POLLEN DIAGRAMS FROM SOUTHERN ENGLAND: ELSTEAD, SURREY

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1 POLLEN DAGRAMS ROM SOUTHERN ENGLAND: ELSTEAD, SURREY BY S. C. SEAGRE* AND H. GODWN University Subdepartment of Quaternary Research, Cambridge {Received i January 1959) (With 4 figures in the text) SUMMARY A small peat bog at Elstead, Surrey, has been investigated stratigraphically, by pollen analysis and by identification of macroscopic plant remains. The organic infillmg was largely completed in zones V, V and V of the Postglacial period. At the close of zone and in zone V both pollen and macroscopic remains testify to a varied and open vegetation containing many typical Lateglacial plants. Zone was dominated by birch and zones V, V and V by pine. The subzones a, b and c of zone V are recognizable and the general picture of forest history conforms to that of other sites in the south of England, permitting a date to be placed upon the main stages of infilling of the lakebasin, notably a phase of deposition of mineral material in subzone Vic, and a possible hiatus immediately afterwards. NTRODUCTON ln April 1940 Dr. H. Godwin and Professor A. R. Clapham visited a small bog 1.2 miles (1.9 km) south of Elstead, near Godalming, Surrey. They put down a hne of three borings and from one of these samples for pollen analysis were taken. Although these samples were widely spaced their analysis revealed beyond question the presence of stages of forest history very characteristic of the English pollen zones from V to V. Moreover, from the coarse detritus sieved off in preparation of the pollen samples, Miss J. Allison recovered a considerable number of plant macrofossils: she identified others from the lowermost 20 cm of the two remaining boreholes. The pollen diagram was not published, but some of the pollenanalytic results were made use of in the diagnosis of the pollenzone sequence for England and Wales (Godwin, 1940) and several of the plant identifications were later recorded for their appropriate zones (Godwin, 1956). When Dr. S. C. Seagrief came to work in Cambridge in 1950 he undertook reexamination of the site, as a result of which he prepared the pollen diagrams now reproduced (which amphfy but do not contradict the one made earlier), and the much more extensive hst of macroscopic plant remains presented in Table i. * Now at the Department of Botany, Rhodes University, Grahamstown, South Africa. 84

2 Pollen diagrams from southern England 85 STE The site of the bog is a short distance north of a small farm road running between Woolford's Copse and Woolford's arm. The bog is approximately 30 m wide and 100 m in length, with the long axis from north to south (ig. i). t occupies a small hollow in the nearly level surface of the surrounding terrain which is an area of the olkstone Beds of the Lower Greensand. The origin of the hollow is not known for there is neither any obvious sign of an entry or exit of a stream or drainage channel which might have caused its formation by erosion, nor any likelihood of the hollow being an old kettlehole, as this part of England is well outside the maximum extension of the icesheets. The present cover of the bog is apparently still building in many places, with a vegetation dominated by Molinia caerulea, but with abundant Juncus sylvaticus and Sphagna ig.. Sketch map to show the locality of the investigated site at Elstead, Surrey. STRATGRAPHY The general character of the deposits filling the basin is conveyed by ig. 2, which illustrates both the three borings taken in 1940 and the four subsequently made in The infilling is largely organic mud (nekron mud) containing a greater or less amount of detritus, and usually very wet and unconsolidated. At some levels these muds contain remains oi Phragmites, at others there are remains of sedges, Polytrichum stems, or wood of birch and pine. All these appear to be indicative of phases of invasion of the lake by

