Climate change increases the frequency and intensity of vegetation fires around the world. Fire can considerably increase the landscape’s vulnerability to flooding and erosion, which is in part caused by fire-induced soil damage and hydrological changes. While it is known that plants can alter the fire environment, there is a major knowledge gap regarding the fundamental mechanisms by which vegetation mediates fire impact on soil physics and hydrology. I addressed this gap by considering for the first time the cascading effects of plants on fire and soil hydrology, focusing on two important factors in post-fire hydrology: soil heating and ash. My hypothesis is that plant structural and chemical traits vary within the landscape and control fire impact on soil physical properties by affecting heat and ash production. I tested this hypothesis with a combination of spatial sampling, lab experiments and modeling, using contrasting plant species and soils from watersheds in Portugal and the Navajo Nation (USA). Results indicate that plant flammability traits vary in the landscape, with implications for both soil heating and ash. I found that ash production and size is highly affected by the duration of smouldering combustion, and that loosely packed fuels (like standing fuels) therefore produce coarser ash than more densely packed fuels like litter beds. Within these fuel types, both plant species and fuel moisture content were important controls. These findings can help predict and mitigate fire risk and impact across landscapes, facilitate development of risk maps, and generate knowledge with implications for nature conservation, land use planning, fire management, safeguarding of water quality, and potential policy making. The training and research opportunities provided by this project changed a European braindrain into a braingain, supporting reintegration of a successful interdisciplinary scientist and her large network after three years in the USA. Through this reintegration I have been able to: 1) build my European network of interdisciplinary and intersectoral collaborators, 2) conduct original and innovative interdisciplinary research, 3) secure a permanent position as a tenured Assistant Professor at a leading European University, and 4) solidify my science communication and outreach by working with highly respected national and international media as well as with local and indigenous communities. As such, Marie Curie funding has opened up both a novel research line as well as the basis for new interdisciplinary and intersectoral collaborations in the soil and fire sciences which this summer has showed is highly needed in this changing climate.
