Prescribed burning is an effective and quick method to conserve rare pyrophilous forest‐dwelling flat bugs

Abstract

Abstract Fire suppression and reduced volumes of dead wood have led to a major decline in pyrophilous and saproxylic insects in Fennoscandian boreal forests. As a consequence, several species are currently seriously threatened. Flat bugs (Heteroptera, Aradidae) is an important invertebrate group that includes several pyrophilous species, including many threatened ones. We explored whether specific conservation measures – prescribed burning and retention forestry – can facilitate the survival of flat bugs in managed forests. The large‐scale field experiment consisted of a burning treatment (yes/no) and four levels of logging intensity (clear‐cut, retention levels of 10 and 50 m3 ha−1, and unharvested controls). The data included 1224 individuals of 12 species, sampled over a 4‐year period. Burning increased the species richness and abundance of the pyrophilous species. Two Red‐Listed and very rare pyrophilous species, Aradus angularis J. Sahlberg (Vulnerable) and A. laeviusculus Reuter (Near Threatened), were abundant after burning. The number of non‐pyrophilous flat bugs collapsed after burning but they re‐colonised the stands quickly, becoming as abundant as at the unburned stands. Logging increased the abundance of flat bugs only when retention forestry was applied. This study shows that pyrophilous flat bugs are quickly able to locate recently burned forests and that these forests are important for their survival. The effect of fire is, however, transient at the stand level and pyrophilous species disappear almost completely quickly after fire. To maintain these species, recently burned forests with a sufficient volume of retention trees should be available continuously at the landscape level.