Collaborative Research: LTREB Renewal: Soil Warming and Forest Ecosystem Feedbacks to the Climate System

土壤是陆地生物圈中最大的碳（作为有机物）储存库。如果这些储存的土壤碳通过变暖引起的有机物分解加速转移到大气中，它将导致对全球环境的自我强化（正）反馈。尽管这种土壤反馈具有潜在的重要性，但对影响有机质分解的温度响应的机制还不完全了解。该项目正在量化土壤和生态系统对近三十年土壤变暖的响应，并记录土壤碳对全球环境过程的反馈幅度。广泛培养本科生、研究生和博士后研究人员将是该项目的另一个特点。该研究的数据分析也将被纳入项目负责人教授的课程，并将用于改进陆地生态系统模型预测。该项目正在调查森林生态系统对气候系统反馈的潜在机制，这些反馈是由20多年的原地土壤变暖造成的。具体而言，我们正在量化生物地球化学和微生物对慢性土壤变暖的响应，重点是土壤有机质（SOM）动态。这项研究正在验证一个假设，即长期变暖会导致土壤微生物群落的结构和功能变化周期打断SOM的衰变周期。在哈佛森林长期生态研究（LTER）的三个正在进行的变暖实验中，13,16和28年的土壤温度比环境温度高5摄氏度。总之，这些地点代表了基于单一生态系统类型的共同扰动的动态时间序列。为完成这一长期研究资源项目的十年计划而组织的研究活动围绕四个有针对性的研究问题，这些问题正在通过(1)继续进行核心数据测量来解决；(2)利用原位和实验室条件下的温度操纵，研究土壤呼吸对长期变暖响应的时间非线性模式的潜在机制基础；(3)测量土壤有机质化学和微生物群落动态，以确定长期变暖是否会由于微生物群落结构和/或功能的根本转变而促进和加速顽固性土壤碳的衰变；(4)测量N矿化和地上碳储量，以确定长期变暖是否会继续加速N循环并刺激树木的碳储量；(5)数据整合活动，包括跨站点数据综合和基于微生物特性和生态系统的建模工作。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Soils are the largest repository of carbon (as organic matter) in the terrestrial biosphere. If this stored soil carbon is transferred to the atmosphere by a warming-induced acceleration of organic matter decomposition, it will result in a self-reinforcing (positive) feedback to the global environment. Despite the potential importance of this soil feedback, there is incomplete understanding of the mechanisms that affect the temperature response of organic matter decomposition. This project is quantifying the soil and ecosystem-level responses to nearly three decades of experimental soil warming and documenting the magnitude of soil carbon feedback to global environmental processes. Extensive training of undergraduates, graduate students and postdoctoral researchers will be another feature of this project. Data analysis from the study will also be incorporated into courses taught by the project leaders, and will be used to refine terrestrial ecosystem model projections.This project is investigating the mechanisms underlying feedback from forest ecosystems to the climate system resulting from more than two decades of in situ soil warming. Specifically, we are quantifying the biogeochemical and microbial responses to chronic soil warming, with an emphasis on soil organic matter (SOM) dynamics. This research is testing the hypothesis that long-term warming causes cycles of SOM decay punctuated by periods of structural and functional changes in the soil microbial community. Three ongoing warming experiments at the Harvard Forest Long-term Ecological Research (LTER) site have experienced 5 degrees C above ambient soil temperatures for 13, 16 and 28 years. Together, these sites represent a dynamic time-series based on a common perturbation in a single ecosystem type. Research activities to complete the decadal plan of this LTREB project are organized around four targeted research questions which are being addressed through (1) continuation of core data measurements; (2) temperature manipulations both in situ and under laboratory conditions to examine the underlying mechanistic basis for the observed pattern of temporal non-linearity in the soil respiration response to long-term warming; (3) measurements of SOM chemistry and microbial community dynamics to determine if long-term warming enables and accelerates decay of recalcitrant soil carbon due to a fundamental shift in the structure and/or function of the microbial community; (4) measurements of N mineralization and above-ground carbon storage to determine if long-term warming will continue to accelerate the N cycle and stimulate carbon storage in trees; and (5) data integration activities, including cross-site data syntheses and microbial trait-based and ecosystem modeling efforts.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.