) coinciding with a significant natural drought event (2017-2019). Microbial communities differed significantly among semi-arid and arid sites and across years associated with variation in abiotic factors, such as pH and carbon content, along with rainfall. Rainfall treatments induced shifts in microbial community composition only at a subset of the sites (Milparinka and Quilpie). However, differential abundance analyses revealed that several taxa, including Acidobacteria, TM7, Gemmatimonadates and Chytridiomycota, were more abundant in the wettest year (2016) and that their relative abundance decreased in drier years. By contrast, the relative abundance of oligotrophic taxa such as Actinobacteria, Alpha-proteobacteria, Planctomycetes, and Ascomycota and Basidiomycota, increased during the prolonged drought. Interestingly, fungi were shown to be more sensitive to the prolonged drought and to rainfall treatment than bacteria with Basidiomycota mostly dominant in the reduced rainfall treatment. Moreover, correlation network analyses showed more positive associations among stress-tolerant dominant taxa following the drought (i.e., 2019 compared with 2016). Our result indicates that such stress-tolerant taxa play an important role in how whole communities respond to changes in aridity. Such knowledge provides a better understanding of microbial responses to predicted increases in rainfall variability and the impact on the functioning of semi-arid and arid ecosystems.
干旱地区占地球陆地表面的三分之一，为超过 20 亿人提供支持。预计大多数干旱地区的降雨模式将发生变化，包括总降雨量的变化和较少但更大的降雨事件，其间会有更长时间没有降雨。这种转变将对生态系统产生广泛影响，但微生物群落的长期影响仍未得到充分量化。我们在 2016 年至 2019 年期间，在澳大利亚干旱和半干旱地区的六个地点评估了改变的降雨模式（相对于环境增加 65%和减少 65%）的地下效应，这与一次重大的自然干旱事件（2017-2019 年）同时发生。微生物群落在半干旱和干旱地区之间以及在不同年份之间存在显著差异，这与 pH 值和碳含量等非生物因素的变化以及降雨有关。降雨处理仅在一部分地点（米尔帕林卡和奎尔皮）引起了微生物群落组成的变化。然而，差异丰度分析显示，一些类群，包括 Acidobacteria、TM7、Gemmatimonadates 和 Chytridiomycota，在最湿润的年份（2016 年）更为丰富，而在较干燥的年份其相对丰度下降。相比之下，贫营养类群如 Actinobacteria、Alpha-proteobacteria、Planctomycetes 和 Ascomycota 和 Basidiomycota 的相对丰度在长时间干旱期间增加。有趣的是，真菌比细菌对长时间干旱和降雨处理更为敏感，在减少降雨处理中 Basidiomycota 占主导地位。此外，相关网络分析显示，干旱后（即 2019 年与 2016 年相比），耐应激优势类群之间的正相关性更高。我们的结果表明，这种耐应激类群在整个群落对干旱变化的反应中起着重要作用。这种知识提供了对微生物对预测增加的降雨变异性的反应以及对半干旱和干旱生态系统功能的影响的更好理解。
