Table 1 The hypothesized landscape drivers of fuel moisture variability examined for plot selection. We classified landscape drivers using the provided sources and validated these with field assessments
From: Landscape controls on fuel moisture variability in fire-prone heathland and peatland landscapes
Driver | Classification (number of sites in each classification, n = 36 sites) | Source | Significance (hypothesized from previous research) |
|---|---|---|---|
Soil texture | Coarse: Freely draining very acid sandy and loamy soils (12 sites) Fine: Slightly acid loamy and clayey soils with impeded drainage; slowly permeable seasonally wet acid loamy and clayey soils (12 sites) Peat: Blanket bog peat soils and slowly permeable wet very acid upland soils with a peaty surface (12 sites) | Soilscapes class numbers (Farewell et al 2011) | Soil texture captures the soil hydraulic traits (e.g., soil depth, porosity, permeability, drainage flow paths, and water table depth) hypothesized to control water availability to dead fuels via capillary action and live fuels via water uptake by roots (Nyman et al 2015; Matthews 2014) |
Canopy age | Building: 5–10 years since last burn, 30 cm height (18 sites) Mature: 15–20 years since last burn, 60 cm height (18 sites) | Land managers’ records and satellite imagery | Fuel age and height influence fuel moisture by creating differences in shading, fuel structure, and plant hydraulic traits. Live fuel canopy cover and biomass have been shown to regulate the moisture content of underlying fuels (Nyman et al 2018; Brown et al 2022b). But also within the same species, variability in biomass, age, and the proportion of live-to-dead material influence the moisture content of live fuels themselves (Davies and Legg 2011; Brown et al 2022a) |
Hillslope position | Low: low plateau (12 sites) Medium: mid-slope (12 sites) High: high plateau (12 sites) | OS Terrain® 50 DTM OS data © Crown copyright and database right 2022 | Hillslope position influences drainage flow paths across the landscape and thus the availability of water to live fuels (Tromp-van Meerveld and McDonnell 2006) |
Aspect | North (18 sites) South (18 sites) | OS Terrain® 50 DTM OS data © Crown copyright and database right 2022 | North and south aspects capture the range of variation in incoming solar radiation to dry out fuels. Topography and aspect influence fuel moisture through the formulation of complex microclimates that modify the meteorological controls on drying (humidity, temperature, windspeed) (Nyman et al 2015, 2018; Brown et al 2022b). Dead fine fuels are typically drier on equatorial than polar facing slopes (Nyman et al 2015; Walsh et al 2017; Slijepcevic et al 2018) where spatial differences driven by variations in incoming solar radiation between polar and equatorial facing slopes are created |