Vegetation history and climate of the last 15,000 years at Laghi di Monticchio, southern Italy

Quarernary Science Reviews, Vol. 15, pp. 113-132,1996. Copyright 0 1996 Elsevier Science Ltd. Printed in Great Britain. All rights reserved.

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VEGETATION HISTORY AND CLIMATE OF THE LAST 15,000 YEARS AT :LAGHI DI MONTICCHIO, SOUTHERN ITALY W.A. WATTS,* J.R.M. ALLEN,? B. HUNTLEYJ- and S.C. FRITZ+ tEnvironmenta1 *Department

*Department of Botany, Trinity College, Dublin 2, Ireland Re,yearch Centre, Department of Biological Sciences, University of Durham, South Road, Durham DHI 3LE, U.K. of Earth and Environmental Sciences, Lehigh University, Bethlehem, PA 18015, U.SA.

Abstract - In southern It;aly, vegetation contemporary with the end of the last glacial maximum, from 15,000 to 12,000 years ago, is shown by pollen-analysis to have been treeless and steppe-like in character. At 12,500 BP (years before present), Betula (birch) expanded into the steppe, quickly followed by Quercus (oak), Fugus (beech), Tilia (lime) and other tree genera of mesic forest. High percentages of lUia point to a rich mesic forest that was contemporary with the ‘Allerod’ interstadial of northern Europe. A major decline in mesic trees with an accompanying return of Beth and steppe genera dated to 10,500 years ago identifies a ‘Younger Dryns’ climatic reversal. Betula and steppe genera were replaced by forest of Quercus and other mesic trees, notably Ulmus (elm), as the Holocene began. In the later Holocene, ca. 4000 years ago, Abies (fir), Curpinus betulus (hombeam) and Taxus (yew) appeared. Abies and Tuxus became extinct locally about 2500 years ago, either because of climatic change, or perhaps because of the effects of early agriculture. The Fullglacial climate is thought to have been cold and summer-dry with mainly winter precipitation. The Lateglacial ‘Boiling-Allereld’ Interstadial was summer-wet and warm. The response-surface based climate reconstruction indi’zates an early Holocene climate with markedly colder winter conditions than today, about -5°C compared with 3.9-C today as a mean temperature for the coldest month. The annual temperature sum is reconstructed as somewhat higher than today, 3500 degree days as compared with a calculated value of 2900 for today. The later Holocene had a climate like today’s, Rainfall, and variation in iis seasonal distribution, has been a critical determinant of the vegetation cover. The fossil pollen record at Laghi Di Monticchio has been complemented by diatom and plant macrofossil studies which provide evidence of former lake environments as well as data on the upland forest. Lake levels remained high during the Full- and Lateglacial with encroachment of shore vegetation during th,e Holocene. The sediments also have an exceptionally rich record of tephra falls which are of importance in dating and core correlation. Twenty-one macroscopically visible tephras occur in sediments of the last 15,000 years. Copyright 0 1996 Elsevier Science Ltd

(Bottema,

QSR

1979; van Zeist and Bottema, 1991; van Zeist (1977) and Drescher-Schneider (1985) record a site at Canolo Nuovo at 900 m (in Calabria at the northern edge of the Aspromonte massif), which records a steppe-like ‘Older Dryas’ vegetation and a forested episode at 37,000 BP. Unfortunately, the sedimentary sequences at this site are short with large hiatuses. The Holocene of Italy is recorded at Valle di Castiglione (Alessio et al., 1986) and at Lago di Martignano (Kelly and Huntley, 1991). Both sites occur at low elevations, of 44 m and 200 m respectively, near Rome. They record the history of evergreen woodland and mixed deciduous woodland near the Tyrrhenian coast. In the northern Apennines, northeast of La Spezia, Lowe and Watson (1993) have studied a number of sites of which Prato Spilla D (1280 m), lies behind a moraine of local ice from the LGM. It shows evidence for a ‘Younger Dryas’ climatic episode and records the development of Holocene vegetation. These high-elevation sites differ from central and southern Italy in the constant presence of Pinus (pine) and of Abies.

INTRODUCTION

et al., 1975). Griiger

The flora history and inferred climatic history of southern Italy are poorly known. In recent years pollenanalytical investigations of maar lake sediments near Rome have yielded long records of vegetation history from a number of sites (Follieri et aE., 1993). The now drained lake at Valle di Castiglione (Follieri et al., 1988) contains a complete interglacial cycle from the Eemian to the present as well as a long pre-Eemian section with phases of temperate forest flora. Lagaccione contains a large part of the last glacial/interglacial cycle (Follieri et al., 1993) as does Lago di Vito (Francus et al., 1993). In contrast, little information is available from southern Italy. A preliminary study by Watts (1985) showed that Lago Grande di Monticchio (for site locations, see Fig. 1) contained a Holocene record as well as a large portion of the time of the Last Glacial Maximum (LGM). All the sites show a forested Holocene, while LGM floras show alternation of steppe-like vegetation with partly forested episodes. The steppe-like floras are similar to those recorded for the same period from Greece and Turkey 113

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FLEG

ISCI VE!

TYRRHEN

I S

E

A

A

IONIAN

OMONTE

1958

EVERGREEN

MONTANE

PANTELLERIA

WOODLAND

FOREST

AN

’

EA

FIG. 1. Location of sites referred to in the text. Map details and vegetation after Touring Club Italian0 (1958). Montane forest is Fagus-dominated.

Elevation, aspect, geographic location and climate can be shown to result in regional diversity in pollen records from Italy. The object of the expanded study of Monticchio was to provide a record at higher resolution than already available (Watts, 1985) from southern Italy for the Holocene and the Lateglacial and for the transition from glacial to Lateglacial floras. Earlier work at Monticchio (Watts, 1985) suffered from uncertainty about the reliability of radiocarbon dates (Appendix 1). The dates appeared too old and a source of old carbon in the sediments was suspected. A hypothesis was developed that carbon dioxide (CO,) may be being released into the lake from remnant volcanic activity. A test on living aquatic plants (Appendix 1) showed that submerged plants yield ‘old’ dates whereas emergent aquatic or marsh plants give modem dates. It was concluded that all dates on bulk sediment or on

macrofossils of aquatics may be unreliable. In the present study reliance has been placed on AMS (accelerator mass spectrometer) dates carried out on macrofossils (seeds and wood) of upland plants only. Monticchio is exceptional in preserving abundant volcanic ash (tephra) layers in its sediments. From approximately 15,000 BP to today a minimum of 21 easily recognisable airfall tephra horizons occur, the thickest being of 5 cm. The tephras are listed in Appendix 2. In contrast, the Rome area is less rich, with relatively few tephras. Lago di Martignano, for example, contains no visible tephras in the last 11,000 years. Tephras both document the activity of volcanoes within a region and permit dating by correlation with already dated deposits of volcanic origin at other sites. A further objective of the Monticchio study was to identify the impact of man on the forested landscape.

