M C Fernandes Vanessa, Rudgers Jennifer A, Collins Scott L, Garcia-Pichel Ferran
Center for Fundamental and Applied Microbiomics, Biodesign Institute, and School of Life Sciences, Arizona State University, Tempe, Arizona, USA.
Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA.
Ecology. 2022 Sep;103(9):e3744. doi: 10.1002/ecy.3744. Epub 2022 Jul 28.
Future climates will alter the frequency and size of rain events in drylands, potentially affecting soil microbes that generate carbon feedbacks to climate, but field tests are rare. Topsoils in drylands are commonly colonized by biological soil crusts (biocrusts), photosynthesis-based communities that provide services ranging from soil fertilization to stabilization against erosion. We quantified responses of biocrust microbial communities to 12 years of altered rainfall regimes, with 60 mm of additional rain per year delivered either as small (5 mm) weekly rains or large (20 mm) monthly rains during the summer monsoon season. Rain addition promoted microbial diversity, suppressed the dominant cyanobacterium, Microcoleus vaginatus, and enhanced nitrogen-fixing taxa, but did not consistently increase microbial biomass. The addition of many small rain events increased microbial biomass, whereas few, large events did not. These results alter the physiological paradigm that biocrusts are most limited by the amount of rainfall and instead predict that regimes enriched in small rain events will boost cyanobacterial biocrusts and enhance their beneficial services to drylands.
未来的气候将改变旱地降雨事件的频率和规模，这可能会影响那些对气候产生碳反馈的土壤微生物，但实地试验却很少见。旱地的表层土壤通常被生物土壤结皮（生物结皮）所覆盖，这是一种基于光合作用的群落，能提供从土壤施肥到防止土壤侵蚀等一系列服务。我们量化了生物结皮微生物群落对12年降雨模式改变的反应，在夏季季风季节，每年额外增加60毫米的降雨量，要么以每周5毫米的小降雨形式，要么以每月20毫米的大降雨形式。增加降雨促进了微生物多样性，抑制了占主导地位的蓝藻——鞘丝藻，并增加了固氮类群，但并没有持续增加微生物生物量。多次小降雨事件的增加会增加微生物生物量，而少量大降雨事件则不会。这些结果改变了生物结皮最受降雨量限制的生理范式，转而预测富含小降雨事件的模式将促进蓝藻生物结皮生长，并增强它们对旱地的有益服务。
