Using visual obstruction to estimate heathland fuel load and structure

We present a simple non-destructive technique for assessing fuel load and critical aspects of vegetation structure that play important roles in determining fire behaviour. The method is tested in a Scottish Calluna vulgaris (L.) Hull heathland but could be applied to any vegetation up to ~1 m high. Visual obstruction of a banded measurement stick (the FuelRule) placed vertically through a stand of vegetation is governed by a combination of the height of the vegetation and its density. The vertical distribution of visual obstruction is calibrated to give estimates of total fuel loading, the loading of separate size categories and the vertical distribution and horizontal heterogeneity of fuels. The present paper provides a quick and simple method for estimating total aboveground biomass and structure that may be useful not just in studies of fire behaviour but where non-destructive assessment of biomass, vegetation density or canopy structure is needed. Calibration equations can be rapidly created for use in other vegetation or fuel types.