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W.A. Watts et al.: Vegetation History and Climate of the Last 15,000 Years There is evidence for occupation of the region far back into prehistory. Collections at Melfi (Muse0 Nazionale de1 Melfese) give evidence from grave goods of a very rich material culture of Greek and Etruscan aspect in the centuries before the extension of Roman power. The Roman period is recorded by many structures. In mediaeval times Melfi and its region was a centre of Norman and Hohenstaufen Imperial power and castle construction. At Monticchio the Abbey of Sant’ Ippolito on the lake shore dates from the 11-12th century. Now a ruin, it was succeeded by the Abbey of San Michele built in the 17th century at the base of a cliff overlooking the lakes. Whatever may have occurred during earlier prehistory, it may be assumed that from about 1000 B.C. to the decline in Roman power the forest was either cleared for cultivation or was managed for forest products. In mediaeval times the abbeys and the hunting culture of the Norman Kings and their Imperial successors may have favoured forest conservation and management more than clearance. These cultural effects may be recorded in the Monticchio pollen diagrams. THE SITE .4ND ITS SETTING The centre of the Italian Peninsula to the east of Naples is hilly to mountainous, several peaks reach 1800 to 2000 m. Monte Vulture (1326 m, 40”56’40” N, 3”lO’ 50” E) is both the highest point and the dominant feature of the eastern part of tlhe region. Situated in Basilicata Province the mountain is a now inactive volcano with two explosion crater lakes or maars, the Laghi di Monticchio, in its crater. The surface of the lakes lies at 656 m. The crater is intact on its eastern side, but is breached and degraded to the west where the lakes overflow by a small stream which has been deepened by an artificial channel. Monte Vulture is a Quaternary volcano with major activity between 0.66 and 0.58 Ma and a last episode within the crater dated to 0.13 Ma (Bonadonna et

Slation:

Monticchio

- 652

m

a.s.1.

al., 1993). It is the only volcano at the eastern margin of the Apennine chain. Some 100 km to the west near Naples there is a concentration of late Quatemary and modern volcanic activity, including such localities as Vesuvius, Ischia and the Phlegraean Fields. The region is subject to earthquakes, some of them very severe, the most recent in 1980. Monte Vulture is forested and the surrounding hilly country is a mosaic of cultivated land and patches of secondary woodland. The broad coastal plain to the east with Foggia at its centre is intensively cultivated with little natural vegetation. Cereals and vegetables are prois widespread on hill duced. Olea (olive) cultivation slopes to the east of Monte Vulture. Vitis (grape), Juglans (walnut), Custunea (sweet-chestnut), Corylus (hazelnut) and a variety of fruit-trees are also grown. The climate (Fig. 2) is winter-wet with a pronounced dry period in summer. The mean annual precipitation at the lakes is 815 mm of which 510 mm fall between October and March. The higher mountains of this region experience considerable snowfall and freezing. Visitors from northern Europe are surprised to find that this is a region for skiing and that chains are recommended for winter driving on icy roads. THE VEGETATION In the higher Apennines from north of Rome to the high mountains of Calabria the dominant tree is Fugus which usually forms the treeline. Juniper-us communis (common juniper) occurs in herbaceous vegetation above the treeline on higher mountains (nomenclature and plant distribution after Pignatti, 1982, English equivalents of Latin names after Polunin and Walters, 1985). Abies is absent as a native tree from this whole region, although it is frequently planted. The range of Picea (spruce) does not extend south of high mountains in the region of Florence. Beth is also northern in distribution, although

Station:

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80

60

JFMAMJJASOND

Period of observation:

JFMAMJJASONO

1930 - 1973

Number of years: 3 I Mean annual temperalure:

13.7 “C

FIG. 2. Monticchio:

Period of observation: 1920 - 1973 Number of years: 50 Mean annual precipitation: 815 mm Rainy days: 87

mean monthly temperature

and precipitation

data.

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a.s.l.

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aetnensis, a species similar to B. pendula, is endemic to Mount Etna in Sicily above 1200 m (Pignatti, 1982). The dominance of Fagus gives the higher Apennine forests a Central European aspect which is reinforced by the associated herb communities. Below the Fagus zone is a zone of mixed deciduous forest, rich in species. This includes Quercus species, of which the most important are Q. cerris, Q. pubescens and Q. frainetto, Acer (maple) including A. campestre, A. Tilia platyphyllos obtusatum and A. monspessulanum, (lime), and Fraxinus ornus (manna ash). Ostrya carpiniand Carpinus orientalis (oriental folia (hop-hornbeam) hornbeam) are also frequent in the region. Mixed deciduous forest lies between 1100 and 600 m on Monte Pollino on the boundary of Calabria and Basilicata provinces (Ltidi, 1946), although its upper and lower elevational limits vary with locality and aspect throughout southern Italy. Below the mixed deciduous forest and extending to the coast more characteristic ‘Mediterranean’ evergreen woodland occurs. Typical plants include Quercus ilex (holm oak), Pistacia spp., Phillyrea latifolia, Juniperus oxycedrus and Erica arborea (tree heath). With frequent burning, grazing and cutting this woodland degenerates into evergreen bush (‘maquis’) or evergreen dwarf shrub (‘garigue’). There are valuable general accounts of the vegetation in Ltidi (1946), Touring Club Italian0 (1958) and Polunin and Walters (1985). The forest above the Monticchio lakes is dominated by Fagus sylvatica and Quercus cerris. Fagus occupies damper areas close to the lakes. This is an unusually low elevation (ca. 700 m) for Fagus in southern Italy and its presence is probably related to the lake’s microclimate and to the presence of springs on the lower slopes of Monte Vulture. The shrub layer of the Fagus forest has abundant Ilex aquifolium (holly), Corylus avellana (hazel), Hedera helix (ivy) and Ruscus aculeatus (butcher’s-broom). The species-rich herbaceous flora includes

torminalis (wild service tree), Malus sylvestris (crab apple), Mespilus germanicus (medlar) and Prunus sp. (cherry) occur. There is very little evidence for ‘Mediterranean’ evergreen woodland at Monticchio apart from Quercus ilex. In the Ofanto River valley to the west, however, rock outcrops at about 300 m have large stands of Phillyrea latifolia with local Pistacia lentiscus, although these occur in an environment of mixed deciduous forest. True evergreen woodland and maquis are first encountered at lower elevations near the coast.

Mercurialis

113-185 cm 185-300 cm

Betula

ursinum

perennis,

Helleborus

foetidus,

Allium

and other species as reminiscent of Central Europe as of the Meditteranean. Quercus ilex occurs on cliffs above the lakes and on rock outcrops. Dry slopes at the rim of the crater have woodland of Quercus cerris, Q. pubescens and Carpinus orientalis. The woodlands are managed. Abies, which now occurs at the summit of Monte Vulture, results from planting in the early part of this century (Lopinto, 1988) and is not a natural occurrence. The same is true of Quercus pubescens woods on the outer slope of the crater. Alnus glutinosa (alder), is planted in lines on swampy ground beside the lake, although it must also have a natural origin. Alnus cordata, a large tree of southern Italy, occurs with Fagus further south in the region but was not observed at Monticchio. The outflow stream valley, and secondary forest on nearby slopes, contains rich mixed deciduous forest. In addition to the typical species already listed, Acer pseudo-platanus (sycamore), Carpinus betulus (hornbeam), Cornus mas (comelian cherry) Ulmus cf. U. glabra (wych elm), Ligustrum vulgare (privet), Euonymus europaeus (spindle) and the rosaceous trees,

