Consequences of seasonal snow cover for carbon cycling of world forests: direct and legacy effects

森林是世界上大部分生物多样性的家园，也为社会带来许多好处，包括提供清洁的空气和水，提供远足等娱乐活动的机会，以及获取木材和药品等宝贵资源。森林还通过空气和树木之间的二氧化碳循环为人类提供了一个鲜为人知的好处。随着人类燃烧化石燃料以获取能源，向空气中排放二氧化碳，大气中的碳含量也在不断积累。空气中额外的二氧化碳改变了自然温室效应，并正在改变全球的温度和天气状况。人类活动增加到空气中的二氧化碳有一部分留在了大气中，而另一部分则被海洋和陆地吸收，尤其是被我们广阔的森林吸收。因此，森林目前对气候变化起到了重要的缓解作用，减缓了气候变化的速度。季节性积雪覆盖的森林覆盖了世界各地的大量土地，将碳储存在树木和土壤中。然而，这些地区正在受到气候条件变化的影响，目前尚不清楚积雪的变化将如何影响森林储存碳的能力。该项目将利用在北半球通量塔研究站点收集的数据，调查积雪对碳循环的独特影响。该项目的成果将促进对雪和树木相互作用的科学理解，并将通过犹他州自然历史博物馆的许多活动与公众分享，让游客参与并提出有关该项目的问题。森林在全球碳循环中发挥着关键作用，与大气交换大量的碳。世界生态系统每年通过呼吸作用向大气释放的二氧化碳比人类通过燃烧化石燃料和土地利用变化释放的二氧化碳多一个数量级。然而，森林通过光合作用吸收的二氧化碳仅比通过呼吸释放的多一点，而且陆地生态系统每年的二氧化碳净吸收率小于人类产生的二氧化碳。这对大气中二氧化碳的增加速度和相关的气候变化提供了重要的缓解效益。然而，森林碳循环存在许多不确定性，阻碍了对未来生态过程的可靠预测。这个项目将为世界范围内积雪覆盖的森林中的碳循环提供机制上的洞察。该项目将调查积雪在森林碳循环中的作用，以揭示反映跨季节生物物理和生物地球化学遗产的直接生物物理和间接控制背后的机制。将使用全球FLUXNET和FLUXNET - canada通量塔网络提供的60多个独特的季节性积雪覆盖森林近600个站点年的碳循环数据。这些站点代表了广泛的气候条件，并将提供关于全球季节性积雪覆盖森林中雪介导的碳循环过程控制的基本信息。这一信息对陆地生物圈模型的发展至关重要，有助于提高我们对季节性积雪生态系统碳通量响应的理解。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。

Forests are host to much of the world's biodiversity, and also provide many benefits to society, including the provisioning of clean air and water, opportunities for recreational activities such as hiking and the acquisition of valuable resources including timber and medicines. Forests also provide a less-appreciated benefit to humans through the cycling of carbon dioxide (CO2) between the air and the trees. As humans add CO2 to the air through the combustion of fossil fuels for energy, the amount of carbon in the atmosphere accumulates. This extra CO2 in the air alters the natural greenhouse effect, and is changing temperature and weather conditions across the planet. Part of the CO2 added to the air by human activities remains in the atmosphere, while some of it is absorbed by the oceans and land, especially by our vast forests. As a result, forests currently provide an important mitigating effect for climate change, slowing the rate of change. Seasonally snow-covered forests cover a large amount of land around the world, storing carbon in both the trees and soils. However, these areas are being modified by changing climate conditions and it is unclear how changes in snowpack will affect the ability of forests to store carbon. This project will investigate the unique influence of the snowpack on carbon cycling by using data collected across the northern hemisphere at research flux tower sites. The results of this project will advance scientific understanding of snow and tree interactions and will also be shared with the public through many activities at the Natural History Museum of Utah, allowing visitors to engage with and ask questions about the project. Forests play a critical role in the global carbon cycle, exchanging large quantities of carbon with the atmosphere. World ecosystems release an order of magnitude more CO2 to the atmosphere via respiration on an annual basis than humans do via combustion of fossil fuels and land use change. However, forests remove just a bit more CO2 via photosynthesis than they release via respiration, and the annual net uptake of CO2 by land ecosystems is smaller than the human CO2 production. This provides an important mitigating benefit to the rate of atmospheric CO2 increase and associated climate change. However, there are many uncertainties about forest carbon cycling that prevent robust forecasts of ecological processes into the future. This project will provide mechanistic insight into carbon cycling in snow-covered forests worldwide. The project will investigate the role of snowpack in forest carbon cycling to uncover the mechanisms behind both direct biophysical and indirect controls that reflect cross-season biophysical and biogeochemical legacies. Nearly 600 site years of carbon cycle data at over 60 unique seasonally snow-covered forests available from the worldwide FLUXNET and Fluxnet-Canada flux tower networks will be used. These sites represent a broad range of climate conditions and will provide fundamental information on the controls of snow-mediated carbon cycle processes across seasonally snow-covered forests globally. This information is crucial for the advancement of terrestrial biosphere models, improving our understanding of carbon flux response in seasonally snow-covered ecosystems.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.