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A first fossil record for Scolytus scolytus (F.) (elm bark beetle): its occurrence in elm decline deposits from London and the implications for neolithic elm disease
Journalof
Archaeological
Science 1985,12,347-351
A First Fossil Record for Scolytus scolytus (F.) (Elm Bark Beetle): its Occurrence in Elm Decline Deposits From London and the Implications for Neolithic Elm Disease Maureen A. Girling” and James Greigb (Received
15 December
1984, accepted
18 January
1985)
A problem which has arisen in discussions of an elm-disease explanation for the Neolithic elm decline has been the lack of fossil records of Scolytus scolytus (F.) (elm bark beetle), which is the main carrier of the fungus which causesthe present epidemic of Dutch Elm Disease. Now, the discovery of wing casesof two individuals from elm decline deposits at Hampstead Heath, London, proves that the beetle was present in Britain during this episode. The deposits in which it occurs are described, and the various implications for elm diseasecausing, aiding or at least occurring during this stage of the early Neolithic are discussed. SCOL YTUS SCOL YTUS, BEETLES, CERATOCYSTIS, COLEOPTERA, ELM DECLINE, ELM DISEASE, FOREST CLEARANCE, HAMPSTEAD HEATH, BRITAIN, NEOLITHIC, POLLEN ANALYSIS, PLANT MACROFOSSIL.
Keywords:
Introduction The beetle Scolytus scolytus (F.) (= S. destructor 01.) is the main carrier of Ceratocystis ulmi, the fungus which causes Dutch Elm Disease. Although there are fossil records of other present British Scolytus species from late Pleistocene and Flandrian (postglacial) deposits, including archaeological contexts (e.g. Kelly & Osborne, 1965), S. scolytus has not been discovered before. Now, two individuals of S. scolytus have been found in prehistoric deposits at West Heath Spa, Hampstead Heath, London, l&15 cm below the level identified as the elm decline episode (Greig, in press). This find has important implications when considering the possible role of a disease such as Dutch Elm Disease during the Neolithic in Britain and probably the rest of Northwest Europe. The Mesolithic site of West Heath Spa (grid reference: TQ 260865) was excavated by D. Collins. It was discovered from the numerous finds of worked flints exposed by recreational pressures in the thin soils on the Bagshot Sands (Lorimer, 1976; Collins & Lorimer, in press) (Figure 1). Palaeoecological analyses of the waterlogged deposits of a spring-fed boggy area were carried out to provide environmental information for the site, with preliminary and final results indicating that the basal sediments were pre-elmdecline in age (Girling & Greig, 1977; Girling, in press; Greig, in press). A major problem of this investigation was that the numbers of insect and plant macrofossils were often very low. The sediments were mainly mineral, with sticky clays and compacted organic “Ancient Monuments Laboratory, sion for England, Fortress House,
Historic 23 Savile
bDepartment Birmingham
University
of Plant Biology, B 15 2TT, England.
Buildings and Monuments Row, London WlX 2HE, of
Birmingham,
P.O.
CommisEngland. Box
363,
347 0305Gl403/85/050347+05
%03.00/O
0 1985 Academic
Press Inc. (London)
Limited
348
M. A. GIRLING
AND J. GREIG
Figure 1. Location map for West Heath Spa. The sampled rises on West Heath, feeding a stream which flows westwards
site is a spring into a pond.
which
silts with pebbles. A very large sample of up to 5 kg was collected from each 5 cm depth of sediment, but despite this the plant and insect macrofossils were often rather scarce, although the pollen was abundant.
