Fuel moisture content of vegetation in the UK, 2021-2023, measured as part of UK Fire Danger Rating System

Data were collected by sampling vegetation. The sampler established 20 m transects at sample sites and collected samples between 11:00 and 17:00 local time. For heather, gorse and bracken, stems and either canopy (heather, gorse) or leaves (bracken) were sampled separately, and for all vegetation both live and dead samples were taken. Live moss samples were collected by pinching the top two cm of moss from the soil surface, and litter samples were collected by pinching the top two cm of dead leaf litter from soil surface, at ca. 10 points along the transect. These two fuel types were sampled separately, and if both occurred together the constituents were separated. For the organic layer, defined as the organic material beneath the surface litter and above the mineral soil, the top 5 cm of soil was sampled at four points along the transect. In forested sites, twigs (<5 mm diameter) were collected from fallen branches at ca. 10 points along the transect. Only those which were not in contact with the floor were collected. The same fuel constituents sampled along the transects were combined within aluminium screw-fit tins that were sealed with masking tape. Gravimetric fuel moisture content (FMC) was calculated by weighing the collected samples, drying them for 48 h at 80 °C and then reweighing the dried samples. The FMC is calculated as:
(W - D)/(D - T) * 100
where W = wet weight (g), D = dry weight (g) and T = the weight of the sample tin (g).