Collaborative Research LTREB: Soil warming and forest ecosystem feedbacks to the climate system

合作研究LTREB：土壤变暖和森林生态系统对气候系统的反馈

• 批准号: 1456610
• 负责人: Serita Frey
• 金额: $ 10.45万
• 依托单位: University of New Hampshire
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1456610&HistoricalAwards=false
• 关键词: Collaborative; Research; LTREB; Soil; warming

Soils store at least three times more carbon in soil organic matter (SOM) than either the atmosphere or vegetation. The response of SOM to increasing temperature is an important aspect of the interactions between ecosystems and climate. If increasing temperatures cause soil carbon to be transferred to the atmosphere, the result would be a self-reinforcing (positive) feedback to the climate system, with warming leading to more warming. Despite the potential importance of this feedback, there is currently an incomplete understanding of the mechanisms that affect the temperature sensitivity of SOM. This project will continue a long running soil warming experiment at Harvard Forest which is currently in its third decade. The experiments use heated cables to warm the soil in a mature eastern forest. To date, the results of this experiment have shown dynamic responses of SOM to temperature over time. This project will continue to study and monitor long-term soil responses to warming to advance the scientific understanding of how temperature controls decomposition of SOM on a decadal time scale. The results will improve the representation of soil processes in the Earth system models that are used to project future climate.Ongoing field warming experiments in the deciduous forest stands at Harvard Forest have imposed 5oC above ambient soil temperatures at three replicated sites for 8, 11 and 23 years, which now correspond to three distinct phases of CO2 emissions in the longest running experiment. There was an initial increase in soil respiration in response to warming in the first decade, followed by no response, and finally another period of higher soil respiration in the heated plots in the last 8 years. The chronosequence of the three warming experiments offers a unique opportunity to understand how increasing soil temperatures affect soil biogeochemistry, plant-soil interactions, and microbial community composition over time. The research has three major components: 1) continuation of core measurements of carbon and nitrogen stocks and fluxes; 2) short-term temperature manipulations combined with measurements of key indicators of biogeochemical and microbial community changes; and 3) targeted process-level measurements that enhance a mechanistic understanding of soil responses to long-term warming. The project will measure the isotopic composition of carbon and nitrogen, the chemical composition of SOM, and microbial community composition along the chronosequence. The soil warming experiments will continue to operate as an open facility for students and researchers nationwide to study the long-term effects of warming on ecosystem processes.

土壤有机质 (SOM) 中储存的碳至少是大气或植被中碳的三倍。 SOM 对温度升高的响应是生态系统与气候相互作用的一个重要方面。如果气温升高导致土壤碳转移到大气中，结果将是对气候系统的自我强化（正）反馈，变暖导致进一步变暖。 尽管这种反馈具有潜在的重要性，但目前对影响 SOM 温度敏感性的机制尚不完全了解。该项目将继续在哈佛森林进行长期土壤变暖实验，该实验目前已进入第三个十年。 实验使用加热电缆来加热东部成熟森林中的土壤。 迄今为止，该实验的结果显示了 SOM 对温度随时间的动态响应。 该项目将继续研究和监测土壤对变暖的长期反应，以促进对温度如何在十年时间尺度上控制 SOM 分解的科学理解。研究结果将改善用于预测未来气候的地球系统模型中土壤过程的表征。哈佛森林落叶林中正在进行的野外增温实验已在 8、11 和 8 年的时间里在三个重复地点使土壤温度比环境温度高出 5 摄氏度。 23 年，现在相当于运行时间最长的实验中二氧化碳排放的三个不同阶段。 在最初的十年里，土壤呼吸最初因气候变暖而增加，随后没有任何反应，最后在过去的八年里，炎热地区的土壤呼吸又出现了一个较高的时期。这三个变暖实验的时间顺序提供了一个独特的机会，可以了解随着时间的推移，土壤温度升高如何影响土壤生物地球化学、植物-土壤相互作用和微生物群落组成。该研究由三个主要部分组成：1）继续进行碳和氮储量及通量的核心测量； 2）短期温度操纵结合生物地球化学和微生物群落变化关键指标的测量； 3）有针对性的过程水平测量，增强对土壤对长期变暖反应的机械理解。该项目将测量碳和氮的同位素组成、SOM 的化学组成以及沿时间顺序的微生物群落组成。 土壤变暖实验将继续作为一个开放设施，供全国学生和研究人员研究变暖对生态系统过程的长期影响。