THE LATE DEVENSIAN VEGETATIONAL HISTORY OF THE WHITLAW MOSSES, SOUTHEAST SCOTLAND

Abstract

SUMMARYLate Devensian Late‐glacial deposits are described from the Whitlaw Mosses, near Melrose, Roxburghshire (now Borders). Pollen diagrams and macro fossil lists are given for the bottom sediments of Beanrig Moss and Blackpool Moss, two small fens lying in hollows in the undulating boulder clay of Tweeddale. The succession of taxa through the sediments indicates interstadial conditions followed by stadial conditions.Critical determinations of certain microfossil and macrofossil indicator taxa, permits the identification of certain plant communities. These are as follows: Communities identified from within the stadial are;(1) bare‐ground communities of open, wind‐exposed areas with Artemisia cf. norvegica and Papaver spp. of the section scapiflora as the main indicator types;(2) bare‐ground communities in sheltered areas of long snow‐lie with such species as Salix herbacea, Polytrichum norvegicum and P. alpinum.The main communities identified in the interstadial are as follows:(1) scrub with abundant Juniperus and sparse tree birches (e.g. B. pubescens);(2) base‐rich, well‐drained short turf with abundant Helianthemum;(3) damp, tall‐herb meadows in which Rumex acetosa is important;(4) dwarf‐shrub heath with Dryas octopetala and Betula nana;(5) open‐ground communities with Artemisia spp. and Hippophaë.Communities identified from both the stadial and interstadial are:(1) short‐turf calcareous flushes or springs with Selaginella and various mosses;(2) fens and marshy lake margins with, e.g. Homalothecium nitens.Several taxa have not hitherto been found in the Late Devensian of the British Isles, amongst which are Artemisia cf. campestris, A. sect. dracunculus, A. cf. maritima s.l., Gypsophila repens/fastigiata, Hedysarum cf. hedysaroides, Minuartia rubella, Rhacomitrium cf. canescens and Vactinium vitis‐idaea. The identification of the pollen grains and macro fossils is discussed and comments are made on the biogeographical and ecological implications of the records, especially of those species which are now no longer part of the British flora.