Changes in peat chemical properties during post-fire succession on blanket bog moorland

Abstract

This study assessed the impact of prescribed burning on the peat properties of moorlands during the post-fire succession in a multi-site study within a major moorland region of Great Britain. Three replicate moorland sites were sampled; all were ombrotrophic bogs and had peat soils overlying similar geology and similar vegetation. A chronosequence approach was used to sample soils from a post-fire succession (3–52years since burning) on each site and a number of chemical properties measured. The data on soil chemical properties were analysed using both linear-mixed-effects modelling and multivariate analysis. There were clear differences in some soil properties between moorland sites, but for most soil variables measured there was no change through the post-fire succession. Four variables (available P and Ca; total P and K) showed a significant interaction, i.e. different responses on each moorland site through time. These results suggest that there are complex interactions between nutrient inputs (rainfall and dry deposition which is affected by elevation), storage and cycling within the soil-peat system and losses that differ on the three moorland sites. The most interesting result was the additive response of the C:N ratio which differed between moorland sites; all sites showed the same negative slope with respect to elapsed time since burning, indicating an increased N saturation. This result suggests that the oldest stands sampled here may have either (i) responded to the large N inputs added from the atmosphere in the latter part of the twentieth century, or (ii) the younger ones have had some of this N removed during prescribed burning. This suggestion needs further investigation. Nevertheless, the impacts of prescribed burning on the peat properties during the post-fire succession were relatively small.