Decomposition of ectomycorrhizal fine roots

外生菌根细根的分解

• 批准号: RGPIN-2015-04323
• 负责人: Kernaghan, Gavin
• 金额: $ 1.75万
• 依托单位: Mount Saint Vincent University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=679622
• 关键词: Decomposition; ectomycorrhizal; fine; roots

Trees allocate a large portion of their productivity to their fine feeder roots. In northern forests, the majority of these roots are colonized by ectomycorrhizal fungi - fungal symbionts that aid in nutrient and water uptake in exchange for plant sugars. Although the turnover of ectomycorrhizal fine roots represents an enormous input of carbon and nitrogen into the soil ecosystem, we have very little information regarding the decomposers involved, and therefore the fate of the resources liberated. Ectomycorrhizal fine roots are approximately 40% fungal tissue, which contains chitin and therefore significantly more nitrogen than plant tissue. However, it is not clear which organisms dominate the breakdown of fungi in forest soils. Bacterial vs fungal decomposition impacts both soil nutrient availability and carbon sequestration, as resources move more quickly through bacterial communities than through fungal communities. Bacteria are thought to be the dominant decomposers of chitin in alkaline soils, and soil fungi are considered to be more important under acidic conditions. However, bacterial decomposition of fungi may increase with higher temperatures, such that a larger proportion of fungal carbon and nitrogen may move through the more labile bacterial community in a warmer climate. Fine roots are also colonized internally by fungal endophytes. Although the ecological roles of these fungi are poorly understood, they may be involved in the decomposition of the plant component of ectomycorrhizae, and are well positioned within the root tissue. The symbiotic fungus forming a given ectomycorrhiza may also influence its decomposition rate, as some species produce antimicrobial compounds. ***The objectives of the proposed research are to: 1) determine which decomposers utilize the fungal component of ectomycorrhizae under different environmental conditions using DNA based techniques, 2) track microbial activity during the decomposition of whole ectomycorrhizae using RNA techniques (gene expression) and 3) determine the decomposition rates of ectomycorrhizae formed by different fungal species, characterizing the antimicrobial compounds produced by recalcitrant species. ***A prominent feature of the Canadian landscape is the boreal forest, an ecosystem in which all dominant tree species form ectomycorrhizae. Knowing the relative importance of bacteria, soil fungi, root endophytes and ectomycorrhizal fungi in the process of fine root decomposition is key to resolving the pathways though which the resulting fluxes of resources move through our northern forests. Information on the dynamic roles of soil microbes under varying environmental conditions, including those expected under climate change, is also critical to understanding present and future boreal forest ecosystem function. ********

树木将其生产力的很大一部分分配给其优良的饲养根。在北方的森林中，这些根中的大多数被外生菌根真菌--真菌共生体--定殖，这些真菌共生体帮助养分和水分的吸收，以交换植物糖。虽然外生菌根细根的周转代表了土壤生态系统中碳和氮的巨大输入，但我们对所涉及的分解者以及所释放的资源的命运知之甚少。外生菌根细根约40%是真菌组织，其中含有几丁质，因此比植物组织显着更多的氮。然而，目前还不清楚哪些生物主导森林土壤中真菌的分解。细菌与真菌的分解影响土壤养分的有效性和碳固存，因为资源通过细菌群落比通过真菌群落移动得更快。细菌被认为是碱性土壤中几丁质的主要分解者，而土壤真菌被认为在酸性条件下更重要。然而，真菌的细菌分解可能会随着温度的升高而增加，使得更大比例的真菌碳和氮可能会在更温暖的气候中通过更不稳定的细菌群落移动。细根也被真菌内生菌在内部定殖。虽然这些真菌的生态作用知之甚少，它们可能参与外生菌根的植物成分的分解，并很好地定位在根组织内。形成给定外生菌根的共生真菌也可能影响其分解速率，因为某些物种产生抗菌化合物。* 拟议研究的目标是：1）使用基于DNA的技术确定哪些分解者在不同环境条件下利用外生真菌的真菌组分，2）使用RNA技术跟踪整个外生真菌分解期间的微生物活性（基因表达）和3）确定由不同真菌物种形成的外生真菌的分解速率，表征由柠檬酸盐物种产生的抗微生物化合物。* 加拿大地貌的一个突出特点是北方森林，在这个生态系统中，所有主要树种都形成外生菌根。了解细菌、土壤真菌、根内生菌和外生菌根真菌在细根分解过程中的相对重要性，是解决由此产生的资源通量通过我们北方森林移动的途径的关键。关于土壤微生物在不同环境条件下的动态作用的信息，包括在气候变化下预期的信息，对于了解目前和未来的北方森林生态系统功能也至关重要。 ********