POLLEN DIAGRAMS FROM SOUTHERN ENGLAND: GRANES MOOR, HAMPSHIRE

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1 POLLEN DIAGRAMS FROM SOUTHERN ENGLAND: GRANES MOOR, HAMPSHIRE BY S. C. SEAGRIEF University Sub-department of Quaternary Research, Cambridge* {Received i December 19S8) (With 7 figures in the text) SUMMARY Pollen analyses have been made from three parts of a New Forest valley bog system, Hampshire, England. The wide valleys excavated in the preceding Full-glacial or Lateglacial time were shown to be filled by organic deposits accumulated rapidly during the Pre-boreal and Boreal periods, Pinus is shown to have been strongly dominant throughout this time, and the sub-zones a, b and c of pollen zone VI are clearly and characteristically displayed. The beech [Fagus sylvatica) is shown to have been present already in the Boreal period. These results conform with those already reported from southern England, Although at the site there is evidence of the persistence of open habitat plants of the Late-glacial into the early Post-glacial, thereafter the record is one of closed woodland. Deposits later than early zone VII (Atlantic) are not present. INTRODUCTION Cranes Moor, i mile west of Burley in the New Forest, is a large and complex area of bog and heath, much of it underlain by Barton Sands, Burley Ridge to the east of Cranes Moor is composed of Headon Beds, capped in places by plateau gravels. From the conspicuous watershed of Burley Ridge comes much of the drainage water to Cranes Moor. To the south and west there is less high ground, but the springs and soakways of this part also drain into the central basin of Cranes Moor. The outlet of the basin is in the north-west corner at Kingston Common (Fig. i). Preliminary investigations revealed that the depressions on the eastern side of Cranes Moor contained the deepest peat deposits, and also that changes in the surface vegetation at different parts of the bog-complex were accompanied by changes in the underlying peat types. Thus, at the three sites which were examined in detail. Flush Bog was composed of muds and peats of a fen type. Little Bog had both fen and Sphagnum peats, while at Sphagnum Bog, the largest of the three bogs, the peat was almost entirely composed of Sphagnum remains, except under the Schoenus, where rootlet peats had developed. From observations of the topography it is clear that Flush Bog receives the major portion ofthe drainage water from Burley Ridge, while Little Bog and the northern part {Schoenetum) of Sphagnum Bog receive a lesser supply. The remainder of Sphagnum Bog is protected from the influence of this drainage water by a shallow sandy ridge separating it from the hillside. SPHAGNUM BOG From cm, the creamy-white Sphagnum mud is exactly like a face-cream in texture. A boring in the deepest part ofthe bog showed that similar white muds extended * Now at the Department of Botany, Rhodes University, Grahamstown, South Africa, 73

2 74 S. C. SEAGRIEF from 350 cm to 500 cm. At these depths and with the soft mud offering veiy little resistance to the borer it is extremely difficult to take pollen samples. According to the results of the present investigation Sphagnum Bog began accumulating in zone V, and it seems highly probable that if pollen samples were to be taken to a depth of 500 cm in the deepest part, the history of the bog would be extended to an earlier time. Field records ofthe stratigraphy from site i, Sphagnum Bog, are as follows: cm Sphagnum peat of variable degree of humification with fruits of Cladium mariscus at 150 and cm Soft caramel-coloured Sphagnum mud with occasional monocot. remains. Cladium between cm Rather coarser granular (not sandy) Sphagnum mud Creamy-white Sphagnum mud. 370 Sand..- MARCIN OF aoc -> WATCH FLOW TRANSECT PINE 100 2OO 3OO 4OOm Fig. I. Sketch map showing Cranes Moor Bog. Pollen samples were taken at sites CY, I and C12. Drainage lines are indicated by arrows. Pollen-analytic results By virtue of the high values for Pimis and the rising values for Corylus the lowest part of the diagrams (Figs. 2 and 3) clearly falls into zone V of the Boreal period (Godwin, 1940). Although the ratio of tree pollen to non-tree pollen is very high, indicating closed forest conditions, there are occasional records of plants generally associated with open

