The impact of moorland cutting and prescribed burning on early changes in above-ground carbon stocks, plant litter decomposition and soil properties

Abstract

Prescribed burning is a common method of vegetation management globally, yet there are growing concerns around its impacts on carbon emissions, nutrient cycling and soil functioning. Heather (Calluna vulgaris (L.) Hull) moorlands are managed by burning, yet cutting heather represents an alternative management technique increasingly implemented by land managers. Current evidence remains limited on the effects of burning compared with different cutting techniques on carbon and nutrient cycling. This study compared the initial effects of burning moorland vegetation and two different methods of heather cutting—robotic cutting and brush cutting—on plant carbon stocks, plant litter decomposition rates and soil properties at two heather-dominated moorland sites in north-east Scotland, UK. As a moorland vegetation management technique, burning was the only treatment to significantly reduce total vegetation carbon (by 53% or 0.58 kg C m−2) compared with controls without any interventions. Both cutting treatments, brushcutting and robocutting, resulted in significant reshuffling of plant carbon pools. Cutting increased cut heather, moss and litter, but reduced coarse plant carbon remaining on living heather shrubs. Brushcutting and burning removed fine plant carbon remaining on heather. In the short term (5 months), robocutting and burning accelerated labile and recalcitrant plant litter decomposition compared with controls. Longer-term litter decomposition (12 months) measured using wooden sticks did not significantly differ between treatments. There were no significant treatment differences in available soil nutrients or soil temperature. Practical implications: From our study, it is unclear whether cutting is a good replacement for burning in minimising vegetation and plant litter-based carbon losses in the short term. Our results suggest the heather cutting method can influence rates of plant litter decomposition, with brushcutting resulting in the smallest changes in decomposition compared with robocutting and burning. Based on our results, areas of future research would be longer term monitoring of impacts of burning and cutting techniques on heather regrowth, below-ground carbon storage and wildfire risk. For the latter, cutting transferred attached fine heather material to litter, which could serve as ignition sources for wildfires, whereas these fine fuels were not transferred to litter and reduced following burning.