RAPID: Responses of Soil Organic Carbon Chemistry to Wildfires across a Rainfall Gradient

土壤有机碳（SOC）在很大程度上决定了土壤的健康、功能和生产力。因此，有机碳的积累可以促进气候变化，并受到野火的影响，野火在美国和世界各地发生的频率和强度都在增加。野火通过影响有机碳储存、土壤侵蚀和养分循环的方式改变有机碳的化学成分和含量。虽然野火发生在广泛的气候条件下，但了解野火对有机碳化学的影响非常重要。这个RAPID项目的目标是研究气候如何影响森林有机碳的化学成分。土壤样本将在2023年8月发生野火的夏威夷毛伊岛的降雨梯度上收集。该项目将对夏威夷及其他地区的牧场和森林管理产生重要影响。在野火发生后，需要立即收集土壤，以了解野火如何影响有机碳化学和土壤性质。野火后土壤有机碳的初始化学性质控制着土壤的疏水性，疏水性直接影响火灾后土壤侵蚀和有机碳等元素的流动性。然而，在不同气候条件下，森林火灾后土壤有机碳化学成分的初始差异可能随着时间的推移逐渐减弱或扩大。土壤有机碳对野火的即时响应也会影响火灾后恢复过程中的生态系统响应和土壤功能。因此，记录火灾后有机碳化学的初始变化为研究气候如何影响火灾后的长期恢复提供了起点。测量气候对野火干扰对有机碳的影响需要一个良好的气候梯度，其中野火在研究地点同时发生，而生态系统变量保持相似。最近发生在夏威夷毛伊岛东部的野火提供了一个难得的机会来收集时间敏感的数据，以解决气候如何调节野火对有机碳化学的影响，因为燃烧区域与明确的气候梯度重叠，而且野火刚刚在2023年8月结束。鉴于这一宝贵但具有时效性的机会，迫切需要收集不同气候梯度的土壤样本。该项目的成果将通过网络研讨会与夏威夷牧场主分享，以制定基于科学的管理建议，帮助牧场主更好地为野火做好准备。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。

Soil organic carbon (SOC) largely determines soil health, functionality, and productivity. The accumulation of SOC can therefore contribute to climate change and is subject to alterations by wildfires, which are occurring with increasing frequency and intensity in the United States and across the world. Wildfires alter the chemistry and content of SOC in ways that affect SOC storage, soil erosion, and nutrient cycling. While wildfires occur under a wide range of climatic conditions, it is important to understand wildfire effects on SOC chemistry. The objective of this RAPID project is to address how climate influences wildfire disturbance in terms of the chemical composition of SOC. Soil samples will be collected across a rainfall gradient in Maui Island, Hawaii where wildfires occurred in August 2023. This project will have important implications for rangeland and forest management in Hawaii and beyond.Soil collection is required soon after wildfires to understand how wildfires affect SOC chemistry and soil properties. The initial chemistry of SOC after wildfire controls soil water repellency which directly affects post-fire soil erosion and mobility of SOC and other elements. However, the initial differences in the SOC chemistry after wildfires under different climates may fade or amplify with time during post-fire ecosystem recovery. The immediate responses of SOC to wildfire can also affect ecosystem responses and soil functions during post-fire recovery. Thus, recording initial alterations in SOC chemistry after wildfires provides the starting point for examining how climate affects long-term post-fire recovery. Measuring of the effects of climate on wildfire disturbances to SOC requires a well-constrained climate gradient where wildfires occur simultaneously across study sites while ecosystem variables remain similar. The very recent wildfires in eastern part of Maui Island, Hawaii provide a rare opportunity to collect time-sensitive data for addressing how climate modulates the impacts of wildfires on SOC chemistry because the burned areas overlap with a well-defined climate gradient and because the wildfire just ended in August 2023. Given this precious but time-sensitive opportunity, it is urgent to collect soil samples across the climate gradient. Outcomes of the project will be shared with Hawaiian ranchers through webinars to develop science-based management recommendations to assist ranchers to better prepare for wildfires.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.