Sorbus

STRATIGRAPHY

AND SEDIMENTS

The core reported here was taken in April 1993 in a fen at the margin of the larger lake, Lago Grande di Monticchio, at the southern side of the lake’s outflow drainage ditch. A core of 8.40 m was collected with a 7.5 cm diameter square-rod piston corer. The objective was to study the last 15,000 years at the site; much thicker sediments lie below and will be reported elsewhere. The most recent sediments are missing in the fen, probably because of artificial lowering of the lake level at some time in the recent past. To complete the Holocene history, mid-lake cores D, E and P from a major coring expedition in 1990 were used. Matching of cores was facilitated by the presence of tephra layers. In addition to processing of core samples for pollen-analysis, loss on ignition and carbonate content were measured. Tephra samples listed in Appendix 2 were taken for study, to be reported independently elsewhere. Samples were also taken for diatom analysis. Five centimetre core lengths were washed for macrofossil analysis (Fig. 4). The fen core

CORE A O-113 cm

300425

cm

425-547 547-840

cm cm

Very coarse loose fibrous peat. Not sampled. Coarse organic detritus. Lake mud, 40% organic, very variable in colour with much fine stratigraphic detail. Finely laminated grey to olive-grey lake mud, carbonate-rich. Grey to olive-grey fine detritus mud. Grey to olive-grey silt and clay, 10% organic. Frequent bands of bryophyte stems, usually without leaves.

CORE B (sampled beside A) 80-155 cm Coarse fibrous peat. Top 80 cm very coarse loose peat, could not be sampled and unsuitable for pollen-analysis. CORE D, E AND P (1990) Surface core P -20 to 30 cm. Core E O-194 cm. Core D 168-318 cm. The D, E and P cores were taken close together in the middle of the lake. The top of core E is datum. The

W.A. Watts et al.: Vegetation History and Climate of the Last 15,000 Years mud-water interface is 20 cm above datum. They overlap as indicated above. Th’ey are correlated using a tephra in the E and P cores at 26.5 cm and 7.5 cm respectively and by stratigraphic details. The sediments at Monticchio have been studied in detail by Zolitschka and Negendank (1996). Long sections of the mid-lake and probably also the fen core sediments are annually laminated. This and the large number of tephras give the larger Monticchio Lake an exceptional interest. The tephras after 15,000 BP are clustered at the end of the Full-glacial, during the Younger Dryus and at intervals in the Late H’olocene. Their major interest is as a dating tool because they can be correlated with known dated tephras elsewhere. Tephras are also known from marine cores off southern Italy (Paterne et aE., 1988) and from western Greece (St. Seymour and Christianis, 1995). Studies of the mid-lake D core show that most or all of the tephras originate in volcanoes of the Naples region (Narcisi, 1996), whereas maar lakes north of Rome have rather few tephras. In spite of the frequency of earthquakes in the region the sediments appear largely undisturbed. In the Fulli-glacial section of mid-lake cores from Monticchio, however, there are a number of turbidites which may have been triggered by earthquakes and the possibility of loss of some sediment by slumping to the middle of the lake cannot be overlooked.

THE POLLEN DIAGRAMS Figure 3 records the Lateglacial portion of the pollen diagram; Fig. 4 is a full Holocene and Lateglacial diagram from the fen core taken at the lake margin. Figure 5 documents approximately the last 3000 years from midlake cores. Figure 4 provides the most detailed pollen data with additional information on tephras, sediments and macrofossils, whereas Figs 3 and 5 are more summary in character. Single-grain or very rare occurrences are not included in the diagrams. The pollen sum includes all upland (non-aquatic) vascular plants with the exception of Alnus which is exclusively a shore and swamp tree. The pollen sum for most samples varied between 300 and 400 (maximum, 450, minimum, 250). Preservation was good to excellent at all levels with few crumpled or corroded specimens. Unknowns rarely exceeded 2%, an acceptable figure given the species-diversity of the Italian flora (4900 native species according to Webb, 1978). Figures 3 and 4 record1 tephras and radiocarbon dates. Figure 4 also records macrofossils, some algae, organic matter and carbonate (by loss on ignition at 550°C and 1000°C respectively, after Dean, 1974). The drafting of the dllagrams recognises some difficulties in nomenclature and in accurate determination. Pollen of Quercus ilex can be distinguished from other Quercus species in well-preserved specimens (Beug, 1961), but this is not always possible, especially where grains are not fully expanded or are crumpled. Quercus coccifera, which has Q. ilex-type pollen (Beug, 1961) does not occur in the southern mainland of Italy. The Quercus curve is for total Quercus and includes Q. ilex. The latter is also assigned a tentative, probably over-con-

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servative curve in Figs 4 and 5. It is certain that Q. ilex is always only a small part of total Quercus and that it is frequent in the last few thousand years but rare to absent earlier. A curve is also provided for total Oleaceae because of the variety of types present and the possibility of misidentification. Pollen morphology followed Beug (1961) and Punt et al. (1991). Total Oleaceae is broken down into Fruxinus ornus, Fruxinus excelsior-type, Phillyreu and Oleu in Figs 4 and 5. All of these taxa occur at or near Monticchio. Oleu is a frequent component of the pollen assemblages in zone la only (Fig. 5). Pollen of Fruxinus oxycurpu cannot be distinguished from that of F. excelsior (Beug, 1961); the latter does not occur in southem Italy. F. oxycurpu is rare locally, but can be seen by the Ofanto River. The other species are all common. Ligustrum vulgure, which is common locally, was not found as a fossil. Pollen of Carpinus betulus is distinctive, but pollen of Ostrya carpinifoliu and of Carpinus orientulis cannot be separated morphologically (Beug, 1961) and the two taxa are united as OstryalCurpinus orientalis type. Curpinus orientalis is common locally and may have supplied most of this pollen type. Ostryu is characteristic of mixed deciduous forests at lower elevations. Humulus (hop) and Cannabis (hemp) also have very similar to indistinguishable pollen, but as Hum&s is common on the shores of the larger Monticchio lake, it seems reasonable to identify it positively. Among herbs Plantago (plantain) has 14 species in Basilicata alone. No attempt was made to distinguish species comprehensively but there was considerable morphological diversity. Pollen referable to P. Zunceolutu and P. media made up the majority, especially in the late Holocene, but other types also occur. Rosaceous pollen was frequent, most of it referable to PotentiEZu-typebut types similar to Sorbus and Prunus also occur. Here too the necessity to collect adequate reference material in this large family rules out the possibility of a comprehensive study. Cereal-type pollen is distinguished from pollen of other grasses by its much greater size and possession of a broad annulus (Andersen, 1979). It is commonest in the Full-glacial ‘steppe’ flora. Clearly these must be wild grasses. Whether they are ancestral to cultivated cereals can only be guessed at. There is one Full-glacial occurrence, at 827 cm, of the distinctive pollen of Lygeum spartum (esparto grass, Drescher-Schneider, 1993), a species of Mediterranean steppe grassland in southern Italy and Spain (Polunin and Walters, 1985).

