EFFECTS OF LIMING ON THE COLEOPTERA, HEMIPTERA, ARANEAE AND OPILIONESOF CATCHMENT WETLANDS IN WALES

The liming of hydrological source areas in stream catchments has been increasingly proposed for treating the symptoms of surface water acidi fication. Here, we assess the effects on terrestrial invertebrates in upland mires in Wales by comparing assemblages at three limed sites wi th 10 unlimed reference sites. The Veliidae (Heteroptera) and Hydrophi lidae (Coleoptera) were significantly more abundant, while the Carabid ae were significantly less abundant at limed sites. Over 50% of 113 be etle species occurred at single sites. Among spiders, the Lycosidae we re significantly less abundant at limed sites whereas the Linyphiidae and Tetragnathidae were less abundant at unlimed sites. None of these significant effects could be ascribed to differences in other measured attributes of the sites other than liming. At the community level, th ere were no gross differences between limed and unlimed sites shown by rank-abundance curves or diversity indices. However, assemblages at l imed and unlimed sites were clearly differentiated by ordinations on s pider families, carabid species and all beetle species. Qualitative di fferences of this type were more closely related to liming than to any other factor. Further studies are required to assess whether these co rrelations between lime additions and invertebrate assemblages are cau sal. In the meantime we advocate caution over lime additions to upland mires, particularly when important invertebrate assemblages are known to occur. Copyright (C) 1996 Published by Elsevier Science Limited