The impact of muirburning on lichen diversity
Davies, G. Matt
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The use of fire as a management tool on moorlands is a practice with a long history. Primarily carried out to maintain a monoculture of young, vigorous growth Calluna to provide higher quality grazing for sheep, deer and grouse muirburning has a profound effect on the ecology and species composition of moorlands. The overriding influence on the ecology of heathlands is the life-cycle of Calluna vulgaris from the early pioneer phase through the building and mature phases to the degenerate phase. Lichen diversity is largely controlled by the life cycle of C. vulgaris. The process of burning interrupts the natural life cycle of Calluna preventing it moving into the mature and degenerate phases. From the early building phase onwards Calluna begins to greatly influence the microclimate below it canopy creating darker, moist conditions which favour the growth of pleurocarpous mosses over lichens and sees the latter largely replaced with the exception of a few bryophilous species. Muirburning largely aims to prevent progression to the mature and degenerate phases and thus to period traditionally seen as of high lichen diversity. However it maintains areas free from the overriding influence of Calluna where lichens may be able to maintain higher diversity than beneath the Calluna canopy. One hundred quadrats were completed on the moorlands of the National Trust for Scotland Mar Lodge Estate with the aim of quantifying and explaining changes in lichen diversity. 37 different burns were investigated as well as 26 unburnt sites. Analysis of the data was carried out using regression analysis and DCA. The results indicate that lichen diversity increases following burning but declines underneath the closed Calluna canopy. Mats of pleurocarpous mosses largely replaced lichens in older stands with only corticolous species showing any increase in this phase. There exists however significant differences between different communities with lichens in the second area studied being both more diverse and maintaining their abundance into the building phase, the drier conditions allowing them to fill the niche normally held by pleurocarpous mosses. Key factors in controlling lichen diversity were shown to be the time since fire and soil moisture although the latter may be linked to the changing dominance of Calluna and the influence of its microclimate.