Background: Fuel moisture content (FMC) is a critical component of wildfire risk. The spatiotemporal patterns of FMC of many key temperate fuels (e.g. heather, gorse, bracken, moor grass, litter, organic soil layer) are largely unknown and unravelling the drivers of FMC is challenging. Current models designed to predict FMC, principally of dead fuels, generally consider only weather variables. However, landscape factors affect water retention and availability of moisture within soils, and are likely to influence FMC of live and organic ground fuels. We investigate the potential effects of landscape factors on FMC. We carried out a large-scale fuel sampling campaign from 2021–2023 of eighteen different fuel types across 43 sites through five different climate regions of the UK. We implemented boosted regression trees to determine the influence of fifteen variables on FMC, which included weather, temporal, and landscape data.
Results: We found that landscape influences FMC, particularly for the organic ground fuels, live bracken and live moor grass. Dead fuels were generally influenced least by landscape factors. The predictive ability of our models was good (mean correlation between predicted and observed FMC of > 0.5) in twelve of eighteen fuels and for most fuels, including landscape factors increased the variance in FMC explained. Predictive ability was greater in models including landscape factors (compared with models just containing weather and temporal variables) for live fuels, litter and the organic layer. For dead fuels, moss and twigs, including landscape factors did not increase the models’ predictive ability.
Conclusions: We have shown that landscape factors are important to consider when developing fuel moisture models, but that this is mainly important for live fuels and organic ground fuels. We therefore recommend tailoring models to each fuel type to yield the best performance.