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

土壤是陆地生物圈中碳(作为有机物)的最大储存库。如果这些储存的土壤碳通过变暖导致的有机物分解加速转移到大气中，将导致对全球环境的自我强化(正)反馈。尽管这种土壤反馈的潜在重要性，但对影响有机物分解的温度响应的机制尚不完全了解。该项目正在量化土壤和生态系统层面对近30年来土壤变暖的实验响应，并记录土壤碳对全球环境过程的反馈程度。对本科生、研究生和博士后研究人员的广泛培训将是该项目的另一个特点。这项研究的数据分析还将被纳入项目负责人教授的课程，并将用于完善陆地生态系统模型项目。该项目正在调查20多年来土壤就地变暖导致的森林生态系统对气候系统反馈的潜在机制。具体地说，我们正在量化生物地球化学和微生物对土壤慢性变暖的响应，重点是土壤有机质(SOM)的动态变化。这项研究正在验证一种假设，即长期变暖会导致土壤有机质腐烂的周期，其间伴随着土壤微生物群落结构和功能的变化。哈佛森林长期生态研究(LTER)场地正在进行的三个变暖实验已经经历了13、16和28年来比环境土壤温度高5摄氏度的情况。总而言之，这些地点代表了一个动态的时间序列，基于单一生态系统类型中的共同扰动。完成LTREB项目十年计划的研究活动围绕四个有针对性的研究问题进行，通过(1)持续的核心数据测量；(2)现场和实验室条件下的温度操纵，以检查所观察到的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)土壤有机质化学和微生物群落动力学的测量，以确定长期变暖是否导致和加速了由于微生物群落结构和/或功能的根本性变化而导致的顽固性土壤碳的衰退；(4)N矿化和地上碳储量的测量，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存；以及(5)数据集成活动，包括跨站点数据合成和基于微生物特征的和生态系统建模工作。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.