THE LATEGLACIAL The Lateglacial pollen-diagram (Fig. 3) illustrates the transition from the Full-glacial through Lateglacial to Holocene. The Full-glacial section of the diagram (zone 4) extends from 716 cm to the base. It is characterised by abundant pollen of Grumineue (grasses), Artemisiu and Chenopodiaceare. Pollen of Cupressaceae is also common and is presumed to be referable to a species of Juniperus, the only probable genus. Grass pollen grains of cereal size and morphology (Cereal-type) are common. Such vegeta-

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tion is usually assumed to be steppe, based on the abundant presence of Artemisia and Chenopodiaceae (van Zeist et al., 1975; van Zeist and Bottema, 1982). However, it is unusual to find co-occurrence of Juniper-us and Artemisia, either living or fossil, without the abundant presence of Pinus. In the western United States Juniper-us occidentalis occurs together with the shrub Artemisia tride.ntata (sage-brush) and grasses to form a shrub-steppe in parts of Oregon which have ca. 250 mm rainfall and where most precipitation falls in winter as snow (Franklin and Dyrness, 1973). This is a tempting, but geographically too distant, analogue for the vegetation and climate of Monticchio. Furthermore, nearly all European specie:5 of Artemisia are herbaceous. Fall (1992) records relatively high percentages of Juniperus with grass and some Pinus from pollen surface samples from sage-brush steppe in Colorado (U.S.A.). There are low to medium percentages of Juniperus (unnamed species, over 10% in many samples) with Artemisia in a late Holocene core frolmLake Galbasi (890 m) in southeastern Turkey, but it is accompanied by Quercus and Pinus in a degraded forest environment (van Zeist et al., 1970). Tree species of Juniperus in the Mediterranean region today (J. thurijkra, J. oxycedrus and J. excelsa) normally occur in low-elevation evergreen woodland or maquis (Polunin and Walters, 1985), and seem unlikely to have been present in the Full-glacial on climatic grounds. The Juniperus species may have been J. communis (common juniper), a widespread low shrub from alpine to lowland habitats which is recorded above the treeline on Monte Pollino by Liidi (1946). There are alpine as well as steppe species of Artemisia, a large genus. As an alternative to steppe there may have been a type of high-elevation alpine grassland of unusually dry aspect with Juniperus communis in zone 4. There are no extensive modem analogues for fossil vegetation of this type, but it is not unimaginable. Some Pinus pollen occurs but in relatively small quantities, usually less than 5%, a small percentage for a known large pollen producer. It seems likely that Pinus pollen arrived by long-distance transport. Several Pinus species occur today in local populations in southern Italy, such as Pinus leucodermis on Monte Pollino (Liidi, 1946). Similar small populations may have persisted during glacial time. The Monticchio lakes maintained high waterlevels at this time. It is difficult to speak of a water-table because the crater has springs on its slopes, but there was sufficient precipitation to replenish the lake with fresh water, an apparent inconsistency with a treeless upland. The end of Full-glacial zone 4 is rich in tephras. Preliminary study suggests that these originate in Campania but a full analysis of the mid-lake core D tephras is reported e&where (Narcisi, 1996). The sediment is largely inorganic, but diatom-rich. There are several horizons of felted matted bryophytes, usually leafless stems. At 716 cm Bet&a rises to a peak. An AMS date obtained on Betula fruits and bracts at this level is 12,540 f 130 BP. The Bet&a fmits can be assigned to B. pubes-

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tens. Associated with the Betula peak is a peak in Gramineae with rising Quercus. Fagus is already present Juniperus-type, Artemisia and at this level. Chenopodiaceae decline to low values. 690 to 7 16 cm is assigned to zone 3B. The BetulalGramineae peak marks the end of the Fullglacial. This brief episode ends with a rise in Quercus, followed by increases in Oleaceae (probably Fraxinus excelsior type), Ulmus, Acer and Fagus and a high peak (over 10%) of Tilia, probably T. platyphyllos (pollen morphology in Christensen and Blackmore, 1988) which is locally present today. These values for Tilia are exceptionally high given its low pollen production (Andersen, 1970) and are never achieved again. It must have been a major component of the forest. Similar Tilia peaks can be observed at Valle di Castiglione (Alessio et al., 1986) and at Lago di Martignano (Kelly and Huntley, 1991) where their age is not identified. The Tilia phase (zone 3A, 625-690 cm) ends with a reduction in or disappearance of mesic trees, including Quercus, and a new expansion of Betula and Artemisia. An AMS date of 10,460 f 60 BP is available from wood fragments between 578 and 588 cm. The date and the floristic regression point to a ‘Younger Dryas’ age for the flora. The sediments from 570 to 625 cm are assigned to zone 2, the ‘Younger Dryas’. At about 570 cm, Betula and Artemisia decline and disappear while Quercus becomes dominant with other deciduous trees. This indicates the beginning of the Holocene.

THE HOLOCENE The Holocene (zone 1) falls into four periods, the first, (zone Id), distinguished by dominance of Quercus and other deciduous trees, the second, (lc), similar to the first with the addition of frequent OstryalCarpinus orientalis. Zone lb has Abies, Carpinus betulus, Taxus and Alnus for the first time. In the fourth period Abies and Taxus become extinct and some elements of evergreen woodland appear, either through climatic causes or as a consequence of forest destruction by man. This zone (la) brings the record up to the present day. The Lateglacial ends at 570 cm (ca. 10,000 BP) when Betula, Artemisia and Chenopods fall to very low values or disappear from the pollen record. Quercus (deciduous species) is the dominant pollen taxon. Tilia and Fagus continue at low but significant values. The presence of Fagus in all pollen samples from the earliest Lateglacial to the present is an important constraint on climatic interpretation (Huntley et al., 1989), for, as discussed below, its presence is inconsistent with very low mean January temperatures. Quercus is accompanied by Ulmus which reaches high percentage values after 540 cm (to 10%). The other important taxa are Corylus and Oleaceae (Fraxinus spp. and Phillyrea). This appears to have been a mesic forest, although differing in character from that during the Lateglacial Interstadial with its much larger component of Tilia, Fagus and Acer. The climate distinction may lie in tbe mid-summer precipitation/evaporation

