Collaborative Research: Investigating the soil-earthworm-litter system controls on the stabilization of soil organic matter in Eastern deciduous forests

合作研究：调查土壤-蚯蚓-凋落物系统对东部落叶林土壤有机质稳定的控制作用

• 批准号: 0748574
• 负责人: Katalin Szlavecz
• 金额: $ 15.1万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0748574&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; soil; earthworm

ABSTRACTSoil organic matter (SOM) and associated litter represents the largest actively cycling pool of organic carbon (OC) and nitrogen (ON). Because soil acts as both a sink and a source for carbon, a detailed, mechanistic understanding of the controls on the conversion of litter OM to SOM, and its stability in soil is critical to accurately account for the changing balance between the atmospheric, terrestrial plant, and soil carbon reservoirs. In mid continent and northern North American forests there is an increasing awareness of the effect that detritivore macroinvertebrates, specifically earthworms (EW), have on litter decay dynamics and the associated nature of stabilized SOM. Well-documented effects of earthworm introduction into forests with few or no native EW include the depletion of organic horizons, forest floor litter, loss of soluble nutrients, and mixing of mineral and organic horizons. Surprisingly, however, earthworm activity, with its feedbacks to enzymatic activity, microbial community structure, and plant biopolymer alteration, is generally not one of the considerations applied to influences on SOM stabilization. This proposal seeks to document and quantify how these protective mechanisms interact in natural and experimental systems impacted by different degrees of EW activity. Our focus is primarily on identifying how differences in invasive EW activity and feeding habit interact with differences in litter chemical composition, mineralogy, and microbial enzyme activity among locations in the same temperate forest to alter the relative importance of physical, chemical, and biochemical protection mechanisms controlling SOM stabilization. This interdisciplinary, collaborative proposal presents a series of hypotheses and experiments to test fundamental components of the EW-Litter-SOM dynamics as summarized in the following four questions: 1). Do EW promote a different decay path for litter, reflected in its biopolymer, elemental, and isotopic composition, that might impact its biochemical recalcitrance and thus SOM stabilization? 2). How will the degree of stabilization and the biopolymer character of plant/microbial OM incorporated in EW casts be influenced by EW feeding habit, initial litter chemistry, and the microbial and mineral composition of soil? 3) Given that earthworms are known to impact soil structure and carbon allocation (i.e. litter translocation and incorporation of their casts with associated stable microstructures into soil) how will the known gradient in earthworm activity and litter chemistry across our field sites impact the specific source, chemistry, and amount of SOM that is biochemically protected (i.e. refractory biopolymers) and/or physically and chemically protected (i.e. aggregated and mineral associated)? 4) How will forest ecosystems at different levels of earthworm activity differ in the rate at which its soil organic carbon (SOC) moves through the terrestrial soil carbon reservoir? This work will employ detailed molecular, isotopic, mineralogical, ecological and microbiological methods to develop a mechanistic understanding of the processes that control soil organic matter storage in a system with a intense gradient in EW activity. To accomplish these tasks we have assembled an interdisciplinary team that includes a molecular and stable isotope biogeochemist, a soil molecular ecologist, a soil mineral-chemist, and an earthworm ecologist whose combined expertise is well suited to investigate the impacts of this ecological change on the stability of SOM. The intellectual merit of this proposal rests on the importance of these factors for soil carbon cycling, the lack of existing knowledge about these questions, the multidisciplinary perspective we apply, and the qualifications of the PIs. Additionally, this work has significant potential to benefit the SOM modeling community, which struggles for physically meaningful analyses that permit modeling of SOM dynamics. The EW-litter-soil system is particularly relevant today as most identified EW species in this region?s forests are non-native, and it is anticipated that over the next few decades they will expand farther into northern forests driven by rising surface temperatures, and local factors, e.g. soil transport, discarded fishing bait, and land use change. Knowledge gained from this study will contribute to the general understanding of major drivers in carbon cycling in Eastern deciduous forests of North America. The broader impacts of this work include the enhanced understanding of the role earthworms in driving change in north American forest soil processes and biogeochemical cycles that will be of great significance to both scientists and policy-makers. Additionally, the project will educate two Ph.D. students and numerous undergraduates, with great potential to attract underrepresented students through Purdue?s NSF-Funded AGEP and Native American programs, SERC?s REU program, and Johns Hopkins? Provost Undergraduate Research Award and will provide information for a high school teaching module.

