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

Abstract

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.