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ratio. At present there is a mid-summer rainfall minimum at Monticchio (Fig. 2). Orbital geometry (Kutzbach and Webb, 1993) points to higher insolation in summer during the first half of the Holocene with resulting warmer summers and cooler winters than today, peaking at 9000 BP. However, response surface estimates (see section on palaeoclimate) suggest a more complex picture with significantly colder winter temperatures than today and a longer period for growth (Fig. 7). Warmer summers in a climatic regime like today’s would increase summer water stress for mesic trees, whereas lower mean winter temperatures are less significant, for, with the exception of Phillyrea, all the taxa, at least at generic level, survive in the continental climates of eastern Poland and the Western Ukraine today. As the Holocene progresses Carpinus orientalis and/or Ostrya increase in abundance at the expense of Corylus to define zone lc. The flora was probably comparable to middle-elevation deciduous forest of today with only traces of evergreen woodland elements. The main change in the later Holocene (zone lc to lb) takes place between 290 and 270 cm. Abies appears at 290 cm followed by Taxus at 280 cm and Carpinus betulus at 270 cm. An AMS date of 3920 + 50 BP on an Abies seed from between 261 and 266 cm suggests ca. 4500 BP for the Abies invasion. Alnus, a lake-shore tree, had expanded a little earlier. This is a characteristic assemblage of the second half of interglacial cycles of which there are many examples, such as the Eemian at Grande Pile (Woillard, 1978). Iversen (1958) described a theoretical interglacial cycle in which late temperate (‘telocratic’) forest developed with increased rainfall, podsolised soils and expansion of heathland. Orbital considerations (Kutzbach and Webb, 1993) suggest that solar radiation increasingly resembled present day regimes in the later Holocene. Lower summer insolation may have resulted in a shorter growing period and a more favourable precipitation/evaporation ratio for droughtintolerant trees. Where did the components of the Abiesl CurpinuslTaxus forest come from? Abies was present in the northern Apennines throughout the Holocene (Lowe and Watson, 1993) but is present only as single pollen grains at Valle di Castiglione (Alessio et al., 1986) and at Lago di Martignano (Kelly and Huntley, 1991). These are low-elevation sites and it is possible that Abies migrated from north to south at a higher elevation in the Apennine chain. Alternatively, there may always have been residual populations in Calabria where natural populations occur today at middle elevations (Ltidi, 1946), and northward migration from Calabria may have been the source. Abies occurred at Monticchio, sometimes abundantly, in warmer episodes during the last glacial period (Watts, 1985) so that its survival locally in southern Italy throughout the glacial and post-glacial periods cannot be discounted. The topographic diversity of the region provides a wide range of habitats some of which may have favoured survival. More site studies will be required to clarify these problems. Both Southern Italy and the Balkans are possible refuge areas for temperate trees dur-

ing the late Quaternary (Huntley and Birks, 1983; Bennett et al., 1990). Quercus ilex first appeared in significant quantity during zone lc but was still greatly outnumbered by deciduous oaks. Its arrival may have been favoured by warmer winter temperatures. An AMS date of 2810 f 70 BP (on an Abies seed) at 171-176 cm records a time when Abies was still abundant. At 116-121 cm, when Abies values were falling steeply, an AMS date of 2460 f 60 BP on Nymphaea (white waterlily) seeds was obtained. Abies is still present macroscopically at this level. The date is credible, though some suspicion of an old-carbon effect attaches to all dates from aquatic plants or bulk sediments from Monticchio. The last phase of the Holocene (Zone la, Fig. 5) shows the decline to extinction of Abies and Tuxus. If we accept the 2460 BP date, then the extinctions took place over a few hundred years between about 2500 and 2200 years ago. The subsequent Holocene is distinguished by fluctuations in the percentages of Corylus, Carpinus orientalislOstrya and Carpinus bet&us. Fagus reaches it highest Holocene values, while trees and shrubs of the evergreen woodland appear. These include Pistacia, Ericaceae (probably Erica arborea, the only common ericaceous species of the region at present), and Olea. As there is a very limited local occurrence of evergreen woodland species today, it is probable that the appearance of their pollen is at least partly explained by long-distance transport. Quercus ilex is more abundant than before. Olea, probably the cultivated olive, has a peak at 184 cm, recording local olive groves. Juglans and Castanea both appear for the first time. Among the herbs, cereal-type pollen remains at low values but there is an increase in wild grasses, especially towards the surface. Plantago species, Rumex and Pteridium (bracken) probably indicate invasion of weeds after forest cutting. There is no very clear pattern of alternating periods of cutting and re-growth, but the general spread of weedy plants, plants of cultivation, and shrubs and trees of secondary woodland point to extensive forest clearance from the Roman period onward. As yet, however, there is insufficient information to link the diagram to any known archaeological events. The most obvious hypothesis to account for the disappearance of Abies and Taxus is forest destruction, assuming Taxus to be an understorey tree in an Abies-dominated community. It seems unlikely, however, that any forest type would be totally destroyed without leaving some remnants in inaccessible places, or that no effort would be made to conserve and manage Abies forest as a valuable resource. Yet Abies is completely absent as a native tree from Central and Southern Italy until Calabria is reached (Li.idi, 1946; Pignatti, 1982). Possibly there was a disease, such as affected Ulmus populations in northern Europe, or a climate change. Abies alba is even more sensitive to continental climate than Fugus and does not penetrate as far east in Central Europe. A small increase in summer dryness might have been sufficient to retard growth or reproduction. No certain answer can be given,

W.A. Watts et al.: Vegetation History and Climate of the Last 15,000 Years

but forest clearance may provide the most convincing explanation for the events recorded. The late Holocene contains two tephras. They are near enough to our own time to suggest possible known eruptions. The tephra at 115 cm in core E may be the 79 A.D. eruption of Vesuvius recorded by Pliny. A major eruption of 1631 A.D. (Belkin et al., 1983) may have been the source of the tephra at ‘7 cm in the E core. These suggestions are speculative. They require scientific confirmation. The tephras do not appear to have had any major effect on the vegetation or aquatic environment, although some were substantial. Similar observations of low longterm environmental impact have been reported in the case of the Laacher See Tephra in western Germany (Lotter and Birks, 1993).

PLANT

MACRO:FOSSIL

STRATIGRAPIIY

Data from plant macrofossils and sediment types are available from the fen-margin core (they are summarised in Fig. 4). Zone 4 is characterised by numerous small tephra falls and by bands of bryophyte debris, usually leafless stems of pleurocarpous mosses. The mosses appear to be predominantly Scorpidium scorpioides with some Culliergon sp., plants of fens rather than aquatics. A first hypothesis, that the mosses were killed on the lake shore by tephra falls and then floated to mid-lake was abandoned. There does not seem to be any precise relationship between tephras and moss layers. Alternatively, the deposition of mosses may be a response to small fluctuations in lake level with erosion of marginal vegetation. In the Lateglacial Interstadial (Zone 3) ostracods are common, although higher plant macrofossils are rare. Nymphaea occurs both as seed and pollen, but both are rare. The older Holocene I(zones Id, lc) has fruits and leafmargin bristles (‘hairs’) of Ceratophyllum demersum accompanied by N&s marina, indicating a development of rich benthic vegetation, confirmed by the occurrence of diatom species (see below) which are typical of shallow macrophyte-rich environments. From 410-500 cm the sediments are poor in seeds, but fish vertebrae and jaws occur and macroscopic filament balls of the bluegreen alga Gloeotrichia are common. Black bodies of a variety of shapes from spherical to polygonal or amorphous (The ‘Black Spheres’ of Fig. 4) and of about 10 microns in size are common in sediments from 400 to 650 cm. They are probably explained by pyrite or manganese precipitation. Sediments from 300425 cm are carbonate-rich. This may have been the most eutrophic phase in the lake’s recent history. Naias marina, accompanied later by N. minor, is replaced by Nymphaea in the macrofossil record above 266 cm. At this time the broad fringing band of large macrophytes which characterises the lake today became established. From 190 to 210 cm the sediments are extremely coarse and fibrous and contain almost no macrofossils. The fen must have grown over the lake margin at this time. !$ubsequently, new growth of

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Nymphaea, Potamogeton sp. and Cladium mariscus suggests a brief rise in the water-table once more before peat development ended the hydrosere at the coring site. Today the lake has a fringing band of Nymphaea alba. Ceratophyllum demersum, Potamogeton Zucens and Polygonum amphibium are common in shallow water (to 2 m). Naias species were not observed. Neither N. marina nor N. minor is recorded by Pignatti (1982) from southern Italy. In the swamp at the water’s edge Phragmites, Typha spp. and Scirpus Zacustris predominate. Cladium was not observed in today’s flora.

