Bryophyte recolonisation of burnt ground with particular reference to Funaria hygrometrica

Abstract

Field studies throughout England showed that the pattern of bryophyte recolonisation on a burnt site depends largely on the type of fire from which the site results. Two types of fire were distinguished, rapid fires and bonfires, these differing mainly in the amount of ash deposited and the duration of high temperatures, both being greater during a bonfire. On bonfire sites, after an initial period of growth inhibition, Funaria hypgrometrica characteristically became abundant, whilst scattered shoots of Bryum argenteum, Ceratodon purpureus and tuberous species of Bryum were often found. Then, as the angiosperm cover increased these pioneer mosses were replaced by the pre-burn species. Rapid fire sites in contrast, were colonised largely by species characteristic of the pre-burn vegetation, these only becoming abundant when angiosperm recolonisation was slow. Culture on inorganic nutrient agar showed that in the presence of adequate amounts of potassium and particularly phosphorus, growth of Funaria was stimulated by raising the level of nitrate nitrogen and soil analyses indicated some correlation between these requirements and. conditions in bonfire soils. Addition of inorganic nutrients to unburnt soil however, did not stimulate growth. Thus under natural conditions soluble organic nutrients, present in high concentrations in bonfire soils, may be essential for growth, or alternatively a heat-labile inhibitor may prevent good growth of Funaria on unburnt soil, though this seems unlikely. The excessively high concentrations of soluble substances found immediately after burning, together with the inhibition of nitrification, would explain the initial growth inhibition on bonfire sites, whilst the later disappearance of Funaria from bonfire sites could be linked with the gradual return of nutrient conditions to the pre-burn state and increasing angiosperm competition.