Pollen Analysis The pollen results (see summary diagram, Figure 2) have been presented as percentage values based on a pollen sum consisting of tree and shrub taxa (except Alnus, Salix and Corylus) together with dry-land herb taxa, but excluding mainly wet-land herbs such as Cyperaceae. This selection leaves out taxa which can produce large amounts of pollen, often in vegetation growing very near the site, the fluctuations of which could obscure the changes occurring in the regional vegetation. The lower part of the pollen diagram has very high tree pollen values averaging 96% in the samples from lo&120 cm depth, suggesting that there was a thick forest cover growing locally. When the pollen values are corrected so that they approximate more to the actual past tree cover (Andersen, 1970) the forest composition appears thus (uncorrected percentages in brackets): lime (Tdia) (27%) was dominant, providing about 75% of the forest cover, followed by oak (Quercus) (53%) with about 20% cover and elm (Urnus) (9%) with about 6%; other trees such as pine (Pinus) and birch (Betula) and shrubs such as ivy (Hedera) were also present. Alder (Alnus) was probably growing extensively in the wet area round the site and hazel (Corylus) may have formed a forest understory. Further signs that the immediate surroundings of the site were perhaps unrepresentative of the forest as a whole are in the seed results: only birch (Betula) was found. Other ancient lime forest sites have produced lime fruits (e.g. Kelly & Osborne, 1965) so perhaps the Hampstead bog was in a glade. Some disturbance of the forest is shown by the presence of traces of Plantago lanceolata (ribwort plantain), Artemisia (mugwort) and some cereal-type pollen. Such signs of pre-elm-decline farming are
FOSSIL
RECORD
FOR SCOL YTCJSSCOL YTUS WEST
HEATH
349
SPA
J-JII/gT/
0
IO
20
Percentage
30
40
dry-land
50
60
pollen
70 except
60
90 100 15 IO Coryhs
5
Species
0
5
IO
lndwiduals
15
IO
5
0
Speaes
Figure 2. A summary of the tree and herb pollen, and treebeetle results, from part of the West Heath Spa core.
5
IO
lndwduols
and dung-dependent
considered to represent early Neolithic agriculture (Groenman-van Waateringe, 1983; Edwards & Hirons, 1984). The upper part of the diagram, 95-70 cm, has significantly lower Ulmus pollen values, which fall from an average of 9% to 1%, a change which is used to define the elm decline here. Associated changes are a general fall in tree pollen and a rise in the representation from indicators of disturbed land such as plantain. Seeds are much more abundant and are mainly from wet-land herbs such as sedges. There are no radiocarbon dates from this profile because of the problems of fine rootlet penetration, but this horizon may well be contemporary with other dated elm-decline horizons from deposits in the British Isles, which range between about 3300 and 2900 years bp (Smith & Pilcher, 1973).
Insect Analysis The sequential changes which occur in the insect assemblages correspond well with the results of the pollen analysis (Figure 2). The pre-elm-decline forest stage is dominated by tree-dependent beetles which include the lime feeder Ernoporus caucasicus Lind. which is now regarded as an insect of primary forest. There are many decayed wood inhabitants, amongst them two species of beetle which no longer occur in Britain [Zsorhipis melusoides (Lap.) and Pycnomeris terebrans 01.1 and the whole group is typical of very mature forest. Scolytus scolytus occurs 15 cm below the elm-decline horizon, and at the elm decline itself dung beetles appear, mainly Aphodius species, which are present in most of the subsequent layers as well. There is a corresponding reduction in woodland beetles, although decayed wood species are recorded throughout. The increase of aquatic beetles at the elm-decline horizon shows that the site became wetter, perhaps as a result of tree removal.
