Collaborative Research: Does tree encroachment with altered hydrology in peatlands accelerate or suppress decomposition?

合作研究：树木侵占会改变泥炭地的水文状况，会加速还是抑制分解？

• 批准号: 2031076
• 负责人: Evan Kane
• 金额: $ 64.73万
• 依托单位: Michigan Technological University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2031076&HistoricalAwards=false
• 关键词: Collaborative; Research; Does; tree; encroachment

Peatlands are important ecosystems in the global carbon (C) cycle owing to their ability to take up and store vast quantities of C under cool and wet conditions. While these conditions have tended to be stable for long periods of time, vast changes are now taking place. Some peatlands have been drained for agriculture or forestry. Others will become warmer and drier in a warming climate. What happens to all the stored C when peatlands are drained or dry up? The answer to this complex question requires understanding the impacts of changes in vegetation, tree growth and peat decomposition below ground through interactions with fungi and other microorganisms. This project will use a large-scale experimental set-up to study the changes that take place underground as peatland soils are drained and trees begin to colonize. Experiments will test how changes in the below ground fungal community accompanying tree roots will impact retention and decomposition of stored C and its potential release into the atmosphere as greenhouse gases like carbon dioxide and methane. Increased retention of peat C would potentially help mitigate global warming while release of greenhouse gases could result in even greater, faster warming. In the course of conducting the research this project will also afford training opportunities for undergraduate and graduate students and outreach to high school teachers and students.Peatlands store about 1/3 of soil C globally in 1/30th of the Earth's land area. Peatland C is vulnerable to oxidation as a result of climate change or water drainage. Peatland C stocks are generally protected under saturated conditions. However many peatlands will become drier in a warming climate. While it is generally assumed that drier conditions will increase decomposition, there are potential feedbacks that lead to major uncertainty in how long-term drying will alter the trajectory of decomposition. For example, drier conditions have been shown to favor the encroachment of woody plant communities in peatlands, which may result in changes in decomposition rates. Changes in the fungal community associated with different plant functional groups (ectomycorrhizal trees, Ericaceae, sedges) are particularly important in mediating changes in decomposition, yet our understanding of how these different fungal groups influence decomposition in situ is rudimentary. The overarching goal of this project is to understand the countervailing effects of woody plant encroachment and long-term drainage on aerobic and anaerobic decomposition in peatlands. Experiments will test two key hypotheses: i) tree encroachment will increase decomposition in drained peatlands as a function of the extracellular enzyme suite of the ectomycorrhizal fungal (EcMF) community; and ii) divergent fungal decomposer pathways and drainage histories will generate peat with differing capacity for donating and accepting electrons under anaerobic conditions. A three-way full factorial experiment will use large, intact peat pedons in a climate controlled mesocosm facility, manipulating peat drainage history, water table position, and tree presence. This will be paralleled by a field experiment in which tree root access will be manipulated over a drainage gradient. The mesocosm approach is the key to this study, so that drainage history and water tables can be manipulated, thus disentangling short- and long-term impacts of changing hydrology. The field experiment will anchor results of the mesocosm manipulations with conditions in the natural environment. Through this and detailed characterization of fungal community functional changes and consequent effects on oxidative enzymes, decomposition, peat chemistry, and "redox pumping" in peat, the project will provide mechanistic insight into the long-term stability of peat in response to altered hydrology. Undergraduate and graduate student training will be integral to the research goals, and the students will help communicate results to high school students and teachers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

泥炭地是全球碳循环中重要的生态系统，因为其在凉爽和潮湿的条件下能够吸收和储存大量的C。虽然这些条件长期以来趋于稳定，但现在正在发生巨大变化。有些泥炭地已排干水用于农业或林业。在气候变暖的情况下，其他地区将变得更加温暖和干燥。当泥炭地被排干或干涸时，所有储存的碳会发生什么变化？这个复杂问题的答案需要了解植被变化的影响，树木生长和泥炭分解地下通过与真菌和其他微生物的相互作用。 该项目将使用一个大规模的实验装置来研究泥炭地土壤被排干和树木开始定植时地下发生的变化。实验将测试伴随树根的地下真菌群落的变化将如何影响储存的C的保留和分解，以及其作为二氧化碳和甲烷等温室气体释放到大气中的可能性。增加泥炭碳的保留可能有助于减缓全球变暖，而温室气体的释放可能导致更大，更快的变暖。在进行研究的过程中，该项目还将为本科生和研究生提供培训机会，并扩大到高中教师和学生。泥炭地在地球陆地面积的1/30中储存了全球约1/3的土壤C。泥炭地C易受气候变化或排水的影响而氧化。泥炭地C种群一般在饱和条件下受到保护。然而，在气候变暖的情况下，许多泥炭地将变得更加干燥。虽然人们通常认为，干燥的条件会增加分解，但有潜在的反馈，导致长期干燥将如何改变分解的轨迹的重大不确定性。例如，干燥的条件已被证明有利于泥炭地木本植物群落的侵入，这可能导致分解率的变化。与不同的植物功能群（外生菌根树，杜鹃花科，莎草）的真菌群落的变化是特别重要的介导的分解变化，但我们的理解这些不同的真菌群体如何影响分解原位是初步的。本项目的首要目标是了解泥炭地木本植物入侵和长期排水对好氧和厌氧分解的抵消作用。实验将测试两个关键的假设：i）树木侵占将增加分解排水泥炭地作为功能的胞外酶套件的外生菌根真菌（EcMF）社区;和ii）不同的真菌分解途径和排水历史将产生泥炭与不同的能力，在厌氧条件下捐赠和接受电子。一个三向全因子实验将使用大，完整的泥炭pedons在气候控制的围隔设施，操纵泥炭排水的历史，地下水位的位置，和树木的存在。这将通过一个实地实验来验证，在这个实验中，树根的进入将被操纵在排水梯度上。中尺度生态系统方法是这项研究的关键，因此可以操纵排水历史和地下水位，从而解开水文变化的短期和长期影响。野外实验将使围隔生态系统操作的结果与自然环境条件锚在一起。通过这个和详细的表征真菌群落功能的变化和随之而来的影响氧化酶，分解，泥炭化学，和“氧化还原泵”在泥炭，该项目将提供机制洞察泥炭的长期稳定性，以应对水文变化。本科生和研究生的培训将是研究目标不可或缺的一部分，学生将帮助交流结果给高中学生和教师。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。