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（有机物）储存库。如果这种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，它将对全球环境产生自我加强的（正）反馈。尽管这种土壤反馈的潜在重要性，有影响有机质分解的温度响应的机制的不完全理解。该项目量化了土壤和生态系统对近三十年实验性土壤变暖的反应，并记录了土壤碳反馈到全球环境过程的程度。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。 该研究的数据分析也将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20多年来原位土壤变暖导致的森林生态系统对气候系统反馈的潜在机制。具体来说，我们正在量化土壤地球化学和微生物对慢性土壤变暖的反应，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衰减周期。三个正在进行的变暖实验在哈佛森林长期生态研究（LTER）网站经历了5摄氏度以上的环境土壤温度为13，16和28年。总之，这些网站代表了一个动态的时间序列的基础上，在一个单一的生态系统类型的共同扰动。为完成LTREB项目的十年期计划，围绕四个有针对性的研究问题组织了研究活动，这些问题正在通过以下方式解决：（1）继续进行核心数据测量;（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的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由于微生物群落的结构和/或功能的根本转变而使柠檬酸盐土壤碳衰减并加速其衰减;（4）测量氮矿化和地上碳储量，以确定长期-长期变暖将继续加速氮循环，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微生物特性-该奖项反映了NSF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.