Assessing soil heating beneath prescribed burns undertaken by teams according to the first UK vegetation fire standards

Background Prescribed burning (PB) has been used on UK heathlands for centuries, with controversy over its potential to heat organic-rich soils. In recent years accredited training has been available to UK land managers providing them with improved skills with which to burn safely. Aims We assessed the levels of soil heating beneath PBs undertaken by these upskilled teams and provide an assessment of a range of burns using the same methodology at each burn. Methods In-field measurements of soil (3 cm depth), above-ground temperatures and fire severity assessments were taken during eight PBs across the UK, conducted under mild weather conditions and complying with PB guidance. Key results Both organic-rich peaty soils and mineral soils received little heating during the PBs tested, with mean maximum soil temperatures of <43.4°C, and surface mean maximum temperatures of 784.5°C. Fire severity assessments indicated no below-ground organic matter loss. Conclusions When following new accredited training, and according to Department for Environment, Food and Rural Affairs current guidance, underlying soils were not subjected to high temperatures that could directly damage long-term carbon stores. Implications Our results provide valuable insights into soil temperatures reached during PBs, highlighting that well-planned fire can be used safely in respect to burning vegetation particularly over organic-rich peaty soils.