3 Pollen diagrams from Cranes Moor 75 habitats, such as Ericales (including Empetrum), Chenopodiaceae, Conipositae, Cruciferae, Artetmsia and Plantago lanceolata. The records for the last-named species are of especial interest because it so much predates the usual outburst of this pollen with the onset of Neolithic forest clearance near the zone Vila/VI16 boundary. The opening of zone VI is indicated by marked increases in values of Ulmus and Quercus. Sub-zone Via is delimited from cm, where Ulmus values exceed those of Quercus. Pinus is dominant, while Corylus values are fluctuatingly high. Sub-zone Ylb begins at 220 cm where Quercus values exceed those of Ulmus, Pinus is fauing, Betula values rise slightly and Corylus maintains high values on the whole. The upper limit of sub-zone Ylb has been tentatively placed at 140 cm, where Tilia pollen and Almis pollen are recorded slightly more often than previously. The sharp increase of Alnus to maintained higher values at 95 cm delimits the end of sub-zone Vic and the opening of zone VII. Fagus pollen is recorded at the VIc/VII transition and again in zone VII. In zone VII Alnus is dominant, with Quercus, Ulmus, Betula and Pinus represented respectively in decreasing order of abundance. As there is no marked fall in the Ulmus curve to indicate the opening of the Sub-boreal, sub-zone Vllb (Godwin, 1940), it is assumed that towards the end of the Atlantic period active bog growth ceased on Sphagnum Bog. The proportion of tree to non-tree pollen is very high throughout the pollen sequence, indicating that forest cover was extensive. The virtual absence of wood remains in Sphagnum Bog suggests that the tree pollen curves reflect the regional pollen rain and that local influences have been slight. In spite of the fact that Sphagnum is the chief bog component, the spores of Sphagnum are never very abundant, although there is a slight tendency for them to be commoner where the Sphagnum peat shows signs of humiflcation. Hedera pollen is noted in small amounts from the beginning of Ylb onwards, and Lonicera pollen is recorded once from Ylc. The curves and records of presence of the various herbaceous families and genera show little variation. LITTLE BOG, C12 Since Little Bog and Sphagnum Bog form part of the same system of bog grow th, it is not unexpected that their pollen-analytic results should be closely similar, although differences in stratigraphy between the two sampling sites are indicated by slight shifts in emphasis of the curves for some of the non-tree pollen types. In a section based on borings across Little Bog (Fig. i) it was seen that there is a tendency for the predominantly monocotyledonous rootlet peat to contain more abundant Sphagnum remains above a level which varied from cm across the bog. The stratigraphy at the pollen site C12 is as follows: cm o- 20 Disturbed peat Rather muddy rootlet peat with abundant Sphagnum Light brown rootlet peat with abundant Sphagnum Dark brown soft rootlet peat; Phragmites between cni. Sphagnum much less evident Dark brown more fibrous rootlet peat; Phragmites at cm, and 218 cm; three nutlets of Carex sp. at 205 cm. Little Sphagnum Dark brown flrm rootlet peat Dark brown muddier rootlet peat; wood (cf. Betula) at 310 cm. Leaves of Sphagnum papillosum at 275 cm.

4 S. C. SEAGRIEF cm Dark rootlet mud, with Sphagnum leaves in pollen sample at 340 cm. Two nutlets of Carex sp. at 340 cm. 340 Sand. CRANES MOOR I 1952 SPHAGNUM BOG Vila Vic Fig. 2. Tree pollen diagram from Cranes Moor Sphagnum Bog. Block diagram on right shows tree pollen (blank) and non-tree pollen (horizontal shading) as percentages of total dry-land pollen. Pollen-analytic results The tree pollen curves from Little Bog (Fig. 4) are strikingly similar to those of Sphagnum Bog; again accumulation has been rapid throughout the Boreal period, and the sub-zones of zone VI are very distinct. Active accumulation apparently ceased some time during zone VII. The non-tree pollen curves (Fig. 5) contain little of interest, although one notes the presence of considerable frequencies of Hedera and Osmtinda in sub-zone Ylb, and of Plantago lanceolata and Artemisia early in zone VII. In the middle of zone VI there is also an unexplained development shown by strong maxima of Compositae, Pteridium and other fern spores at 175 cm shortly followed by a big rise in Gramineae: it may be significant that these phenomena correspond with a very pronounced minimum in the Ulmus pollen curve (Fig. 4). It is interesting to note further that, whereas Sphagnum remains in the stratigraphy only become prominent above 138 cm, the Sphagnum curve on the pollen diagram shows exactly the opposite situation, namely that Sphagnum spores are more abundant below 138 cm. Conway (1947) has reported a similar behaviour for Sphagnum from Ringinglow Bog, and suggests that it may be due to differing fruiting habits of the various species.

