Biotic response to forest harvesting in acidic blanket peat fed streams: A case study from Ireland

Blanket peat catchments are important biodiversity refugia and are increasingly recognised for their role in regional carbon and water balances. A key pressure on these catchments is forest clearfelling which increases stream phosphorus potentially leading to eutrophication. However, these unique systems are underrepresented in the development of bioassessment monitoring programmes and so are at risk to impacts. In this study, a multiple before-after-control-impact (MBACI) study was designed in three neighbouring peatland catchments and provided a unique opportunity to assess the impact of forest clearfelling events on macroinvertebrate and phytobenthic assemblages. Statistical analysis revealed substantial differences in the macroinvertebrate assemblages after clearfelling with higher abundances of chironomids. Macroinvertebrate derived indices EPT, diversity and species richness were significantly reduced. This was accompanied by a shift in functional feeding group representation away from shredders and collector-filterers to a dominance of collector-gatherers after clearfelling. In contrast, forest clearfelling did not significantly impact the diatom assemblages and diatom derived indices remained static for the duration of the study period.