Original paper
The impacts of acid precipitation mediated by geology and forestry upon upland stream invertebrate communities
Ventura, Marc; Harper, David
Archiv für Hydrobiologie Volume 138 Number 2 (1996), p. 161 - 173
42 references
published: Dec 4, 1996
DOI: 10.1127/archiv-hydrobiol/138/1996/161
ArtNo. ESP141013802001, Price: 29.00 €
Abstract
Macroinvertebrate assemblages and a number of physico-chemical parameters were measured during July 1993 in four southern Scottish upland headwater streams, two adjacent pairs, in the same area of Dumfries and Galloway impacted by acid precipitation. One pair of streams rose on a granite geology and the other pair on greywackes. One stream of each geological pair had an afforested catchment while the other rose in moorland vegetation. The granite streams had acidic pH (4.9), and the greywacke were circumneutral (pH 7.6). Ca2+, Mg2+, K+ were significantly lower and Al3+/sup> significantly higher in the two acid streams, irrespective of land use. The acid afforested stream had higher concentrations of all cations than the acid stream with moorland vegetation. Both afforested streams had higher concentrations of Na+ and Al3+, and lower temperatures, than the two with moorland vegetation. The two acid streams had lower taxonomic richness, higher percentages of Plecoptera and no Ephemeroptera, with higher percentages of predators and lower percentages of collectors than the circumneutral ones. Compared with the moorland pair, both afforested streams had higher proportions of shredders. Canonical ordination analysis (DCCA) showed acidity as a clear gradient dominating the first axis, with a less clear gradient reflecting the effect of coniferous plantations dominating the second axis. Gammarus pulex and Odontocerum albicorne were most strongly correlated with high pH, while Plectrocnemia geniculata was positively correlated with afforestation and low pH. The results confirm the impact of acid precipitation on stream communities lying on sensitive geologies but emphasise the localised scale of such impacts where geology changes. They also show the fundamental role of land use in influencing macroinvertebrate community composition.
Keywords
afforestation • conifeous • greywackes • granite • moorland • taxonomic • circumneutral