Switching belowground partners: biogeochemical consequences of mycorrhizal type in aspen forests

转换地下伙伴：白杨森林菌根类型的生物地球化学后果

• 批准号: RGPIN-2017-03813
• 负责人: Karst, Justine
• 金额: $ 4.23万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=764525
• 关键词: Switching; belowground; partners; biogeochemical; consequences

Microbes are paramount in the health of humans, their food and the ecosystems with which they interact. Of the microbes that live in soil, fungi are key players in cycling of nutrients and carbon. Fungi decompose organic matter, and through mycorrhizas, a symbiosis between roots and mycorrhizal fungi, they affect the nutrition and growth of plants. The proposed research addresses how soil fungi may mediate changes to soils associated with current range shifts of a widespread tree species. This research is important because it will evaluate how carbon cycling in terrestrial systems is controlled by interactions between trees and fungi, a critical link often overlooked when assessing the impacts of climate change. In western Canada, shifts in forest composition have been predicted and already observed to be intense at the southern limits of boreal forests. Trembling aspen is a widespread tree in this region of range tension, extending north into the boreal forest and south into grasslands. Aspen is also one of the few tree species worldwide that forms symbioses with arbuscular and ectomycorrhizal fungi, the two major groups of mycorrhizas. All mycorrhizal fungi rely on living hosts for carbon, but arbuscular mycorrhizal fungi and ectomycorrhizal fungi differ in their physiology, carbon demands and the extent and types of enzymes excreted into soils. In consequence, the dominance of ectomycorrhizas versus arbuscular mycorrhizas in forests may have pronounced effects on soils. In particular, predicting soil carbon fluxes is imperative as even small changes in fluxes can have substantial impacts on carbon cycling because the soil carbon pool is so large. Little is known on the ecological factors controlling which mycorrhizal type dominates on dually colonized hosts. Over the next five years, my research program will identify causes and consequences of shifts between ectomycorrhizas and arbuscular mycorrhizas in aspen forests occurring in regions of range tension. The anticipated significance of this research is threefold. 1) Historically, these groups of fungi have been studied in isolation. The proposed research considers their interaction as a response to forest dynamics, an innovative perspective ignored to date. 2) Shifts in arbuscular and ectomycorrhizal dominance have been tracked across landscapes, but not within a single, widespread species. Novel approaches described in this proposed research test whether the expression of a changing climate through a single tree species can alter soil fungi to the extent they change nutrient and carbon cycling in soils. 3) The proposed research builds on emerging perspectives on how mycorrhizas mediate carbon fluxes between soils and plants. This perspective is a turning point in recognizing the complex role mycorrhizas play in forests aside from plant nutrition.

微生物在人类健康、食物和与之相互作用的生态系统中至关重要。在生活在土壤中的微生物中，真菌是养分和碳循环的关键参与者。真菌分解有机物质，并通过菌根，根系和菌根真菌之间的共生关系，它们影响植物的营养和生长。拟议的研究解决了土壤真菌如何介导与当前广泛分布的树种的范围变化相关的土壤变化。这项研究很重要，因为它将评估陆地系统中的碳循环如何受到树木和真菌之间相互作用的控制，这是评估气候变化影响时经常被忽视的关键环节。 在加拿大西部，人们预测并观察到北方森林南部界限的森林组成发生了剧烈变化。颤抖的白杨是一种广泛分布的树木在这个地区的范围紧张，延伸到北部的北方森林和南部的草原。白杨也是世界上少数几种与两种主要的菌根丛枝菌和外生菌根真菌形成共生的树种之一。所有的菌根真菌都依赖于活的宿主来获取碳，但丛枝菌根真菌和外生菌根真菌在生理、碳需求以及分泌到土壤中的酶的程度和类型方面有所不同。因此，外生菌根相对于丛枝菌根在森林中的优势可能对土壤产生明显的影响。特别是，预测土壤碳通量是必要的，因为即使是很小的变化通量可以对碳循环产生重大影响，因为土壤碳库是如此之大。很少有人知道的生态因素控制菌根类型占主导地位的双重殖民主机。在接下来的五年里，我的研究计划将确定在范围紧张的地区发生的白杨森林中外生菌根和丛枝菌根之间的转变的原因和后果。这项研究的预期意义有三个方面。1)历史上，这些真菌群一直被孤立地研究。拟议的研究认为，它们之间的相互作用是对森林动态的反应，这是一个迄今为止被忽视的创新观点。2)丛枝菌根和外生菌根优势的变化已经在整个景观中被跟踪，但不是在一个单一的，广泛的物种。在这项拟议的研究中描述的新方法测试了通过单一树种表达气候变化是否可以改变土壤真菌，以改变土壤中的养分和碳循环。3)拟议的研究建立在菌根如何介导土壤和植物之间的碳通量的新兴观点之上。这一观点是认识到除了植物营养之外，菌根在森林中发挥的复杂作用的一个转折点。