DIATOM

STRATIGRAPHY

Subsamples for diatom analysis were oxidized at room temperature in hydrogen peroxide and then washed repeatedly to remove oxidation by-products. Prepared samples were mounted in Naphrax, and 100 diatom valves were counted. The results are presented in Fig. 6. The base of the analysed sediments (zones 4 and 3, Full-glacial and Lateglacial Interstadial) is dominated by Cyclotella comensis and benthic Fragilaria spp., including primarily F. brevistriata, F. construens var. venter, and F. pinnata. Other benthic diatom species, such as Amphora ovalis var. afinis, Achnanthes minutissima, CymbeZZasilesiaca, and Eunotia curvata are also moderately abundant in the samples. This assemblage is typical of oligotrophic to mesotrophic lakes of low to moderate alkalinity, and many Lateglacial and early Holocene diatom stratigraphies are similarly dominated. The high percentages of benthic diatoms indicate significant littoral substrate for diatom colonization. Near the end of zone 3 CycZotelZacomensis percentages decline significantly, and in zone 2 (‘Younger Dryas’) it is absent from the sediments. The loss of the planktonic C. comensis may have resulted from a diversity of causes including lowered nutrient concentrations, significant shallowing of the lake, or high turbidity and thus reduced light availability for planktonic production. The loss-on-ignition results show no indication of a significant increase in sediment loading, and although benthic Fragilaria spp. increase at this time, the diatom data suggest a different limnological environment from the shallow fen that now occupies the site. Thus lowered nutrient concentrations seem the more probable explanation for the loss of planktonic diatoms. The upper unit of the analysed sediments (zone 1, Holocene) is characterised by benthic diatoms including benthic Fragilaria spp., Cocconeis placentula var. line-ata, Nitzschia amphibia, Gomphonema sp. affinity G. gracile, CymbeZZa cymbiformis, C. silesiaca, Eunotia curvata, and Amphora ovalis var. affinis. These diatoms are characteristic of a very shallowwater lake or marsh, and several species, particularly Cocconeis placentula var. lineta grow primarily on macrophytes. It is clear from the diatom stratigraphy that the modern-day fen originated during the Holocene.

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1

m--w

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.

20406080

.

.

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Percent FIG. 6. Monticchio

DISCUSSION: COMPARISON WITH VEGETATION HISTORY AT OTHER SITES IN EUROPE The classical Lateglacial pollen stratigraphy of northem Europe was established by Iversen (1954, 1973) and remains valid today, supported and expanded in detail by many studies. Iversen noted the difficulty of placing a boundary between Full-glacial and Lateglacial, but defined it, as did van der Hammen (1951), as the point where Artemisia percentages increase in the pollen-diagrams, taking this to indicate a rise in temperature during the growing season. This event defines the beginning of the ‘Oldest Dryas’. In southern France the Artemisia rise lasts from ca. 16,000 to 15,000 BP in cores from Les Echets near Lyons (de Beaulieu and Reille, 1984). It can also be seen, among other sites, at La Grande Pile in northeast France (Woillard, 1978; de Beaulieu and Reille, 1992). de Beaulieu and Reille (1992) consider the ‘Oldest Dryas’ to have been, climatically, ‘a crisis of aridity’. Evidence from Greenland ice cores shows that the ‘Oldest Dryus’, defined by high atmospheric dust concentrations (Mayewski et al., 1993), can be dated from ca. 17,000 to 14,500 BP. In Italy, pollen of Juniper-us-type characterises zone Y2, estimated to last from 18,000 to 14,000 years ago, at Valle di Castiglione (Alessio et d., 1986), but this is a time of low pollen concentration and the relatively high

Analyst S.C.Fritz

Fen: Diatom stratigraphy.

Juniperus-type percentages may be an artefact of low vegetation cover by other major pollen producers. Zone Y2 may on age grounds, be regarded as ‘Oldest Dryus’. At Monticchio the change from Full-glacial to Lateglacial conditions takes place at ca. 12,500 BP. No ‘Oldest Dryus’ is separately identifiable, for Juniperusrich vegetation extends far back into the Full-glacial (Watts, 1985). For the moment it seems best to consider the Full-glacial to have ended at 12,500 BP, leaving the delimitation of an ‘Oldest Dryas’ to future research. The steppe-like vegetation or shrub/grassland of the Full-glacial is similar to that recorded from Greece and Turkey (Bottema, 1979; Willis, 1992a; Tzedakis, 1993; van Zeist and Bottema, 1991), mainly from sites at low elevations. Similar vegetation is known from the Rome region (Alessio et al., 1986) and was earlier noted at Lago di Monterosi by Bonatti (1966). It appears to have extended from central and southern Italy through large areas of Greece and Turkey. At Monticchio, Boiling and Allerod, Iversen’s Lateglacial zones lb and 2, cannot be distinguished. The terminology is of limited value in southern Europe, other than to give broad indications of age and for comparability with northern Europe. The steep rise in Betulu and Gramineae (zone 3b) after 12,500 BP is the first clear evidence for climatic warming. The date corresponds with that for Boiling warming proposed by Iversen (1973). There is no identifiable brief climatic reversal

W.A. Watts et al.: Vegetation History and Climate of the Last 15,000 Years

(Iversen’s ‘Older Drya~:‘) from 12,000 to 11,700 BP, but the resolution of the pollen-diagram may not be sufficient to define it. The second phase of the Lateglacial Interstadial at Monticclnio (zone 3a) is characterised by abundant Tilia and other broad-leaved deciduous trees. Tilia peaks at Valle di Castiglione and at Martignano (Kelly and Huntley, 1991) may prove to correlate with the Monticchio peak if studied at higher resolution. The Tilia peak can be correlated in time with Iversen’s Allerod. No such flora is known outside Italy. Even in Italy, a record from Lago di Ganna (452 m) near Varese at the southern margin of the Alps, researched in meticulous detail by Schneid’er and Tobolski (1985), shows a largely alpine flora of Pinus species and herbs throughout the Lateglacial. The continuing presence of large alpine glaciers may have prod.uced this response in the vegetation. At Prato Spilla (1350 m) in the northern Apennines (Lowe, 1992) Tilia is also recorded from sediments identified as Lateglacial. It is accompanied by Quercus, Abies and Pinus in quantity. The ‘Younger Dryas’ (Iversen, 1973), is unrecorded in central and southern Italy except at Monticchio where its occurrence is quite clear. The nearest equally clear occurrences are in northern Italy, the Alpine region and southem France. It seems likely that it will be found at other sites in Italy if pollen diagrams are prepared at sufficiently close intervals to permit the necessary resolution of detail. A study of two contrasting sites in north-west Greece, north of Ioannina (Gramousti Lake, 285 m, and Rezina Marsh, 1800 m) and a consideration of other records in Greece by Willis (1992b) shows that the Lateglacial flora was steppe-dominated until the beginning of the Holocene, and that the classical Lateglacial sequence of Iversen is absent or debatable. The early Holocene at Monticchio was forested. In contrast, at Valle di Castiglione trees and shrubs made up less than 50% of the pollen sum until the mid-Holocene Chenopodiaceae and at about 5000 BP Artemisia, Gramineae were abundant in a diverse herb flora. They point to the presence of steppe-like grassland, perhaps over large areas of the lowlands, together with forest, mainly of Quercus and Corylus. Lago di Martignano (Kelly and Huntley, 1991) was forested with Quercus, Fagus and OstryalCarpinus orientalis in the earlier Holocene. The presence of forest at this site may be explained (Kelly and Huntley, 1991) by favourable moisture conditions created by a large lake and deeper crater than at Valle di Castiglione. The greater elevation, large lake, and steep-walled crater all favoured the presence of forest at Monticchio. The presence of Abies and Taxus in the late Holocene at Monticchio distinguishes it from low-elevation sites near Rome where Abzes is absent or present only as traces. Abies is present from the Lateglacial to the present at Prato Spilla (1350 m) in northern Italy (Lowe, 1992). It is also present through the Holocene at Rezina Marsh (1800 m) in northern Greece (Willis, 1992b) where both Abies alba and A. cephczlonica are recorded as macrofossils. There is a much lower percentage of Abies at the lowland Lake Gramousti site (Willis, 1992a). In both

