|
|||||
|
|
Macro-floral assemblages in upland Welsh streams in relation to acidity, and their importance to invertebrates |
|
| Authors: | S J ORMEROD K R WADE A S GEE† |
| Institution: | Department of Applied Biology, University of Wales, Institute of Science and Technology, Curdiff, and Welsh Water, Penyfai House, Llanelli, Dyfed;Welsh Water, Tremains House, Coychurch Road, Bridgend, Mid Glamorgan;Welsh Water, Hawthorn Rise, Haverfordwest, Dyfed |
| Abstract: | SUMMARY 1. Macro-flora (angiosperms. bryophytes and macroscopic algae) and macroinvertebrates were sampled in 1984 at eighty-eight sites on soft-water streams in upland Wales. Assemblage patterns were related to stream chemistry using TWINSPAN, DECORANA and multiple discriminant analysis. 2. Floral assemblages could be related most strongly to pH and aluminium concentration, with Scapania undulata, Nardia compressa and filamentous chlorophytes characterizing streams of mean pH5.2–5.8, whilst Fontinalis squamosa occurred mostly at pH 5.6–6.2 and Lemanea at pH 5.8–7.0. We propose an indicator system based on thesetaxa. 3. Assemblages of invertebrates and flora concorded highly significantly, sites with Scapania and Nardia holding impoverished faunas. Because some acid sensitive invertebrates (e.g. Ecdyonurus and Ancylus ) can feed from acid tolerant plants (e.g. Scapania ), we hypothesize that they are restricted physiologically from acid streams. |
| Keywords: | |