Leaving moss and litter layers undisturbed reduces the short-term environmental consequences of heathland managed burns

Roger Grau-Andrés,G Matt Davies,Susan Waldron,E Marian Scott,Alan Gray

doi:10.1016/j.jenvman.2017.08.017

Abstract

Variation in the structure of ground fuels, i.e. the moss and litter (M/L) layer, may be an important control on fire severity in heather moorlands and thus influence vegetation regeneration and soil carbon dynamics. We completed experimental fires in a Calluna vulgaris-dominated heathland to study the role of the M/L layer in determining (i) fire-induced temperature pulses into the soil and (ii) post-fire soil thermal dynamics. Manually removing the M/L layer before burning increased fire-induced soil heating, both at the soil surface and 2 cm below. Burnt plots where the M/L layer was removed simulated the fuel structure after high severity fires where ground fuels are consumed but the soil does not ignite. Where the M/L layer was manually removed, either before or after the fire, post-fire soil thermal dynamics showed larger diurnal and seasonal variation, as well as similar patterns to those observed after wildfires, compared to burnt plots where the M/L layer was not manipulated. We used soil temperatures to explore potential changes in post-fire soil respiration. Simulated high fire severity (where the M/L layer was manually removed) increased estimates of soil respiration in warm months. With projected fire regimes shifting towards higher severity fires, our results can help land managers develop strategies to balance ecosystem services in Calluna-dominated habitats.

Highlights

The severity of a fire was defined by Keeley (2009) as the direct, immediate fire effects such as degradation and loss of organic matter
We investigated the effect of variation in ground fuel structure on fire-induced soil heating using linear mixed effects models that included an interaction between treatment (M/L layer present and removed) and depth of measurement as fixed effects and fire as a random effect
As measured by total heat, maximum temperature and time above 50 C, was higher in plots where the moss and litter (M/L) layer had been removed prior to the fire than in those where it was present during the burn (Table 2)

Summary

Introduction

The severity of a fire was defined by Keeley (2009) as the direct, immediate fire effects such as degradation and loss of organic matter. Altered post-fire environmental conditions include loss of nutrients (Rosenburgh et al, 2013), substrate change due consumption of ground fuels, e.g. the moss and litter (M/L) layers, during high severity fires (Davies et al, 2010), and changes to post-fire soil microclimate resulting from loss of vegetation cover (Mallik, 1986; Brown et al, 2015) The latter is important as microclimate is a control on soil respiration and soil carbon dynamics (Lloyd and Taylor, 1994; Kettridge et al, 2012; Walker et al, 2016). Where ecosystems have peat or thick organic soils, the ignition of these during extremely severe fires can have considerable consequences for carbon storage and ecological function (Maltby et al, 1990; Davies et al, 2013; Turetsky et al, 2015)

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