350
M. A. GIRLING
AND
J. GREIG
Discussion A number of hypotheses have been proposed to explain the Neolithic elm decline, including climatic, ecological and anthropogenic factors. The latter includes both the destruction of trees to clear the land, and grazing and foliage lopping for livestock feed (Iversen, 1941; Troels-Smith, 1960). As the effects of the most recent outbreak of Dutch Elm Disease became apparent from the 1960s onwards in Northwest Europe (Rackham, 1980) the further hypothesis of disease is finding increasing, but not universal favour (e.g. Watts, 1961; Heybroek, 1963; ten Hove, 1968; Rackham, 1980; Huntley & Birks, 1983). The pathogen theory is supported by the view that there were not enough people and livestock in Neolithic times to cause the elm decline (Rackham, 1980; Rowley-Conwy, 1982). Furthermore, it may be noted that in North America a recent decline in chestnut caused by a pathogen has provided an analogy for a prehistoric decline of that tree (Davis, 198 1). The first records of the beetle which carries the present-day Dutch Elm Disease, close to the elm-decline horizon, draws attention to disease as a possible factor. Although Ceratocystis ulmi, the fungal pathogen responsible for the present epidemic, is not necessarily the agent involved, it is certainly a likely candidate. Dutch Elm Disease is thought to have spread from Asia to Europe early in this century and subsequently to Britain by 1927, but Rackham (1980) has suggested that 19th century and even perhaps Shakespearian references are to earlier outbreaks in Britain, and that Venetian plays of the 1500s could refer to the same disease. Ceratocystis is genetically unstable, and mutations may result in renewed attacks from different strains of the same disease. The high elm mortality in the present outbreak is probably a reflection of the trees’ low resistance to the particularly virulent Canadian strain (Gibbs & Brasier, 1973). In the light of the Neolithic record of S. scolytus from Hampstead Heath and our existing knowledge of archaeological and palaeoecological information on the late Mesolithic/early Neolithic periods, a number of possible factors can be put forward in discussing the elm decline. (1) Scolytus scolytus could have been absent from Britain until the Neolithic. However, the beetle flies strongly and disperses rapidly, so it should have been able to follow the elms as they colonized Northwest Europe and Britain in the early postglacial period. Despite its ease of dispersal, S. scolytus is typically an inhabitant of clearings, hedges and isolated copses or single trees and it would not have been favoured by primary dense forest once this was established. (2) Pathogens could have been absent until Neolithic or still more recent times. This could be difficult to confirm because the chance of finding and identifying diseased wood is remote since the affected sapwood rarely survives. Also, the dark staining of the rings when a tree survives an attack might be masked by the normal staining of waterlogged wood. (3) Neolithic farmers may have introduced or inadvertently encouraged the spread of the beetle, the pathogen, or both by using infected timber. (4) Frequent foliage stripping or pollarding for animal feed or timber would have caused the trees stress as they produced rapid new growth. This might have made them more susceptible to disease. (5) If dead elms and wood were left in place, these could have provided a good breeding ground for S. scolytus from which it could spread elm disease. Any combination of these factors could have taken place and a combination of human activities and disease seems a more likely possibility for the cause of the elm decline than previously advanced hypotheses. This note records the presence of a known beetle carrier of elm disease near the stratigraphic point of a Southern British elm decline. Scolytus scolytus records from the
FOSSIL
RECORD
early Neolithic period do not themselves do add some more evidence to the debate.
FOR SCOL YTUS SCOL YTUS identify
the cause of the elm decline,
351 but they
Acknowledgements This work was supported the Environment, now England.
by the Ancient of the Historic
Monuments Buildings
Laboratory of the Department and Monuments Commission
of for
References Andersen, S. Th. (1970). The relative pollen productivity and pollen representation of north European trees, and correction factors for tree pollen spectra. Danmarks geologiske Undersagelsr, Ser. II 96, l-99. Collins, D. & Lorimer, D., Eds (in press). Excavations at West Heath, Humpstead, to be published by the Museum of London. Davis, M. B. (198 1). Outbreaks of forest pathogens in Quaternary history. In Proceedings ofthe 4th International Conference on Palynology, Lucknow, India (19767) 3,216227. Edwards, K. J. & Hirons, K. R. (1984). Cereal pollen grains in pre-elm decline deposits: Implications for the earliest agriculture in Britain and Ireland. Journal of Archaeological Science 11,71b80. Gibbs, J. N. & Brasier, C. M. (1973). Correlation between cultural characters and pathogenicity in Ceratocystis ulmi from Britain, Europe and America. Nature 241,38 l-383. Girling, M. A. (in press). Mesolithic and