The general location of Doire Bhraghad is shown in Figure 3.1, 3.4, and in local detail inFigure 3.7. The basin itself is shown in Figure 3.6 a and b. Doire
Bhraghad is located in Glen Lui. The mouth of Glen Lui joins Glen Dee at the Linn of Dee, and the head of the valley is connected via a low glacial breach to uppermost Glen Dee. Cairngorm Granite underlies the head of Glen Lui, but the Doire Bhraghad basin lies outside the granite pluton and is underlain by the Tormore Psammite Formation of the Dalradian Supergroup (Figure 3.2). Much of Glen Lui is underlain by Devensian till of unknown thickness, but Doire Bhraghad itself lies in an area of glacio-fluvial sand and gravel. The basin isthought to be a kettle hole and lies about 400m from the western side of the valley in a section of Glen Lui which runs north to south. The Lui Water is separated from Doire Bhraghad by about 250m of dry ground,
Figure 3.6a (above) Doire Bhraghad basin, looking west, April 2007 shows shallow water
on the east side of the basin. Figure 3.6b (below) detail of core site, August 2009 shows shallower water typical of late summer. The mire surface is usually driest in late May and June, over the last few years water has started to pond during July and August.
Figure 3.8 Doire Bhraghad basin morphology. Figure 3.7 Doire Bhraghad core site, purple spot, in a
up to 10m above the level of the river. The modern river bed is therefore slightly lower than the bottom of the mire.
The confluence of the Lui Water and River Dee is approximately 1km to the south of Doire Bhraghad. Together the valleys of the Lui and Dee form a roughly equilateral triangle. The Dee occupies one side; the Doire Bhraghad basin is towards the apex of the triangle. To the north of the basin the valley floor is flat and dry, lying up to 10m above the Lui Water. To the south the ground slopes gently towards the confluence of the rivers. The surrounding hills are up to 600m OD which may shelter the basin from prevailing winds; it is certainly the case that this part of Glen Lui tends to be less windy than the east-west trending valley of the Dee (author‟s own
observation during fieldwork). The closer western slopes are steeper than the valley sides on the eastern side of the valley, and today feature occasional Pinus within a Calluna heath. Doire Bhraghad takes its name from the extensive Pinus dominated woodland on the shallower eastern slopes.
Basin morphology was established in August 2008 and May 2009, using a 1m long, 2.5cm wide, Eijkelkamp gouge corer. Depth and stratigraphy were recorded at 2m intervals across the basin in east-west transects 5m apart. Peat depth within the basin is shown in Figure 3.8. The basin slopes above the mire surface are
asymmetrical, continuing the form shown by the peat in-filled section. The eastern and northern edges of the basin are steeper than the western edge; the southern side of the basin is level with the peat surface outside the basin. Ground surrounding the basin on the east, west and north is almost flat. There are no streams flowing into the basin, but there may be movement of water out of it southward either as dissolute surface flow or perhaps as ground water. To the south a small stream drains the hillside to the west towards the Linn of Dee through a series of surface pools.
As can be seen in Figure 3.6, the mire surface is now differentiated between a relatively dry area and a much wetter substrate, with the drier part up to 70cm higher. Vegetation on the mire surface includes two mature Pinus individuals, surrounded by Calluna, Vaccinium and Sphagnum. The deepest parts of the basin (Figure 3.8) are to the left of the extant pine trees growing on the surface of the mire (Figure 3.6). This part of the basin is crossed by (sub-fossil?) roots of Pinus and has three Pinus stumps. The core position is on the edge of the lower wetter section of the mire (Figure 3.6). During winter this part of the basin consists of shallow (up to 5cm deep) water (obvious in Figure 3.6); this dries out during the summer. Cyperaceae, Poaceae and Sphagnum grow on the margins of this section (Figure 3.6b).
Figure 3.9 shows the National Vegetation Classes for the area around Doire Bhraghad. NVC lists the west side of the Lui Water, around Doire Bhraghad as mire, with Pinus woodland on the eastern side of the river. The mire classification includes Calluna vulgaris-Vaccinium myrtillus heath (H12) and Erica tetralix-Sphagnum compactum wet heath (M16), within these are scattered Pinus, typically mature and veteran individuals. Southwards, towards the Linn of Dee, the gently sloping, rather wet, ground has occasionally dense patches of Pinus with some Betula and occasional Sorbus aucuparia. This area is fenced and is probably planted. A generally sparse understory includes Erica tetralix, Calluna vulgaris, Cyperaceae, Poaceae and ferns. To the north and west (upper Glen Lui) scattered Pinus woodland with Calluna gives way to Calluna heath.
The Doire Bhraghad mire is the deepest basin on the valley floor found in the Mar Lodge area and has the thickest sequence, suggesting a full Holocene sequence. Though the stratigraphy has very clear changes, it had the potential for high temporal
Figure 3.9 National vegetation classification near Doire Bhraghad core site (purple spot) courtesy of Scottish Natural Heritage, red circle
indicates the likely maximum relevant source area for arboreal pollen. Key to Legend A- aquatic, CG- calcicolous grassland, H- heath; M- mire; NA- not available, OW- open woodland, S- swamp and tall herb fen, U- calcifuge grassland and montane communities, W- woodland and scrub. Vegetation classification is incomplete in this area, in particular the large parrelogram, bounded by fencing, to
resolution analyses. The basin is slightly larger than ideal, but nonetheless pollen recruitment is principally from the valley floor. There are no inflowing streams to the basin, and it is separated from any influence from the main river. The maximum RSAP for arboreal pollen is shown in Figure 3.9 as between 300 and 400 metres, but this will have been lower during periods of closed canopy woodland. The basin is approximately 400m from the valley slopes (Figure 3.7 and 3.9), beyond the probable RSAP of most arboreal taxa. More poorly dispersed pollen is likely to have a pollen source area much smaller than that depicted.
The 1.92m deep core was sampled using a 1.0m long, 5.0cm diameter Russian peat corer in November 2002. The corer cannot sample the lowermost 9cm of a deposit due to its nose cone. At Doire Bhraghad it was thought that this basal sediment was not significant.