5 Pollen diagrams from Cranes Moor CRANES MOOR I 1952 SPHAGNUM BOG Fig. 3. Non-tree pollen diagram from Sphagnum Bog, Cranes Moor. FLUSH BOG Ofthe three bogs examined at Cranes Moor, Flush Bog has the major supply of drainage water from Burley Ridge. This is reflected in the stratigraphy by a sequence of monocotyledonous rootlet muds and peats in complete contrast to the neighbouring Sphagnum Bog, where Sphagnum peat predominates. The stratigraphy from the site (CY) where the pollen samples were taken follows. cm o- 25 Peat disturbed, but chiefly composed of Molinia and Myrica with Sphagnum and Eriophorum.

6 S. C. SEAGRIEF

7 Pollen diagrams from Cranes Moor 79 PTERIDIUM POLYPODIUM OSMUNDA SCABIOSA POLYCALA PLANTACO LANC CALIUM ARTEMISIA UMBELLIfERAE CRUCIFERAE COMPOSITAE CHENOPODIACEAE HEDERA I O SPARGANiUM/TYPHAA POTAMOCETON

8 8o S. C. SEAGRIEF

9 Pollen diagrams from Cranes Moor 8i SPHAGNUM PTERIDIUM POLYPODIUM OSMUNDA FILICALES RANUNCULACEAE ULMARIA THALICTRUM SCABIO5A FIANTACO HELIANTHEMUM EPILOBIUM CAMPANULACEAE UMBELLIFERAE RUBIACEAE CRUCIFERAE ERICALES COMPOSITAE CHENOPODIACEAE CARYOPHYLLACEAE CYPERACEAE CRAMINEAE TYPHA LATIFOLIA SPARCANIUM/TYPHA A MENYANTHES POTAMOCETOrj N.P.

10 82 S. C. SEAGRIEF cm Black muddy rootlet peat with Sphagnum leaves, Dark brown rootlet peat; Sphagnum leaves in pollen residues. Coarse granules at 100 cm, Greenish-brown rootlet peat with wood at 125, 135, 145 and 155 cm Brown rootlet mud with wood remains throughout. At 178 cm Phragmttes, and at 185 cm three nutlets of Carex sp, Grey rootlet mud with some wood remains. At 225 cm Betula pubescens bud scale. At 315 cm a Pinus leaf base, three Carex nutlets, one Menyanthes seed and a fruit-stone of Potamogeton. Menyanthes at 300 and 320 cm Greyish brown rootlet peat with wood, Carex, Potamogeton, and Menyanthes Slightly sandy mud. Fruit of Betula nana and bud scale of B. pubescens at 355 cm, Menyanthes, Carex and Potamogeton abundant Grey sandy mud. Fruit of Betula nana at 375 cm. Seeds of Menyanthes and fruit-stones of Potamogeton also recorded. 380 Sand. Pollen-analytic results In considering the pollen-analytic results from Flush Bog (Fig. 6) it must be borne in mind that at this site there has been little Sphagnum growth, and that wood is locally present throughout the deposit. The very high values for willow (Salix) pollen, and also the high initial values and subsequent very irregular values for birch (Betula) pollen, may be referred to the presence in situ of fenwoods, into which pine may also have entered. We can only suppose that it is the strong local pollen production of birch and pine that has caused the Corvhis pollen curve to be so much lower than those in the other Cranes Moor sites. Table i. Macroscopic remains from the lower layers of Flush Bog Betula sp. B, nana B, pubescens Carex sp. Menyanthes trifoliata Pinus sylvestris Potamogeton polygonifolius Ranunculus (Batrachium) Salix sp. w FF N S W, L Fst A W Zones A, achene; F, fruit; Fst, fruit-stone; L, leaf; N, nutlet; S, seed; W, wood; X, presence. It seems probable that the basal deposits were formed in zone IV, and it is to be noted that the non-tree pollen curves (Fig, 7) indicate some openness of vegetation, in that the high values for open pollen are accompanied by a considerable range of herbaceous types including Helianthemum, Plantago media, Thalictrum and Scabiosa. The presence of a Late-glacial relict, Betula nana, is attested by the fruit found at 375 cm. The opening of zone VI is recognizable at about 190 cm, when the substantial curves of Ulmus and Quercus commence. It is apparent that sub-zone Ylh begins at 70 cm when Quercus pollen has become substantially more abundant than that of Ulmus. Sub-zone Vie is absent, as is demonstrated by the complete absence of pollen of Alnus. IV X I X 89 7 X V