later landscapes interpreted from the insect assemblages of West Heath Spa, Hampstead. In (D. Collins & D. Lorimer, Eds) Excavations at West Heath, Hampstead, to be published by the Museum of London. Girling, M. A. & Greig, J. R. A. (1977). Palaeoecological investigations at a site at Hampstead Heath, London. Nature 268,45-47. Greig, J. R. A. (in press). From lime forest to heathland-five thousand years of change at West Heath Spa. In (D. Collins & D. Lorimer, Eds) Excavations at West Heath, Humpstead, to be published by the Museum of London. Groenman-van Waateringe, W. (1983). The early agricultural utilisation of the Irish landscape: the last word on the elm decline? In (T. Reeves-Smith & F. Hamond, Eds) Landscape Archaeology in Ireland. British Archaeological Reports S116, 2 17-232. Heybroek, H. M. (1963). Diseases and lopping for fodder as possible causes of a prehistoric decline of Ulmus. Acta Botanica Neerlandica 12, I-I 1. Hove, H. A. ten (1968). The Ulmus fall at the transition Atlanticum-Subboreal in pollen diagrams. Palaeogeography, Palaeoclimatology, Palaeoecology 5,359-369. Huntley, B. & Birks, H. J. B. (1983). An Atlas of Past and Present Pollen Mapsfor Europe: O-13,000 years age. Cambridge: Cambridge University Press. Iversen, J. (1941). Landnam i Danmarks Stenalder. Danmarksgeologiske Undersggelse, Ser. II, 66, 1-68 (1964 reprint). Kelly, M. & Osborne, P. J. (1965). Two floras and faunas from the alluvium at Shustoke, Warwickshire. Proceedings of the Linnean Society of London 176,37-65. Lorimer, D. H. (1976). A Mesolithic site on West Heath, Hampstead - a preliminary report. London Archaeologist 2,407409. Rackham, 0. (1980). Ancient woodland: its history, vegetation and uses in England. London: Arnold. Rowley-Conwy, P. (1982). Forest grazing and clearance in temperate Europe with special reference to Denmark: an archaeological view. In (M. Bell & S. Limbrey, Eds) Archaeological Aspects of Woodland Ecology. British Archaeological Reports S146, 199-215. Smith, A. G. & Pilcher, J. R. (1973). Radiocarbon dates and vegetational history of the British Isles. New Phytologist 72,903-914. Troels-Smith, J. (1960). Ivy, mistletoe and elm. Climate indicators - fodder plants. Danmarks geologiske Undersegelse, Ser. IV, 4, l-32. Watts, W. A. (1961). Post-Atlantic forests in Ireland. Proceedings of the Linnean Society of London 172.33-38.
Archaeological
Science 1985,12,347-351
A First Fossil Record for Scolytus scolytus (F.) (Elm Bark Beetle): its Occurrence in Elm Decline Deposits From London and the Implications for Neolithic Elm Disease Maureen A. Girling” and James Greigb (Received
15 December
1984, accepted
18 January
1985)
A problem which has arisen in discussions of an elm-disease explanation for the Neolithic elm decline has been the lack of fossil records of Scolytus scolytus (F.) (elm bark beetle), which is the main carrier of the fungus which causesthe present epidemic of Dutch Elm Disease. Now, the discovery of wing casesof two individuals from elm decline deposits at Hampstead Heath, London, proves that the beetle was present in Britain during this episode. The deposits in which it occurs are described, and the various implications for elm diseasecausing, aiding or at least occurring during this stage of the early Neolithic are discussed. SCOL YTUS SCOL YTUS, BEETLES, CERATOCYSTIS, COLEOPTERA, ELM DECLINE, ELM DISEASE, FOREST CLEARANCE, HAMPSTEAD HEATH, BRITAIN, NEOLITHIC, POLLEN ANALYSIS, PLANT MACROFOSSIL.
Keywords:
Introduction The beetle Scolytus scolytus (F.) (= S. destructor 01.) is the main carrier of Ceratocystis ulmi, the fungus which causes Dutch Elm Disease. Although there are fossil records of other present British Scolytus species from late Pleistocene and Flandrian (postglacial) deposits, including archaeological contexts (e.g. Kelly & Osborne, 1965), S. scolytus has not been discovered before. Now, two individuals of S. scolytus have been found in prehistoric deposits at West Heath Spa, Hampstead Heath, London, l&15 cm below the level identified as the elm decline episode (Greig, in press). This find has important implications when considering the possible role of a disease such as Dutch Elm Disease during the Neolithic in Britain and probably the rest of Northwest Europe. The Mesolithic site of West Heath Spa (grid reference: TQ 260865) was excavated by D. Collins. It was discovered from the numerous finds of worked flints exposed by recreational pressures in the thin soils on the Bagshot Sands (Lorimer, 1976; Collins & Lorimer, in press) (Figure 1). Palaeoecological analyses of the waterlogged deposits of a spring-fed boggy area were carried out to provide environmental information for the site, with preliminary and final results indicating that the basal sediments were pre-elmdecline in age (Girling & Greig, 1977; Girling, in press; Greig, in press). A major problem of this investigation was that the numbers of insect and plant macrofossils were often very low. The sediments were mainly mineral, with sticky clays and compacted organic “Ancient Monuments Laboratory, sion for England, Fortress House,
Historic 23 Savile
bDepartment Birmingham
University
of Plant Biology, B 15 2TT, England.
