Pollen identification

Pollen analyses were made using a binocular Leica DM500 microscope.

Counts were made at magnification x400 with critical examinations made at magnification x1000 under oil immersion. Pollen was identified by reference to Moore et al. (1991) and the University of Stirling pollen reference collection. Counts were based on a minimum of 500 grains total land pollen (TLP) except for one level, 74.5cm, from White Bridge, where the count was 452 grains. Pollen nomenclature follows Bennett (1984) and plant nomenclature follows Stace (1991).

Some pollen taxa, for example Cyperaceae and Poaceae, are identified only to family level. Separation of Poaceae to cereal type groups follows Andersen (1979).

Separation of Corylus avellana and Myrica gale remains controversial. Edwards‟ (1981) scepticism is questioned by the separation of these by Moore et al. (1991) and particularly by Blackmore et al. (2003) and, with due caution by Punt et al. (2003). Three categories were erected in this study: (a) Corylus, (b) Myrica and (c) Corylus avellana type to include grains not positively identified as either. Separation of tree birch from Betula nana (Prentice 1981) was not attempted.

The second area of taxonomic contention is the separation of the tetrad pollen of the Ericales group, including Calluna vulgaris, Empetrum nigrum, Vaccinium type, Erica spp, Arctostaphylos, Pyrola type and Phyllodoce caerulea. Pollen of this group was determined to species level if possible using the special key in Moore et al. (1991, p88) and following Foss and Doyle (1988). In this group, Ericaceae undifferentiated are grains not placed in any higher taxonomic level. Table 3.1 provides details of features used during routine counting to identify grains. Terms used describe the features searched for during counting. They are often qualitative and subjective but can differentiate grains.

Some possible plants included within a pollen taxon, e.g. Erica ciliaris and Arctostaphylos alpinus can be excluded as outside likely latitudinal range. More careful consideration is required in the case of Empetrum nigrum ssp hermaphroditum and Phyllodoce caerulea, whose altitudinal ranges are now above all three sites. The controls on altitudinal limits are likely to have been considerably different in the past. It is also possible that Phyllodoce grains could be misidentified as Pyrola type (exits 6a and 6b Moore et al. 1991, p88) or Empetrum. Ledum palustre is an introduced species from North America and Corema album is not listed as part of the British Flora (Stace 1991). Pyrola type includes P. rotundifolia, P. media, P. minor and Moneses uniflora.

Table 3.1 Identification and categorisation of pollen

Pollen taxa Distinguishing features used during counting

Plant Possible mis-

identifications Corylus

avellana

Nexine and sexine continue right to the edge of the porus.

Corylus avellana: hazel Myrica gale Myrica gale Endoaperture larger than

ectoaperture

Myrica gale: bog myrtle Corylus avellana Corylus

avellana type

Not identified positively as Corylus or Myrica

Corylus avellana or Myrica gale

Arctostaphylos uva-ursi

Fairly large, globular tetrad with individual grains triangular obtuse, inner walls of tetrad slightly perforated Arctostaphylos uva-ursi: bearberry Arctostaphylos alpinus, inner walls more perforated, fewer endocracks

Calluna Tetrad in a single plane; coarse scabrae-verrucae-gemmae; tetrad and colpi rather irregular

Calluna vulgaris: Ling Heather Some Pyrola tetrads may be a single plane tetrad Empetrum nigrum ssp nigrum type

Small triangular obtuse tetrad; darker appearance due to thick inner walls; psilate or granulate surface Empetrum nigrum ssp nigrum/hermaphroditum: Crowberry. Corema album, Portuguese Crowberry Phyllodoce; Ledum palustre

Erica tetralix Mid sized globular to triangular obtuse tetrads, scabrate-verrucate surface, clear costae to the colpi

Erica tetralix: Crossed leaved heath. E. ciliaris, E. umbellata Costae may be less obvious, possible confusion with Vaccinium

Erica cinerea Large globular grain, colpi often widening toward equator, very distinct costae to colpi.

Erica cinerea: Bell heather

Some overlap with largest Vaccinium grains. Vaccinium Mid sized globular to triangular

obtuse tetrads; surface psilate- scabrate-verrucate; costae to colpi insignificant or absent.

Vaccinium spp: bilberries Some overlap with largest E. cinerea grains Phyllodoce Tetrad with short colpi with

indistinct outline; surface psilate to scabrate-verrucate surface; detectable costae; Phyllodoce coerulea: blue heath, Empetrum, Pyrola

Pyrola type Tetrad with short colpi with

indistinct outline, surface psilate to scabrate-verrucate; costae

detectable.

Pyrola sp: wintergreens. Moneses uniflora: one flowered wintergreen. Fine ornament on Calluna may appear to be Pyrola. Ericaceae undifferentiated

No positively identified features placing the grain firmly within other taxa.

Mainly Calluna, with obscured or hidden Erica spp, Vaccinium and Empetrum

Pyrola type in Mar Lodge is most likely to include Pyrola spp, as Moneses uniflora is a lowland species found up to 300m only (Preston et al. 2002).

During counting pollen was assessed for deterioration and assigned into one of five categories: normal, crumpled or folded, split or torn, corroded, and degraded. Following Lowe (1981) and Tipping (1987), Indeterminate pollen was assigned to five categories: hidden, crumpled, split, corroded and degraded, indicating the reason for lack of identification.

Pinus stomata were counted as part of the routine count. Identification was made using pictures from Trautmann (1953) and Hansen (1995) and a dichotomous key from Sweeney (2004). In samples from the minerogenic band at Doire Bhraghad further stomata counts were made based on exotic counts only. Stomata in levels 114- 100cm from Doire Bhraghad were counted to a pollen equivalent of 2500-4000 grains. Fungal and algal material was also counted, and in some cases identified (van Geel, 1978), providing information of bog surface conditions. Diatoms were counted and can be used to infer surface wetness of peat of sub-samples not treated with HF. Microscopic charcoal was divided into five size classes (10-25m, 25-50m, 50-75m, 75-100m and >100m) to provide evidence of vegetation burning

(Cayless and Tipping 2002). In addition to these size classes, pieces of charcoal with a long axis of more than 150m were encountered within the first pollen count, despite sieving at 150m during pollen preparation. Systematic counting of large charcoal particles was not initially planned but these were subsequently noted. These largest microscopic fragments have been shown by Clark (1988), Clarke and Royall (1993) and Higuera et al. (2005) to be associated with fires within 100m of a site. Higuera et al. (2005) showed that not all local moderate to low severity fires were detected using

charcoal larger than 125m, but fewer false positives were found compared with macroscopic charcoal (larger than 500m).

Pollen diagrams were drawn using Tilia software (Grimm 1993). All taxa are shown in percentage diagrams (Figures A.1a, A.2a, A.3a), but only principle

contributing taxa are shown in concentration (Figures A.1b, A.2b, A.3c), and influx (Figures A.1c, A.2c, A.3c) diagrams.

4 Doire Bhraghad: results and interpretation

4.1 Introduction

The results and the interpretation of the results from the Doire Bhraghad core are presented here. Data including sediment descriptions and morphology,

colorimetric data, percentage loss of mass on ignition (LOI) and radiocarbon assays are presented in Section 4.2. Descriptions of local pollen assemblage zones are presented in Section 4.3.1 and results of rarefaction analysis (palynological richness) are presented in Section 4.3.2. Dating models and pollen influx data are presented and described in Section 4.4. Interpretations of the Doire Bhraghad data form the final section of this chapter (Section 4.5). All pollen diagrams are presented in Appendix A.1.

4.2 Sediment description and morphology, colorimetric data, percentage