11 Pollen diagratns from Cranes Moor 83 CONCLUSION The three pollen series from Cranes Moor are substantially in agreement, and taken together they strongly support the vaudity of dividing zone VI into sub-zones «, b and c at least for southern England. The very high values for Pinus pollen in the earliest Post-glacial zones correspond with the results from Wareham and Dorset (Seagrief, 1959) and contrast strongly with the strong dominance of Betula in northern Britain. Although heath land is now widespread in the New Forest, the Cranes Moor pollen diagrams give no indication that they existed in the early Atlantic, despite evidence of this kind for Dorset (Seagrief, 1959). The occurrence at Wareham of Fagus pollen, consistently, though at low frequency, from the beginning of zone VII is supported by more sporadic but frequent early records of the pollen from Cranes Moor, and the early natural presence of the tree in southern England is thereby confirmed. At Wareham, Nursling and Cranes Moor alike the investigated deposits occur within valleys much deeper and very much wider than those of the streams now flowing there. The wide valleys may be regarded as having formed at a time when the rivers had greater volume than at present, and when sea level was lower than now. Similar valleys occur, of course, beneath the rivers of the East Anglian Fenland, and there the contained deposits extend as far back as the Late-glacial period. At Wareham, deposits of zone III were identified, at Cranes Moor of zone IV, and at Nursling of zone III, the latter in conformity with the results from the ancient Channel of the Ichen at Southampton (Godwin and Godwin, 1940). The rapidity of infilling of these wide valleys by organic deposits in Pre-boreal and Boreal time is very notable, and only in the later stages, if at all, can this have been due to worsening of drainage caused by the eustatic rise in ocean level. It seems more likely that these over-deepened valleys attracted the drainage water from the region of porous soils around them. The process of infilling was completed apparently by Late-boreal or early Atlantic time, and we have no evidence of the conditions of drainage and climate which brought it to an end. There is no indication, however, that it was associated with the pronounced climatic dryness in sub-zone Vlf that has been recognized in some parts of Britain (Godwin, 1956). It must of course be remembered that at all these sites recent human activities may have caused decay and removal of some of the upper peat layers. ACKNOWLEDGMENTS I have much pleasure in thanking the Beit Trustees for the 'Beit Railway Trust Fellowship for the Two Rhodesias', which I was privileged to hold from January 1950 to January I should also like to thank Dr. H. Godwin, Miss R. Andrew, Mrs. M. Seagrief and Dr. P. Newbould for their encouragement and help. REFERENCES CoNWAY, V. M. (1947). Ringinglovv Bog, near Sheffield, jf. EcoL, 34, 149. GODWIN, H. (1940a). Pollen analysis and forest history of England and Wales. Nem PhytoL, 39, 370. GODWIN, H. (1956). The Htstorv of the British Flora. Cambridge. GODWIN, H. & GODWIN, M. E. (1940). Submerged peat at Southampton. Nezv PhytoL, 39, 303. NEWBOULD, P. J. & GORHAM, E. (1956). Acidity and specific conductivity measurements in some plant communities ofthe New Forest Valley Bogs. J. EcoL, 44, 118. SEAGRIEF, S. C. (1059). Pollen diagrams from southern England; Wareham, Dorset, and Nurslmg, Hampshire. New PhytoL, 58, 316.

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