Variation in the woodland cover of the Morar Basin, with particular reference to the palaeolimnology and palaeomagnetic record from Loch Morar, Highland Region, Scotland.

Abstract

This thesis examines aspects of the palaeolimnological and palaeomagnetic records from Loch Morar, Highland Region, Scotland. The palaeoecological interpretation of these records is augmented by a review of the floristic character of the current vegetation. Palaeomagnetic data from a long core display secular variations of declination and inclination for an unknown time interval. The top metre has been compared with records from northwest Europe covering the last 10,000 years and has been tentatively assigned to that time interval. A preliminary pollen analysis appears to confirm this interpretation. Stabilization of terrain is indicated by declining magnetic susceptibility, coupled with constant sediment accumulation rates during the period represented by the top metre of the sediment core. The fossil diatom record from the same provides an insight into the tophic status of the lake and catchment areas, suggesting significant acidification during the Holocene Period. Iron Oxide deposition suggests a widespread development of waterlogged soils during the same period. A qualitative examination of woodland sites within the catchment area indicates that relict native oak (Quercus petraea x robur) and birch (Betula pubescens ssp. odorata) woodland, referable to the Betuletum Oxaleto-Vaccinetum and Betula-herb noda, survives at several sites around Loch Morar, and that native Scots pine (Pinus sylvestris var. scotica) woodland, referable to a combination of the Pinetum Hylocomieto-Vaccinetum and Pinetum Vaccineto-Callunetum association, occurs on an archipelago in the loch. The presence of Pinus sylvestris var. scotica at this site suggests that the geographical distribution range of this taxon extends farther westwards in mainland Scotland than previously recorded. A phytosociological study of the epiphytic (corticolous) lichen flora previously record from these woodland sites by Dr Francis Rose, and the application of the Revised Index of Ecological Continuity sensu Rose (1976) indicates that they have experienced ecological continuity of high tree cover, as opposed to coppice, over a long period.