Thursday, May 17, 2012

Forestry Management for Caddisfly Biodiversity

Philopotamus montanus
With around 8% of Ireland under commercial forests (1), correct management of these sites is essential to maintain biodiversity in a variety of habitats throughout the country. Most commercially forested sites are in uplands, where the nature of the soils make them unsuitable for dairy or beef production. Being in upland areas they will inevitably have streams near or often running through them. The vast majority of these commercial forests in Ireland are coniferous which have been shown to directly influence the ecology of forest streams through hydrological, chemical and energetic pathways (2), so the layout of the forests upon planting is very important.
Philopotamus montanus
An engaging little caddisfly that is often found associated with coniferous forest streams is Philopotamus montanus. The larvae live in fast moving streams, spinning long, tubular, bag-like nets on the undersides of rocks which they use to catch diatoms and detritus (3). The clumsy, slow flying adults rarely venture far from these streams and are on the wing from May to August (however the individuals pictured were photographed in April). However the occurrence of P. montanus in forest streams is very much dependent on its management. Specifically, it requires small rocky streams with hard margins (2). Therefore it is essential to take these needs into account when laying out commercial forests near streams if we are to keep these little brown and yellow winged wonders for the future.
Philopotamus montanus
  2. Weatherley et al., 1993. Biological Conservation 63 171-176
  3. Gibbons, 2010. Insects of Britain and Europe p. 143

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