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southern Italy and Greece Abies seems to have benefited from the higher precipitation and lower summer temperatures of middle elevatians in mountains. At Monticchio Quercus ilex is not present in significant quantity until the late Holocene, unlike the lowland sites where it is present throughout the Holocene. Olea is present as single pollen-grains only until pollen-zone la. Pistucia is recorded as a significant component of pollen percentages from eastern Mediterranean marine cores by et al. (1992), but is present only as isoRossignol-Strick lated single pollen-grains at Monticchio. The distinctiveness of the Monticchio record depends on elevation and remoteness from the coast. In contrast, Lago di Martignano records Quercus ilex, Olea, Ericaceae and Ostrya type, the common elements of low-elevation evergreen woodland, throughout the Holocene.

DISCUSSION: PALAEOCLIMATE RECONSTRUCTION$ Huntley and Prentice (1993) point to limitations on the reliability of pollen-based climate reconstructions in Europe including topographic diversity, lack of modem analogues for fossil floras and incomplete representation of the range of vegetation in the data-base of pollen surface samples. Nevertheless the method offers the possibility of more critical quantitative evaluation of data as a successor to intelligent guess-work about past floras and their climates based on ecological experience. Quantitative reconstructions of three climate variables have been made for Monticchio using pollen-climate response surface fitted to contemporary pollen and climate data (Bartlein et al., 1986; Huntley, 1993). The variables selected represent the principal constraints upon the distribution and abundance patterns of terrestrial higher plants in the temperate zone; they are (1) the mean temperature of the coldest month, (2) the annual temperature sum above a 5°C threshold, and (3) the ratio of actual to potential evapotranspiration. The results are presented in Fig. 7. The three lines indicate the value reconstructed as the mean of the 10 closest analogues and upper and lower standard errors of this mean; the selection of analogues was constrained to those representing the same biome as the fossil spectrum (Guiot et al., 1993; Huntley, 1993; Field et al., 1994). Climate reconstructions based upon herb-dominated pollen spectra are less secure than those based upon treedominated spectra in general and small changes in the relative frequencies of the principal herbaceous taxa may result in rapid and unrealistic changes in the reconstructed values (Huntley, 1994). The ‘spike’ in reconstructed values both of temperature sum and mean temperature of the coldest month that occurs near the base of the record (Fig. 7) reflects such an instability and should be ignored. The reconstruction thus indicates a glacial climate in zone 4 with a low temperature sum and with a marked deficiency of moisture supply to support the vegetation. Winter temperatures, however, are reconstructed to have been around -5 to -lO”C, values warmer than might have been expected and warmer than during the subsequent

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1

Lag0 Grande di Monticchio

: Pdaeoclimate

Core ‘PED’ 1

zi

reconstructions

Core MF93 I

I I

0.2

0.2

0.0 0

300

0

300

600

0.0 600

Depth (cm) FIG. 7. Monticchio Fen: Palaeoclimate reconstructions made from the pollen Reconstructions are presented for the short mid-lake core (P.E.D., Fig. 5) and the Fen-1993, Fig. 4). Three variables are reconstructed, the values shown being analogues plus the upper and lower standard errors of

phase of expansion of Bet&a when they fall near to -20°C. Although this may be an accurate reflection of the palaeoclimate changes, it seems unlikely that winters became colder at the transition from the Full-glacial to the Lateglacial Interstadial. Response surfaces fitted to European pollen data show that values of Cupressaceae (Juniperus-type) pollen greater than 10% occur principally in regions with winter temperatures -5°C or above (Huntley, 1990; B. Huntley, unpublished results), whilst peak abundances both of Artemisia and Chenopodiaceae centre around winter temperatures of -10°C (Huntley and Prentice, 1993); Betula pollen values in contrast peak around -15°C and below. Although the Lateglacial Interstadial period intuitively should have been warmer in winter than the preceding glacial stage, the best present analogues for the pollen spectra indicate the reverse. This may, as discussed previously, result from a lack of appropriate analogues from cold steppes.

data using climate response surfaces. fen core (Lag0 Grande Di Monticchio, the weighted mean of the ten closest this mean.

The Lateglacial Interstadial at Monticchio began when Bet&a and Quercus invaded largely herbaceous communities and replaced them. Response-surface derived temperatures for Betula and deciduous Quercus overlap around -8°C January mean, and 17”C, July mean (data in Huntley and Prentice, 1993). This was probably the temperature regime as the transition began. An annual precipitation of 700 mm or less can be assumed from the same data set. The present mean precipitation at Monticchio is 815 mm (Fig. 2). Fagus is present with Betula and Quercus from very early in the Interstadial. Its temperature optima are 2°C (January mean) and 21°C (July mean). It must have been growing near to its minimum requirements for temperature and moisture (Huntley et al., 1989). As the Interstadial progressed, a remarkable speciesrich mesic forest dominated by Tilia cf. T. platyphyllos evolved, pointing to rising mean summer temperatures