摘要：土壤有机质 (SOM) 和相关凋落物代表了最大的有机碳 (OC) 和氮 (ON) 活跃循环池。由于土壤既是碳汇又是碳源，因此详细、机械地了解凋落物 OM 转化为 SOM 的控制及其在土壤中的稳定性对于准确解释大气和陆地植物之间不断变化的平衡至关重要和土壤碳库。在中部大陆和北美北部森林中，人们越来越认识到食碎屑大型无脊椎动物，特别是蚯蚓 (EW) 对凋落物腐烂动态和稳定 SOM 的相关性质的影响。有据可查的是，蚯蚓引入很少或根本没有天然电子水的森林会产生影响，包括有机地层的消耗、森林地表垃圾、可溶性营养物质的损失以及矿物质和有机地层的混合。然而，令人惊讶的是，蚯蚓活性及其对酶活性、微生物群落结构和植物生物聚合物改变的反馈，通常不是影响 SOM 稳定性的考虑因素之一。该提案旨在记录和量化这些保护机制如何在受不同程度电子战活动影响的自然和实验系统中相互作用。我们的重点主要是确定同一温带森林中不同地点的入侵电子战活动和摄食习惯的差异如何与凋落物化学成分、矿物学和微生物酶活性的差异相互作用，从而改变物理、化学和生化保护机制的相对重要性控制 SOM 稳定性。这个跨学科的协作提案提出了一系列假设和实验来测试 EW-Litter-SOM 动力学的基本组成部分，总结为以下四个问题：1)。 EW 是否会促进垃圾的不同腐烂路径（反映在其生物聚合物、元素和同位素组成中），这可能会影响其生化顽抗性，从而影响 SOM 的稳定性？ 2）。 EW 铸件中加入的植物/微生物 OM 的稳定程度和生物聚合物特性将如何受到 EW 摄食习惯、初始垫料化学以及土壤微生物和矿物质组成的影响？ 3) 鉴于已知蚯蚓会影响土壤结构和碳分配（即凋落物易位以及将其铸件与相关的稳定微观结构结合到土壤中），已知的蚯蚓活动梯度和整个田间的凋落物化学将如何影响特定来源，化学性质，以及受生化保护（即难熔生物聚合物）和/或物理和化学保护（即聚集和矿物相关）的 SOM 量？ 4）不同蚯蚓活动水平的森林生态系统其土壤有机碳（SOC）穿过陆地土壤碳库的速率有何不同？这项工作将采用详细的分子、同位素、矿物学、生态和微生物学方法，从机械角度理解控制土壤有机质储存的过程，该系统具有强烈的电子波活动梯度。为了完成这些任务，我们组建了一个跨学科团队，其中包括一名分子和稳定同位素生物地球化学家、一名土壤分子生态学家、一名土壤矿物化学家和一名蚯蚓生态学家，他们的综合专业知识非常适合研究这种生态变化对地球的影响。 SOM 的稳定性。该提案的学术价值在于这些因素对土壤碳循环的重要性、对这些问题现有知识的缺乏、我们采用的多学科视角以及 PI 的资格。此外，这项工作具有使 SOM 建模社区受益的巨大潜力，该社区正在努力进行具有物理意义的分析，以允许对 SOM 动态进行建模。 EW-凋落物-土壤系统在今天尤其重要，因为该地区森林中大多数已识别的EW物种都是非本地物种，预计在未来几十年内，由于地表温度上升，它们将进一步扩展到北部森林，以及当地因素，例如土壤迁移、废弃鱼饵和土地利用变化。从这项研究中获得的知识将有助于全面了解北美东部落叶林碳循环的主要驱动因素。这项工作的更广泛影响包括加深对蚯蚓在驱动北美森林土壤过程和生物地球化学循环变化中的作用的了解，这对科学家和政策制定者都具有重要意义。此外，该项目还将培养两名博士生。学生和众多本科生，通过普渡大学 NSF 资助的 AGEP 和美洲原住民项目、SERC 的 REU 项目和约翰·霍普金斯大学，有巨大的潜力吸引代表性不足的学生？教务长本科生研究奖将为高中教学模块提供信息。