The faunal communities of upland streams in the eastern region of Ireland with reference to afforestation impacts

Macroinvertebrates were sampled from forty-seven sites on upland soft water streams in eastern Ireland. Classification generated four recognisable fau nal communities or site groups which differed in biological, physical and c hemical character; these patterns were supported by ordination analyses. Th e environmental gradients which probably influenced water quality were broa dly categorised into geology, distance from source or elevation and forestr y. Faunal diversity and abundance were reduced in both high altitude and ex tensively afforested sites compared to moorland sites. Whereas, Plecoptera dominated the fauna at most sites, many taxonomic groups such as the Epheme roptera and members of the family Elmidae were absent from high altitude an d forested areas. The impact of afforestation was most evident at those sit es which were located in forest plantations or were on catchments with exte nsive (>25%) closed canopy (>12 yr) afforestation. Low levels (<25%) of for estry in the absence of acid waters did not lead to impoverishment. This wo rk reveals how plantation forestry in areas receiving only moderately pollu ted rain can be linked with acid waters and impoverished invertebrate commu nities.