Turbo-charging the mycorrhizosphere - Could more productive ecosystems threaten soil carbon stocks in boreal and sub-arctic zones of transition?

菌根圈的涡轮增压——生产力更高的生态系统是否会威胁到北方和亚北极过渡区的土壤碳储量？

• 批准号: NE/X015076/1
• 负责人: Philip Wookey
• 金额: $ 85.04万
• 依托单位: University of Stirling
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX015076%2F1
• 关键词: Turbo; charging; mycorrhizosphere; Could; more

The Context of the Research - Many high-profile research papers and syntheses have equated increased vegetation productivity and shifting vegetation types in northern high latitudes with increased net carbon (C) sequestration from the atmosphere. Although logical and intuitive, this largely overlooks the potential fate of pre-existing soil organic carbon (SOC) in these regions. This is a problem because soils at high latitudes are notably C-rich (containing ~570 Pg C in boreal/taiga forest and tundra soils alone; note, 1 Pg (Peta-gram) = 1,000,000,000 tonnes) and this pool is dynamic, intrinsically interacting both with vegetation cover and with climate.Although challenging to investigate, we cannot overlook below-ground processes if we are to understand net C budgets on timescales relevant to the Climate Emergency. Understanding the fundamental mechanisms controlling the accumulation, stability, and loss of soil organic matter (SOM) is as essential for predicting the Earth's future climate as understanding photosynthesis and plant productivity. However, our understanding of, and ability to model, SOM dynamics lags far behind that of primary productivity. Furthermore, rapid warming at high northern latitudes adds urgency to understanding controls on whole-ecosystem C cycling, net fluxes of CO2 between ecosystems and the atmosphere, and the vulnerability of SOM to changes in both climate and management (for example, tree planting for C-sequestration).Aims and Objectives - In MYCONET we focus on the 'mycorrhizosphere' (the soil and organisms directly influenced by roots and their mycorrhizal fungi) of C-rich soils of northern high latitudes and its potential response both to increasing plant productivity and to shifts to woodier shrub and tree communities. We hypothesise that associated changes in the mycorrhizosphere could, paradoxically, result in net losses, rather than gains, of soil C over timescales (i.e. several decades) of relevance to the Climate Emergency. This would represent a 'positive feedback' on climate change (i.e. when the rates of CO2 emission to the atmosphere, due to SOM decomposition, exceed net rates of CO2 uptake via photosynthesis).We will push the frontiers by applying ground-breaking techniques in the use - and innovative experimental deployment - of natural abundance (and depleted) radiocarbon (14C), together with metagenomics, soil and root-tip enzyme assays and SOM chemistry, to quantify and understand the processes and dynamics of the mycorrhizosphere and how these affect SOC stocks. We focus, in detail, on the process of 'priming' (which occurs when material added to soil affects the rate of decomposition of SOM, either positively or negatively), and the specific role of mycorrhizal fungi in this, and related, processes. We will measure these processes both in situ (in the Arctic and the UK uplands) and in controlled experiments (using specific combinations of tree, shrub and mycorrhizal symbionts), as part of an integrated package of mechanistic studies, soil profile analysis and dynamic SOM modelling, to quantify and understand how priming works, and the implications for SOM dynamics, ecosystem C fluxes, and nutrient cycling. Potential applications and benefits - By applying ground-breaking techniques MYCONET will transform our understanding of plant-soil interactions and the role of mycorrhizal fungi in SOM dynamics. The fundamental new knowledge gained will significantly improve regional and global modelling of climate-biogeochemical interactions, with a particular focus on the indirect effects of shifting plant communities. The project has relevance for the pan-Arctic 'shrubification', as well as for ecosystems being managed for C-sequestration or 're-wilding'. This project is especially timely, given the major policy emphasis and public interest in tree planting for C sequestration.

研究背景-许多引人注目的研究论文和综合报告将北方高纬度地区植被生产力的提高和植被类型的变化与大气中碳（C）净固存量的增加等同起来。虽然逻辑和直观，这在很大程度上忽略了这些地区预先存在的土壤有机碳（SOC）的潜在命运。这是一个问题，因为高纬度地区的土壤明显富含碳（仅在北方针叶林和冻原土壤中含~570 PgC;注：1 Pg（Peta-gram）= 1，000，000，000吨），这一储量是动态的，与植被和气候有着内在的相互作用。尽管调查具有挑战性，如果我们要理解与气候紧急情况相关的时间尺度上的净碳预算，我们就不能忽视地下过程。了解控制土壤有机质（SOM）积累、稳定和流失的基本机制，对于预测地球未来气候和了解光合作用和植物生产力一样重要。然而，我们的理解和建模能力，SOM动态远远落后于初级生产力。此外，北方高纬度地区的快速变暖增加了了解整个生态系统C循环控制、生态系统和大气之间的CO2净通量以及SOM对气候和管理变化的脆弱性的紧迫性（例如，目的和目标-在MYCONET中，我们专注于“菌根圈”（直接受根系及其菌根真菌影响的土壤和生物体）及其对提高植物生产力和向木本灌木和乔木群落转移的潜在反应。我们假设，相关的变化在菌根可能，矛盾的是，导致净损失，而不是收益，土壤碳在时间尺度（即几十年）的相关性的气候紧急情况。这将是对气候变化的“积极反馈”（即当由于SOM分解而导致的CO2排放到大气中的速率超过通过光合作用吸收CO2的净速率时）。我们将通过在自然丰度的使用和创新实验部署中应用突破性技术来推动前沿（和耗尽）放射性碳（14 C），连同宏基因组学，土壤和根尖酶测定和SOM化学，以量化和了解的过程和动态的菌根以及这些如何影响SOC股票。我们专注于，在详细的过程中，“启动”（发生时，添加到土壤中的材料会影响SOM的分解率，无论是积极的还是消极的），以及菌根真菌在这个过程中的具体作用，相关的，过程。我们将测量这些过程都在原位（在北极和英国高地），并在控制实验（使用特定组合的树，灌木和菌根共生体），作为一个综合的一揽子机制研究，土壤剖面分析和动态SOM建模的一部分，量化和了解如何启动工程，以及SOM动态，生态系统碳通量和养分循环的影响。潜在的应用和好处-通过应用突破性的技术，MYCONET将改变我们对植物-土壤相互作用和菌根真菌在SOM动态中的作用的理解。获得的基本新知识将大大改善气候-地球化学相互作用的区域和全球建模，特别关注植物群落迁移的间接影响。该项目与泛北极“灌木化”以及为碳固存或“再野生化”而管理的生态系统有关。考虑到植树固碳的主要政策重点和公众利益，该项目特别及时。