Collaborative Proposal: MRA: Understanding how local-scale controls on litter decomposition shape emergent macrosystem biogeochemical patterns

合作提案：MRA：了解局部规模的凋落物分解控制如何塑造新兴宏观系统生物地球化学模式

• 批准号: 1926413
• 负责人: William Wieder
• 金额: $ 39.17万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1926413&HistoricalAwards=false
• 关键词: Collaborative; Proposal; MRA; Understanding; how

Decomposition of leaf litter is fundamental to carbon and nutrient cycling in terrestrial ecosystems. Soil animals and microorganisms feed on leaves when they fall to the ground, derive energy and nutrients from consuming the leaves, and then are themselves consumed as part of the food chain. An important result of this process is that nutrients reenter the soil in forms available to plants for new growth. Alternatively, much of the carbon in leaves is released into the atmosphere as carbon dioxide, with a smaller proportion being stored as soil organic carbon, which helps to maintain soil fertility. As such, by mediating leaf degradation, decomposers play a fundamental role in recycling plant nutrients and maintaining soil health. Decades of research on leaf decomposition suggests that the speed at which this process occurs is dependent upon temperature and moisture, as well as the nutritional quality of the leaves. This project will test whether knowledge of these three factors is, in fact, adequate to predict leaf decomposition rates. Recent work suggests that they are not, because soil organisms vary at these scales in their inherent ability to decompose leaf matter. A collaborative team will examine the possibility that the soil animals and microorganisms, themselves, are an additional and important control on decomposition rates. If that is the case, the research will also determine how it changes predictions of nutrient and carbon cycling across the continental US in response to environmental change. The study will examine these questions over regional to continental scales, and thus in the context of plant species variation (which determines leaf nutritional quality), and changes in climate. Accurate predictions of nutrient and carbon cycling are necessary for effective management of ecosystems to provide food, fiber and fuel, as well as to support biodiversity, as the environment changes. Whether differences among belowground heterotrophic communities directly affect macrosystem biogeochemical behavior is unknown. Ecosystem theory and biogeochemical models are based on the assumption that they do not, with different belowground communities then assumed to function similarly under the same environmental conditions. As such, the impact of environmental disturbance on macrosystem biogeochemical patterns should be predictable without understanding site-specific differences in belowground communities. Emerging evidence challenges the validity of this assumption of scale invariance and suggests instead that the activities of decomposer communities are uniquely shaped by regional environment. This project tests these competing hypotheses of scale invariance versus scale dependence for litter decomposition. These competing hypotheses have not been evaluated because the design of previous broad scale decomposition experiments aggregates local-scale responses, creating the possibility of statistical inference fallacies that obscure robust tests of the hypothesis of scale invariance. The project addresses this information gap through field experiments, extensively replicated within 18 National Ecological Observatory Network (NEON) sites arrayed across the eastern United States, which fall within seven ecoclimatic domains. The field research will be combined with controlled laboratory studies to quantify site-specific relationships between temperature, moisture, litter quality and decomposition rates, and to evaluate whether the relationships arise through selection by the domain-level environment for particular microbial functional traits. The mechanistic insights and data generated through this empirical work will inform the structure, and be used to directly estimate the parameters, of a biogeochemical model. The model will be used to forecast the sensitivity of macrosystem behavior to the possibility that it emerges from scale-dependent relationships generated by trade-offs which dictate the activities of belowground communities.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.

凋落叶的分解是陆地生态系统碳和养分循环的基础。土壤动物和微生物在落到地面时以树叶为食，通过消耗树叶获取能量和营养，然后它们本身作为食物链的一部分被消耗。这一过程的一个重要结果是养分以可供植物新生长的形式重新进入土壤。另外，叶子中的大部分碳以二氧化碳的形式释放到大气中，一小部分以土壤有机碳的形式储存，这有助于维持土壤肥力。因此，通过介导叶子降解，分解者在回收植物养分和维持土壤健康方面发挥着重要作用。数十年的叶子分解研究表明，这一过程发生的速度取决于温度和湿度以及叶子的营养质量。该项目将测试这三个因素的知识实际上是否足以预测叶子分解率。最近的研究表明，事实并非如此，因为土壤生物分解叶子物质的固有能力在这些尺度上有所不同。一个合作小组将研究土壤动物和微生物本身对分解率起到额外且重要的控制作用的可能性。如果是这样，该研究还将确定如何改变对美国大陆营养物和碳循环的预测，以应对环境变化。 该研究将在区域到大陆范围内研究这些问题，从而在植物物种变异（决定叶子营养质量）和气候变化的背景下进行研究。随着环境的变化，准确预测养分和碳循环对于有效管理生态系统以提供食物、纤维和燃料以及支持生物多样性是必要的。地下异养群落之间的差异是否直接影响宏观系统的生物地球化学行为尚不清楚。生态系统理论和生物地球化学模型基于这样的假设：不同的地下群落在相同的环境条件下具有相似的功能。因此，在不了解地下群落特定地点差异的情况下，环境扰动对宏观系统生物地球化学模式的影响应该是可以预测的。新出现的证据挑战了这种尺度不变性假设的有效性，并表明分解者群落的活动是由区域环境独特塑造的。该项目测试了垃圾分解的尺度不变性与尺度依赖性的这些相互竞争的假设。这些相互竞争的假设尚未得到评估，因为以前的大规模分解实验的设计聚集了局部尺度的响应，从而产生了统计推断谬误的可能性，从而掩盖了对尺度不变性假设的稳健检验。该项目通过实地实验解决了这一信息差距，并在分布于美国东部的 18 个国家生态观测站网络 (NEON) 站点内进行了广泛复制，这些站点属于七个生态气候领域。现场研究将与受控实验室研究相结合，以量化温度、湿度、凋落物质量和分解率之间的特定地点关系，并评估这些关系是否是通过域级环境对特定微生物功能性状的选择而产生的。通过这项实证工作产生的机制见解和数据将为生物地球化学模型的结构提供信息，并用于直接估计参数。该模型将用于预测宏观系统行为对其从规模依赖关系中出现的可能性的敏感性，这些关系是由决定地下群落活动的权衡产生的。该奖项反映了 NSF 的法定使命，并被认为值得通过以下方式获得支持：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。

项目成果

Soil organic carbon models need independent time-series validation for reliable prediction

土壤有机碳模型需要独立的时间序列验证才能进行可靠的预测

• DOI: 10.1038/s43247-023-00830-5
• 发表时间: 2023
• 期刊: Communications Earth & Environment
• 影响因子: 7.9
• 作者: Le Noë, Julia;Manzoni, Stefano;Abramoff, Rose;Bölscher, Tobias;Bruni, Elisa;Cardinael, Rémi;Ciais, Philippe;Chenu, Claire;Clivot, Hugues;Derrien, Delphine
• 通讯作者: Derrien, Delphine

Patterns and controls of foliar nutrient stoichiometry and flexibility across United States forests

• DOI: 10.1002/ecy.3909
• 发表时间: 2023-01-05
• 期刊: ECOLOGY
• 影响因子: 4.8
• 作者: Dynarski, Katherine A.;Soper, Fiona M.;Cleveland, Cory C.
• 通讯作者: Cleveland, Cory C.