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

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.