Buildings and Monuments Row, London WlX 2HE, of
Birmingham,
P.O.
CommisEngland. Box
363,
347 0305Gl403/85/050347+05
%03.00/O
0 1985 Academic
Press Inc. (London)
Limited
348
M. A. GIRLING
AND J. GREIG
Figure 1. Location map for West Heath Spa. The sampled rises on West Heath, feeding a stream which flows westwards
site is a spring into a pond.
which
silts with pebbles. A very large sample of up to 5 kg was collected from each 5 cm depth of sediment, but despite this the plant and insect macrofossils were often rather scarce, although the pollen was abundant.
Pollen Analysis The pollen results (see summary diagram, Figure 2) have been presented as percentage values based on a pollen sum consisting of tree and shrub taxa (except Alnus, Salix and Corylus) together with dry-land herb taxa, but excluding mainly wet-land herbs such as Cyperaceae. This selection leaves out taxa which can produce large amounts of pollen, often in vegetation growing very near the site, the fluctuations of which could obscure the changes occurring in the regional vegetation. The lower part of the pollen diagram has very high tree pollen values averaging 96% in the samples from lo&120 cm depth, suggesting that there was a thick forest cover growing locally. When the pollen values are corrected so that they approximate more to the actual past tree cover (Andersen, 1970) the forest composition appears thus (uncorrected percentages in brackets): lime (Tdia) (27%) was dominant, providing about 75% of the forest cover, followed by oak (Quercus) (53%) with about 20% cover and elm (Urnus) (9%) with about 6%; other trees such as pine (Pinus) and birch (Betula) and shrubs such as ivy (Hedera) were also present. Alder (Alnus) was probably growing extensively in the wet area round the site and hazel (Corylus) may have formed a forest understory. Further signs that the immediate surroundings of the site were perhaps unrepresentative of the forest as a whole are in the seed results: only birch (Betula) was found. Other ancient lime forest sites have produced lime fruits (e.g. Kelly & Osborne, 1965) so perhaps the Hampstead bog was in a glade. Some disturbance of the forest is shown by the presence of traces of Plantago lanceolata (ribwort plantain), Artemisia (mugwort) and some cereal-type pollen. Such signs of pre-elm-decline farming are
FOSSIL
RECORD
FOR SCOL YTCJSSCOL YTUS WEST
HEATH
349
SPA
J-JII/gT/
0
IO
20
Percentage
30
40
dry-land
50
60
pollen
70 except
60
90 100 15 IO Coryhs
5
Species
0
5
IO
lndwiduals
15
IO
5
0
Speaes
Figure 2. A summary of the tree and herb pollen, and treebeetle results, from part of the West Heath Spa core.
5
IO
lndwduols
and dung-dependent
considered to represent early Neolithic agriculture (Groenman-van Waateringe, 1983; Edwards & Hirons, 1984). The upper part of the diagram, 95-70 cm, has significantly lower Ulmus pollen values, which fall from an average of 9% to 1%, a change which is used to define the elm decline here. Associated changes are a general fall in tree pollen and a rise in the representation from indicators of disturbed land such as plantain. Seeds are much more abundant and are mainly from wet-land herbs such as sedges. There are no radiocarbon dates from this profile because of the problems of fine rootlet penetration, but this horizon may well be contemporary with other dated elm-decline horizons from deposits in the British Isles, which range between about 3300 and 2900 years bp (Smith & Pilcher, 1973).
