Collaborative Research: RAPID: Mechanisms and fate of fire-induced carbonate formation in a cold desert ecosystem

旱地一直与野火联系在一起，但气候变化和植被的变化改变了这些敏感生态系统的火灾制度和碳平衡。野火吞噬植被，释放储存的有机碳，形成二氧化碳(CO2)，这是一种温室气体。然而，最近观察到旱地野火后以土壤碳酸盐(即无机碳)形式积累的盐分。火诱导碳酸盐积累(FICA)的机制及其对长期碳储存的重要性仍不清楚。这项研究开始解决我们对火灾引起的土壤碳酸盐的起源、命运和影响的认识空白，因为野火活动在旱地处于历史最高水平。在这里，研究人员使用预定于2023年9月在美国农业部西北流域研究中心(NWRC)和临界区天文台(CZO)已经密集测量的集水区使用规定的牧场火灾来表征火灾引起的碳酸盐积累的环境控制。这项研究是一个由研究人员和土地管理人员组成的跨学科小组的一部分，他们合作加强对野地火灾的了解，以产生更大的区域影响。这项研究将利用2023年9月的一场实验火灾来表征导致火灾诱导碳酸盐积累(FICA)的非生物因素，该火灾位于爱达荷州南部及其周边地区寒冷的沙漠、山艾树草原生态系统内。土壤pH、钙有效性、土壤二氧化碳(CO2)浓度和胞外酶活性等一系列因素似乎导致了FICA，但涉及的确切机制以及这种碳的来源和去向仍未解决。在牧场野火研究中不同寻常的是，该项目将1)在火灾前收集土壤样本，并将这些样本与火灾后的条件进行对比，以便于未来对FICA的控制进行调查；2)测量火灾前、火灾期间和火灾后9个月的土壤二氧化碳、水分和温度条件-这是一个独特且易腐烂的数据集，而且从未被用来研究火灾导致碳酸盐形成的机制。样本收集和传感器测量将分南北两个方面进行，并对烧伤严重程度处理(即植被类型)进行分层，以了解FICA上的景观控制。土壤样本也被认为是易腐烂的，将被存档以供在初始pH、EC和碳酸盐测定之后的未来调查。这一裁决反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Drylands have always been linked with wildfires, but climate change and shifts in vegetation have altered the fire regime and carbon balance of these sensitive ecosystems. Wildfires consume vegetation, releasing stored organic carbon as carbon dioxide (CO2), a greenhouse gas. Recently, however, the accumulation of salts in the form of soil carbonates (i.e., inorganic carbon) have been observed after dryland wildfires. The mechanisms of fire-induced carbonate accumulation (FICA) and its importance to long-term carbon storage remain unknown. This research begins to address a gap in our knowledge about the origin, fate, and impact of fire-induced soil carbonates as wildfire activity is at its historic highest levels in drylands. Here, researchers characterize the environmental controls on fire-induced carbonate accumulation using a prescribed rangeland fire slated for September 2023 in an already intensively instrumented catchment of the US Department of Agriculture’s Northwest Watershed Research Center (NWRC) and Critical Zone Observatory (CZO). The research is part of an interdisciplinary group of researchers and land managers collaborating to enhance understanding of wildland fires to create greater regional impact. This research will characterize the abiotic factors contributing to fire-induced carbonate accumulation (FICA) using an experimental fire in September 2023, located within the cold desert, sagebrush steppe ecosystem characteristic of southern Idaho and the surrounding region. A combination of factors including soil pH, calcium availability, soil carbon dioxide (CO2) concentration, and extracellular enzymatic activity appear to lead to FICA, but the exact mechanisms involved, and the source and fate of this carbon remain unresolved. Uncommon in rangeland wildfire studies, the project will 1) collect soil samples just before the fire, and contrast these with post-fire conditions to facilitate future investigation of controls on FICA, and 2) measure soil CO2, moisture, and temperature conditions before, during, and for 9 months after the fire – a unique and perishable dataset, and something that has never been done to study the mechanisms driving carbonate formation caused by fires. Sample collection and sensor measurements will be stratified across north- and south-facing aspects, and burn severity treatments (i.e., vegetation types) to understand landscape controls on FICA. Soil samples are also considered perishable and will be archived for future investigation beyond initial pH, EC, and carbonate determination.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.