In upland Britain, conifer plantations are a major land use and influence stream ecosystems. This paper evaluates the effects of four types of plantation management for the conservation of stream macroinvertebrates across 66 sites in Scotland and Wales.
Sixty-six upland streams were selected representing different land uses or forest management:
1) CON sites - mature conifers up to the stream edge;
2) CLR sites - conifers clear-felled in a ‘buffer strip’ on both stream sides;
3) MOR sites - unplanted moorland buffer strips or entirely moorland;
4) BRD sites - broadleaf tree buffer strips or entirely broadleaf woodland.
During October-November 1990, within stream riffles and margins, invertebrates were collected during 2 minute kick samples and physical habitat structure was surveyed.
Representaives of six families (Nemouridae, Leuctridae, Polycentropodidae, Limnephilidae, Tipulidae, Chironomidae) and Oligochaeta were collected at more than 80% of sites; a further 18 other ‘groups’ (including 10 families; Tricladida and Mollusca) occurred at five or more. Stream acidity (not significantly different between management groups) was the prevalent factor influencing taxon occurrence. As acidity increased, nine families and Mollusca were significantly less frequent (the influence of acidity on these is well known).
Marginal habitats were related to management (within stream habitats less so); CON and BRD streams tended to have rocky margins with tree roots, MOR streams had most vegetated margins; CLR streams were intermediate. Despite the prevailing influence of stream acidity, a number of taxa were influenced by management/habitat features.
The highest number of invertebrate families were usually recorded at MOR sites, were intermediate at CLR and BRD sites, and CON sites had lowest abundances (around12 families). Leptophlebiidae (mayflies), Dytiscidae and Hydrophilidae (beetles) had a preference for soft marginal habitats (normally scarce in forest streams). Perlidae (stoneflies), Helodidae (beetles) and Philopotamidae (caddisflies) favoured hard margins and tended to be most abundant in BRD streams. Few differences in abundance between management groups were significant at species level. The authors suggest that various forestry management techniques should be practised to provide a variety of stream habitat types.
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