Insect Analysis The sequential changes which occur in the insect assemblages correspond well with the results of the pollen analysis (Figure 2). The pre-elm-decline forest stage is dominated by tree-dependent beetles which include the lime feeder Ernoporus caucasicus Lind. which is now regarded as an insect of primary forest. There are many decayed wood inhabitants, amongst them two species of beetle which no longer occur in Britain [Zsorhipis melusoides (Lap.) and Pycnomeris terebrans 01.1 and the whole group is typical of very mature forest. Scolytus scolytus occurs 15 cm below the elm-decline horizon, and at the elm decline itself dung beetles appear, mainly Aphodius species, which are present in most of the subsequent layers as well. There is a corresponding reduction in woodland beetles, although decayed wood species are recorded throughout. The increase of aquatic beetles at the elm-decline horizon shows that the site became wetter, perhaps as a result of tree removal.
350
M. A. GIRLING
AND
J. GREIG
Discussion A number of hypotheses have been proposed to explain the Neolithic elm decline, including climatic, ecological and anthropogenic factors. The latter includes both the destruction of trees to clear the land, and grazing and foliage lopping for livestock feed (Iversen, 1941; Troels-Smith, 1960). As the effects of the most recent outbreak of Dutch Elm Disease became apparent from the 1960s onwards in Northwest Europe (Rackham, 1980) the further hypothesis of disease is finding increasing, but not universal favour (e.g. Watts, 1961; Heybroek, 1963; ten Hove, 1968; Rackham, 1980; Huntley & Birks, 1983). The pathogen theory is supported by the view that there were not enough people and livestock in Neolithic times to cause the elm decline (Rackham, 1980; Rowley-Conwy, 1982). Furthermore, it may be noted that in North America a recent decline in chestnut caused by a pathogen has provided an analogy for a prehistoric decline of that tree (Davis, 198 1). The first records of the beetle which carries the present-day Dutch Elm Disease, close to the elm-decline horizon, draws attention to disease as a possible factor. Although Ceratocystis ulmi, the fungal pathogen responsible for the present epidemic, is not necessarily the agent involved, it is certainly a likely candidate. Dutch Elm Disease is thought to have spread from Asia to Europe early in this century and subsequently to Britain by 1927, but Rackham (1980) has suggested that 19th century and even perhaps Shakespearian references are to earlier outbreaks in Britain, and that Venetian plays of the 1500s could refer to the same disease. Ceratocystis is genetically unstable, and mutations may result in renewed attacks from different strains of the same disease. The high elm mortality in the present outbreak is probably a reflection of the trees’ low resistance to the particularly virulent Canadian strain (Gibbs & Brasier, 1973). In the light of the Neolithic record of S. scolytus from Hampstead Heath and our existing knowledge of archaeological and palaeoecological information on the late Mesolithic/early Neolithic periods, a number of possible factors can be put forward in discussing the elm decline. (1) Scolytus scolytus could have been absent from Britain until the Neolithic. However, the beetle flies strongly and disperses rapidly, so it should have been able to follow the elms as they colonized Northwest Europe and Britain in the early postglacial period. Despite its ease of dispersal, S. scolytus is typically an inhabitant of clearings, hedges and isolated copses or single trees and it would not have been favoured by primary dense forest once this was established. (2) Pathogens could have been absent until Neolithic or still more recent times. This could be difficult to confirm because the chance of finding and identifying diseased wood is remote since the affected sapwood rarely survives. Also, the dark staining of the rings when a tree survives an attack might be masked by the normal staining of waterlogged wood. (3) Neolithic farmers may have introduced or inadvertently encouraged the spread of the beetle, the pathogen, or both by using infected timber. (4) Frequent foliage stripping or pollarding for animal feed or timber would have caused the trees stress as they produced rapid new growth. This might have made them more susceptible to disease. (5) If dead elms and wood were left in place, these could have provided a good breeding ground for S. scolytus from which it could spread elm disease. Any combination of these factors could have taken place and a combination of human activities and disease seems a more likely possibility for the cause of the elm decline than previously advanced hypotheses. This note records the presence of a known beetle carrier of elm disease near the stratigraphic point of a Southern British elm decline. Scolytus scolytus records from the
FOSSIL
RECORD
early Neolithic period do not themselves do add some more evidence to the debate.
