Department of Biology and the Ecology Center, Utah State University, Logan, Utah, 84322-5305, USA.
Department of Wildland Resources and the Ecology Center, Utah State University, Logan, Utah, 84322-5230, USA.
Microb Ecol. 2022 Jan;83(1):127-136. doi: 10.1007/s00248-021-01733-8. Epub 2021 Mar 22.
Herbivory can have strong impacts on greenhouse gas fluxes in high-latitude ecosystems. For example, in the Yukon-Kuskokwim (Y-K) Delta in western Alaska, migratory goose grazing affects the magnitude of soil carbon dioxide (CO) and methane (CH) fluxes. However, the underlying drivers of this relationship are unclear, as few studies systematically tease apart the processes by which herbivores influences soil biogeochemistry. To examine these mechanisms in detail, we conducted a laboratory incubation experiment to quantify changes in greenhouse gas fluxes in response to three parameters altered by herbivores in situ: temperature, soil moisture content, and nutrient inputs. These treatments were applied to soils collected in grazing lawns and nearby ungrazed habitat, allowing us to assess how variation in microbial community structure influenced observed responses. We found pronounced differences in both fungal and prokaryotic community composition between grazed and ungrazed areas. In the laboratory incubation experiment, CO and CH fluxes increased with temperature, soil moisture, and goose fecal addition, suggesting that grazing-related changes in the soil abiotic environment may enhance soil C losses. Yet, these abiotic drivers were insufficient to explain variation in fluxes between soils with and without prior grazing. Differences in trace gas fluxes between grazed and ungrazed areas may result both from herbivore-induced shifts in abiotic parameters and grazing-related alterations in microbial community structure. Our findings suggest that relationships among herbivores and soil microbial communities could mediate carbon-climate feedbacks in rapidly changing high-latitude ecosystems.
食草作用对高纬度生态系统的温室气体通量有强烈影响。例如，在阿拉斯加西部的育空-科尤库克三角洲，候鸟放牧会影响土壤二氧化碳（CO）和甲烷（CH）通量的大小。然而，这种关系的潜在驱动因素尚不清楚，因为很少有研究系统地梳理食草动物影响土壤生物地球化学的过程。为了详细研究这些机制，我们进行了一项实验室培养实验，以量化温室气体通量对三种受食草动物原位影响的参数变化的响应：温度、土壤湿度和养分输入。这些处理应用于从放牧草坪和附近未放牧生境采集的土壤中，使我们能够评估微生物群落结构的变化如何影响观察到的响应。我们发现，放牧区和未放牧区的真菌和原核生物群落组成存在明显差异。在实验室培养实验中，CO 和 CH 通量随温度、土壤湿度和鹅粪便添加而增加，这表明与放牧相关的土壤非生物环境变化可能会增强土壤 C 损失。然而，这些非生物驱动因素不足以解释有无先前放牧的土壤之间通量的变化。放牧区和未放牧区之间痕量气体通量的差异可能既来自于食草动物引起的非生物参数变化，也来自于放牧相关的微生物群落结构改变。我们的研究结果表明，食草动物和土壤微生物群落之间的关系可能会调节快速变化的高纬度生态系统中的碳-气候反馈。