3 86 S. C. SEAGRE AND H. GODWN reed swamp or sedge mat, the latter possibly bearing trees. Sphagnum peat such as might be formed by the present vegetation of the bog is thin and superficial, clearly relating to extremely recent conditions. Rather above halfway up the basin profile both sets of borings show the presence of layers of clay, silt or sand, and a similar but more recent and more localized occurrence is recorded just below the surface of bores Nos. io and 14. We shall revert to consideration of these stratigraphic phenomena after discussion of the results of pollen analyses and identifications of macroscopic plant material. w bore number Sphagnum peat ig, 2, Schematic representation of sections obtained by boring across the bog at Elstead, Surrey,, \ g side the column for bore No, 14 has been placed the pouenzonation determined from analyses shown in ig, 3 POLLEN DAGRAMS (igs, 3 and 4) Before commenting upon the zoning of the diagrams it should be pointed out that since wood remains, chiefly of Betula and Pinus, have been found at many levels in the borings, we may certainly suppose both genera to be overrepresented. n particular the very irregular nature of the Betula curve can be attributed to this, and possibly also the great preponderance of Almis in the top part of the diagram. Zone ; cm Betula is dominant but Pinus is in substantial amount and the presence of pine needles shows local presence ofthe tree, Salix and Corvlus are present in low frequencies. The ratio of herbaceous plants to trees is high, though rapidly falling, and this corresponds with a typically varied assemblage of Lateglacial indicator genera such as Artemisia, Campanula, Centaurea, Helianthenium, Plantago, Polemonium, Scabiosa, Thalictrum and Valeriana. Rich herbaceous vegetation at this early time is also indicated by presence of pollen of families such as Caryophyllaceae, Chenopodiaceae, Compositae, Cruciferae, Labiatae, Leguminosae, Ranunculaceae and Umbelliferae.

4 Pollen diagrams from southern England 87 n zone there are also considerable frequencies of Gramineae, Cyperaceae and of aquatic plants such as Menyanthes, Myriophyllum alterniflorum, Nymphaca, Potamogeton, Sparganium/Typha angustifolia and f. latifolia. The very high ericoid pollen values may be associated with the abundant macroscopic remains of Empetrum at this level. Zone V; cm Pinus values mostly exceed those of Betula. Slight amounts of Quercus, Tilia, Alnus, Salix and Corylus occur, but whilst Salix is probably autochthonous, it is impossible to say whether the more thermophilous genera may not have been introduced by contamination from above in sampling these very wet muds. Pollen of herbaceous genera and families persists in diminishing amount, no doubt as woodland cover became closed. The presence of substantial frequencies of Sphagnum spores in this and succeeding zones reinforces the Empetrum evidence from zone that the soils were already acidic. Zone V; cm Zone V is short and indeed very doubtfully separate from the underlying zone. Zone V; cm The beginning of the zone is indicated by the initiation of continuous curves for Ulmus and Quercus and by the swiftly rising Corylus curve. Pinus remains dominant throughout the zone: most of the plant indicators of open dry soil conditions have disappeared, and the herbaceous pollen seems attributable to local vegetation growing over the basin. A tentative division of the zone into subzones a, b and c has been made. Zone V, etc.; 8510 cm The transition from zone V to zone V is unmistakably indicated at 85 cm, where not only does the Alnus curve rise very steeply, but the continuous Tilia curve begins. t is to be noted that Ulmus values are very low above 85 cm, and this emphasizes the query raised by the presence of sand and clay layers in the upper layers of the bog, whether there might not be a substantial discontinuity at about 85 cm. Certainly this uppermost 85 cm cannot well represent 7000 years of continuous peat accumulation and one must remark the absence of pollen of agus and Carpinus. t seems probable that the final rise of Pinus pollen may be attributed to the recent period of conifer planting, and stray grains of Picea and Abies in the top two or three samples support this view: the rise of ericoid pollen may represent a corresponding vegetational change with podsolization, as may the thin and recent cover of the bog by Sphagnum. MACROSCOPC REMANS The finds of fruits, seeds and other kinds of remains from Elstead are given in Table i. The basal few centimetres of nekron mud were particularly rich in plant remains. Of particular interest are the fruits and leaves of Empetrum nigrum. Jessen (1949) has shown that this species formed extensive heaths in the northwest of reland during Lateglacial times. At Elstead Empetrum was obviously a common plant in zone, and it may well be that there were Empetrum heaths in the locality at this time which persisted until the opening of zone V and subsequent forest domination.

5 S. C. SEAGRE AND H. GODWN

6 Pollen diagrams from southern England 89 SPHAGNUM PTEPDUM POLYPODUM OSMUNDA L1CALE5 VALERANA ULMAPA = THALiCTWM SCABiOSA RUME POLEMONUM PLANTAGO HELANTHEMUM CENTAUREA CAMPANULA ARTEMSA UMBELLEERAE RO5ACEAE RANUNCULACEAE EPCALES CRUCEERAE h COMPOS itae CHENOPODACEAE CARYOPHYLLACEAE CYPERACEAE GRAH[^EAE TYPHA LAT. SPARGANUM/TYWA ANC POTAMOGETON NYMPHAEA MYROPHYLLUM ALT, MENYANTHES