FOR SCOL YTUS SCOL YTUS identify
the cause of the elm decline,
351 but they
Acknowledgements This work was supported the Environment, now England.
by the Ancient of the Historic
Monuments Buildings
Laboratory of the Department and Monuments Commission
of for
References Andersen, S. Th. (1970). The relative pollen productivity and pollen representation of north European trees, and correction factors for tree pollen spectra. Danmarks geologiske Undersagelsr, Ser. II 96, l-99. Collins, D. & Lorimer, D., Eds (in press). Excavations at West Heath, Humpstead, to be published by the Museum of London. Davis, M. B. (198 1). Outbreaks of forest pathogens in Quaternary history. In Proceedings ofthe 4th International Conference on Palynology, Lucknow, India (19767) 3,216227. Edwards, K. J. & Hirons, K. R. (1984). Cereal pollen grains in pre-elm decline deposits: Implications for the earliest agriculture in Britain and Ireland. Journal of Archaeological Science 11,71b80. Gibbs, J. N. & Brasier, C. M. (1973). Correlation between cultural characters and pathogenicity in Ceratocystis ulmi from Britain, Europe and America. Nature 241,38 l-383. Girling, M. A. (in press). Mesolithic and later landscapes interpreted from the insect assemblages of West Heath Spa, Hampstead. In (D. Collins & D. Lorimer, Eds) Excavations at West Heath, Hampstead, to be published by the Museum of London. Girling, M. A. & Greig, J. R. A. (1977). Palaeoecological investigations at a site at Hampstead Heath, London. Nature 268,45-47. Greig, J. R. A. (in press). From lime forest to heathland-five thousand years of change at West Heath Spa. In (D. Collins & D. Lorimer, Eds) Excavations at West Heath, Humpstead, to be published by the Museum of London. Groenman-van Waateringe, W. (1983). The early agricultural utilisation of the Irish landscape: the last word on the elm decline? In (T. Reeves-Smith & F. Hamond, Eds) Landscape Archaeology in Ireland. British Archaeological Reports S116, 2 17-232. Heybroek, H. M. (1963). Diseases and lopping for fodder as possible causes of a prehistoric decline of Ulmus. Acta Botanica Neerlandica 12, I-I 1. Hove, H. A. ten (1968). The Ulmus fall at the transition Atlanticum-Subboreal in pollen diagrams. Palaeogeography, Palaeoclimatology, Palaeoecology 5,359-369. Huntley, B. & Birks, H. J. B. (1983). An Atlas of Past and Present Pollen Mapsfor Europe: O-13,000 years age. Cambridge: Cambridge University Press. Iversen, J. (1941). Landnam i Danmarks Stenalder. Danmarksgeologiske Undersggelse, Ser. II, 66, 1-68 (1964 reprint). Kelly, M. & Osborne, P. J. (1965). Two floras and faunas from the alluvium at Shustoke, Warwickshire. Proceedings of the Linnean Society of London 176,37-65. Lorimer, D. H. (1976). A Mesolithic site on West Heath, Hampstead - a preliminary report. London Archaeologist 2,407409. Rackham, 0. (1980). Ancient woodland: its history, vegetation and uses in England. London: Arnold. Rowley-Conwy, P. (1982). Forest grazing and clearance in temperate Europe with special reference to Denmark: an archaeological view. In (M. Bell & S. Limbrey, Eds) Archaeological Aspects of Woodland Ecology. British Archaeological Reports S146, 199-215. Smith, A. G. & Pilcher, J. R. (1973). Radiocarbon dates and vegetational history of the British Isles. New Phytologist 72,903-914. Troels-Smith, J. (1960). Ivy, mistletoe and elm. Climate indicators - fodder plants. Danmarks geologiske Undersegelse, Ser. IV, 4, l-32. Watts, W. A. (1961). Post-Atlantic forests in Ireland. Proceedings of the Linnean Society of London 172.33-38.