LTREB: Following the reorganization and resynchronization of biogeochemical cycles after an unprecedented tundra fire

阿拉斯加林木线以北的北极苔原正在对地球仪上最快的变暖速度做出反应。这些反应包括植物生长增加，底层永久冻土融化，微生物活动增加导致土壤碳流失，以及野火频率和严重程度增加。从历史上看，低温使苔原火灾相对罕见。但预计到2100年，气候变暖将使北极的火灾规模和频率翻一番，从而影响火灾状况。 火灾通过烧毁植被和土壤表层的死亡有机物层，影响冻土带提供的生态系统服务数十年至数百年。当植被在火灾后通过一个被称为演替的过程迅速使景观多样化时，它的组成发生了变化，碳和相关营养物质（如氮和磷）的循环也发生了变化。事实上，火灾带走了植被再生和恢复所需的大部分营养物质，同时，由于绝缘有机层也被移除，土壤温度也随之升高。温暖的土壤可能会增加土壤养分的可用性，并随着时间的推移导致从草地到灌木的转变。但目前还不清楚这些变化是否足以抵消火灾期间最初的碳和营养损失，这是该项目寻求回答的主要问题。除了科学成果，还将制作一个在线纪录片系列，解释气候变化和火灾对北极生态系统的影响。在以前的项目中，专门针对生活在阿拉斯加北坡和印第安纳州的土著和少数民族人口制定的正式推广方案也将得到加强，该项目将制定一个多十年的记录和数学模型，火灾后的碳和养分循环在三个地点沿着最大的北极苔原火灾，从2007年的Anaktuvuk河火灾的干扰严重度梯度。现有的涡度相关系统将用于继续测量2008年开始的碳和能量通量，沿着与土壤室。2011年，在烧伤严重度梯度上进行了定量土壤和生物量收获。火灾后从草地到灌木为主的苔原的轨迹应该会产生积极的气候反馈，并通过减少降雨量产生变暖效应。该项目将用于创建碳、氮和磷通量和储量的多年代记录，以参数化、验证和测试应用于北极苔原生态地球化学的多元素限制（MEL）模型。

The arctic tundra north of the tree line in Alaska is responding to the most rapid rates of warming on the globe. The responses include increased plant growth, thaw of the underlying permafrost, loss of soil carbon through increased microbial activity, and increased frequency and severity of wildfires. Historically, low temperatures have kept tundra fires as relatively infrequent events. But warming is anticipated to impact the fire regime by doubling fire size and frequency in the arctic by the year 2100. Fires impact ecosystem services provided by the tundra for decades to centuries by burning the vegetation and the layer of dead organic matter on top of the soil. As vegetation rapidly recolonizes the landscape after a fire through a process known as succession, its composition changes, as do the cycles of carbon and associated nutrients, like nitrogen and phosphorus. In fact, fires remove a large portion of nutrients needed to fuel the regrowth and recovery of vegetation, while at the same time, increase soil temperatures because the insulating organic layer has also been removed. Warmer soils may increase soil nutrient availability and lead a shift from grasses to shrubs over time. But it is unclear whether these changes are large enough to offset the initial carbon and nutrient losses during the fires, which is the main question this project seeks to answer. Besides the scientific results, an online documentary series will be produced that explains the effects of climate change and fire on arctic ecosystems. Formal outreach programs developed in prior projects that specifically address indigenous and minority populations living on the North Slope in Alaska and in Indiana will also be enhanced.This project will develop a multi-decadal record and mathematical model of post-fire carbon and nutrient cycling across three sites along a disturbance severity gradient within the largest recorded arctic tundra fire, the Anaktuvuk River fire from 2007. An existing eddy covariance system will be used to continue measurements of carbon and energy fluxes begun in 2008, along with soil chambers. A quantitative soil and biomass harvest was conducted in 2011 across a burn severity gradient. Post-fire trajectories from grass to shrub-dominated tundra should create a positive climatic feedback and produce a warming effect through decreased albedo. This project will be used to create a multi-decadal record of carbon, nitrogen and phosphorus fluxes and stocks to parameterize, validate, and test the Multiple Element Limitation (MEL) model as applied to the biogeochemistry of arctic tundra.