Accounting for among-sampler variability improves confidence in fuel moisture content field measurements.

Background: Direct fuel moisture content measurements are critical for characterising spatio-temporal variations in fuel flammability and for informing fire danger assessments. However, among-sampler variability (systematic differences in measurements between samplers) likely contributes to fuel moisture measurement variability in most field campaigns. Aims: We assessed the magnitude of among-sampler variability in plot-scale Calluna vulgaris fuel moisture measurements. Methods: Seventeen individuals collected samples from six fuel layers hourly from 10:00 hours to 18:00 hours. We developed mixed effects models to estimate the among-sampler variability. Key results: Fuel moisture measurements were highly variable between individuals sampling within the same plot, fuel layer, and time of day. The importance of among-sampler variability in explaining total measured fuel moisture variance was fuel layer dependent. Among-sampler variability explained the greatest amount of measurement variation in litter (58%) and moss (45%) and was more important for live (19%) than dead (4%) Calluna. Conclusions: Both consideration of samplers within the experimental design and incorporation of sampler metadata during statistical analysis will improve understanding of spatio-temporal fuel moisture dynamics obtained from field-based studies. Implications: Accounting for among-sampler variability in fuel moisture campaigns opens opportunities to utilise sampling teams and citizen science research to examine fuel moisture dynamics over large spatio-temporal scales. Citizen science provides an important opportunity for the wildfire community, enabling data collection at broad spatio-temporal scales. Direct fuel moisture measurement campaigns can maximise these benefits by accounting for natural differences in measurements between individuals. We quantify the magnitude and variability of differences during an intensive fuel moisture measurement campaign. [ABSTRACT FROM AUTHOR]