7 90 S. C. SEAGRE AND H. GODWN These records confirm and much extend earher identifications made by Miss J. Allison whilst the earlier investigations were in progress. However, the following records by Miss Allison from zone V layers are additional to those in the table: Nymphaea alba, Sparganium minimum, ; Viola sp., S; Cristatella sp., statoblasts. Of particular interest are the identifications of Betula nana, B. nana /pubescens and Linaria vulgaris from the zone layers: these are species already associated with the Lateglacial period elsewhere (Godwin, 1956). t is quite clearly proven that at the very opening of the Postglacial period pine was present, as has already been shown at other southern English sites (Seagrief, 1959). Betula sp. B. nana B, nana ; pubescens B. pubescens B, verrucosa Calluna vulgaris Carex sp. C. cf. panicea C, rostrata Cirsium palustre Empetrum nigruni Erica tetralix Eupatorium cannabinum ilipendula ulmaria Gramineae Linaria \ailgaris Lycopus europaeus Menvanthes trifoliata Pinus sylvestris Polygonum persicaria Potamogeton natans Potentilla sp. Ranunculus Batrachium Scirpus sp. Sphagnum sp. Table i. Elstead macroscopic remains W, Sc, Sc, Sc L N N N, L L A S S s W, L st A A N L 6 26 O V S Zone V Via V S A, achene;, fruit; st, fruitstone; L, leaf; N, nutlet; S, seed; Sc, scale; W, wood. The sign x merely indicates the presence of the species. The abundant remains of Empetrum nigrum, together with the leaves of Erica tetralix and the fairly high frequencies of Ericales pollen indicate that suitable soils were available at this time for the establishment of 'heath' vegetation in the locality. None the less it must be recalled that the pollen indicates the local presence in the same earliest layers of more calcicolous plants such as Helianthemum sp. and Polemonium caeruleum. Abundant achenes of batrachian Ranunculi and fruitstones of Potamogeton confirm the presence of open water in the earliest phase of deposition, in agreement with the indications of the pollen. During subzones Via and V6 there are very abundant fruits of sedges, just as the herbaceous pollen curve for Cyperaceae registers high values: abundant remains of the birches correspond with irregular and high values of birch pollen, and identifications of fruits of Lvcopus europaeus, ilipendula ulmaria and Eupatorium cannabinum also occur here. The abundant wood seen in borings 3, 7, 9 and 23 at the corresponding level strengthen the view that during subzones Via and y\b the basin was largely overgrown by sedge mat carrying birch trees and perhaps willow, and in some places by reed swamp of Phragmites. t would appear reasonable to associate this vegetation change with a tendency to climatic dryness. 5

8 Pollen diagrams from southern England 91 The considerable deposition of sand, silt and clay, to which reference has already been made, is now seen to be associated with the latest part of zone V, and one is tempted to associate this with the possible hiatus in deposition at the zone V/V boundary. Likewise, this effect recalls that at other British sites (Hockham Mere, Norfolk; Elixton, Yorks. (Godwin 1956)) low lakelevels characterized the closing stages of the Boreal period. t is, however, uncertain whether these mineral layers should be attributed to falling water level and opening of ground cover on the mineral soil, or whether sharply increased precipitation would explain them. The very rapid accumulation of organic material in the Preboreal and Boreal periods, with a corresponding cessation afterwards, strongly recalls the same circumstances already noted in other southern Enghsh sites (Seagrief, 1959, i960). ACKNOWLEDGMENTS The authors wish to extend warm thanks for assistance received in the fiejd and laboratory, particularly to Professor A. R. Clapham, Miss J. Allison, Mrs. H. M. P. Whitmore and Miss R. Andrew. During his work on this project S. C. Seagrief held a Beit Memorial Railway Studentship and he wishes to acknowledge his indebtedness for this to the Beit Trustees. REERENCES GODWN, H. (1940). Pollen analysis and forest history of England and Wales. Neiv PhytoL, 39, 370. GODWN, H. (1956). The History of the British lora. Cambridge. SEAGRE, S. C. (1959). Pollen diagrams from southern England: Wareham, Dorset, and Nursling, Hants. New PhytoL, 58, 316. SEAGRE, S. C. (i960). Pollen diagrams from southern England: Cranes Moor, Hants. Nezc PhytoL,

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