W.A. Watts ef al.: Vegetation History and Climate of the Last 15,000 Years and precipitation. The quantitative reconstructions indicate a rapid increase in moisture availability to levels comparable to those of today and a more gradual but sustained increase in annual temperature sum to peak values of more than 3500 degree-days at the time of the Tilia maximum. Coldest month temperatures also rise progressively to a maximum of ca. -5°C at the same time. The ‘Younger Dryas’ event is very distinctly marked by a return of birch with Artemisiu. Mesic trees fall to low levels (filiu, Fugus) or disappear temporarily (Acer). A reversion to the climate when the Betulu-Quercus invasion began can be assumed, but not to steppe or grassland climates, for many trees survived. Watts (1980) argued that there was no secure evidence for a ‘Younger Dryus’ event in southern and eastern Europe at a distance from the influence of the Atlantic. The new data from Monticchio show that this view was incorrect and was formed because of the inadequacy of the data then available. The magnitude of the reconstructed climate fluctuation during the ‘Younger Dryas’ is small with annual temperature sum dropping to ca. 3200 degree days and the mean temperature of the coldest month falling to ca. -7°C. Both variables subsequently return to values similar to those of the Lateglacial Interstadial at the transition of the Holocene. The Holocene clim,ate at Monticchio responded to orbital geometry. High’er summer insolation (Kutzbach and Webb, 1993) in the first half of the Holocene resulted in warmer summers than today. Winters, however, were cooler than today until after 6000 BP when, with insolation and seasonality approaching present conditions, they rose to values comparable to or even somewhat warmer than today. Moisture availability apparently also increased during the mid-Holocene. Abies, Tanus and Curpinus bet&us appeared and expanded. The present climate of Monticchio (Fig. 2) corresponds closely with response surface values for optimum performance of Abies, yet the species has become extinct locally. New site studies are required to establish the source and direction of the Holocene m&ration of Abies and the timing of other local extinctiorrs. A choice may then be made between the options, extinction due to climatic change (summer moisture deficiency), disease, or selective forest exploitation by man. The consistent presence of pollen of Quercus ilex during the later Holocene is reflected in the reconstruction of warmer winters (Fig. ‘7); the fluctuations in its pollen abundance largely account for the fluctuations in these reconstructed values. The reconstructions for the upper part of the mid-lake sediments (Fig. 7-PED) are consistent with those from the upper part of the fen core (Fig. 7-MF93). The most marked variations seen are once again those in the mean temperature of the coldest month. Values of ca. 0°C are reconstructed consistently after the fall in Abies pollen abundance and up to the level at which a number of herb pollen taxa increase near the top of the core. Whether these reconstructed variations in winter temperal.ures are realistic or an artefact is unclear. The variations in abundance of Q. ilex pollen and

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the disappearance of Abies both may reflect human management and/or destruction of the more mesic forests. Alternatively, however, we may infer that local human impact was negligible until the recent marked rise in abundance of pollen of herbaceous taxa; in this case it is likely that the reconstructed variations in winter temperatures are realistic.

ACKNOWLEDGEMENTS The 1993 fen core was collected by Watts, Allen and Huntley in April 1993. Diatom studies were carried out by Dr Sheri Fritz. Barbara C.S. Hansen of the University of Minnesota’s Limnological Research Centre carried out preliminary pollenanalysis of the Holocene in mid-lake cores taken with a Mackereth sampler by a University of Edinburgh team led by Professor K.M. Creer. She pointed out that the data available to her suggested that Monticchio contained a classical Lateglacial sequence. Dr M. Follieri of the University ‘La Sapienza’, Rome, gave valuable assistance with information and in the organization of field-work in Italy. Dr B. Narcisi of ENEA., Rome, has advised us on tephra studies, and provided us with climate data for Fig. 2. Dr H.F. Lamb is studying the tephras from the 1993 fen core. We value discussion of the sedimentology with Dr B. Zolitschka of the University of Trier. This work was carried out with the support of grants from the E.U. Euromaars Programme and the E.U. Epoch programme. We thank Colin Prentice, Joel Guiot, Pat Bartlein, Wolfgang Cramer and the many collaborators who have contributed pollen surface sample data used in deriving the response surfaces. REFERENCES Alessio, M., Allegri, L., Bella, F., Calderoni, G., Cortesi, C., Dai Pra, G., De Rita, D., Esu, D., Follieri, M., Improta, S., Magri, D., Narcisi, B., Petrone, V. and Sadori, L. (1986). ‘4c Dating, geochemical features, faunistic and pollen analyses of the uppermost 10 m core from Valle di Castiglione (Rome, Italy). Geologica Romana, 25,287-308. Andersen, S.Th. (1970). The relative pollen productivity of North European trees, and correction factors for tree pollen spectra. Danmarks Geologiske Undersagelse Series 2,%, 99 pp. Andersen, S.Th. (1979). Identification of wild grass and cereal pollen. Danmarks Geologiske Undersegelse, Yearbook 1978,69-92.

Bartlein, P.J., Prentice, I.C. and Webb, T. III (1986). Climatic response surfaces from pollen data for some eastern North American taxa. Journal of Biogeography, 13,35-57. De Beaulieu, J.-L. and Reille, M. (1984). A long Upper Pleistocene pollen record from Les Echets, near Lyon, France. Boreas, 13,111-132. De Beaulieu, J.-L. and Reille, M. (1992). The last climatic cycle at La Grande Pile (Vosges, France). A new pollen profile. Quaternary Science Reviews, 11,431-438.

Belkin, H.E., Kilbum, C.R.J. and De Vivo, B. (1993). Sampling and major element chemistry of the recent (A.D. 1631-1944) Vesuvius activity. Journal of Volcanology and Geothermal Research, 58,273-290.

Bennett, K.D., Tzedakis, P.C. and Willis, K.J. (1990). Quaternary refugia of north European trees. Journal of Biogeography, 18,103-115.

Beug, H.-J. (1961). Beitrage zur postglazialen Floren - und Vegetationsgeschichte In Sitddalmatien: Der See “Malo Jezero” auf Mljet. Teil II. Flora, 150,632-656. Bonadonna, F.P., Brocchini, D., Laurenzi, M.A., Principe, C. and Ferrara, G. (1993). Mt. Vulture Volcano. Chronostratigraphy and Paleogeographic Implications. In: Symposium: Quaternary Stratigraphy in Volcanic Areas, p. 13. INQUA Subcommission on European Quaternary Stratigraphy.

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Bonatti, E. (1966). North Mediterannean climate during the last Wtirm Glaciation. Nature, 209,984985. Bottema, S. (1979). Pollen analytical investigations in Thessaly (Greece). Palaeohistoria, 21, 194. Christensen, P.B. and Blackmore, S. (1998). Tiliaceae. In: Punt, W., Blackmore, S. and Clarke, G.C.S. (eds), The Northwest European Pollen Flora, Vol. V, pp. 33-43. Elsevier, Amsterdam. Dean, W.E., Jr (1974). Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss on ignition: Comparison with other methods. Journal of Sedimentary Petrology, 44,242-248. Drescher-Schneider, R. (1985). Analyse Palynologique dans Cahiers 1’Aspromonte en Calabre (Italie Meridionale). Ligures Prehistoire et de Protohistoire, N.U., 279-288. Drescher-Schneider. R. (1993). Funde nordafrikanischer Pollen in spat-und postglazialen Sedimenten am Siidrand der Alpen. Festschrift Zoller. Dissertationes Botanicae, 196, 415425. Fall, P.L. (1992). Spatial patterns of atmospheric pollen dispersal in the Colorado Rocky Mountains, USA. Review of Palaeobotany and Palynology, 74,293-313. Field, M.H., Huntley, B. and Miiller, H. (1994). Eemian climate fluctuation observed in a European pollen record. Nature, 371,779-783. Follieri, M., Magri, D. and Sadori, L. (1988). 250,000-year pollen record from Valle Di Castiglione (Roma). Pollen et Spores, 30,329-356. Follieri, M., Magri, D. and Narcisi, B. (1993). Palaeoenvironmental investigations on long sediment cores from volcanic lakes of Lazio (Central Italy) - An overview. Lecture Notes in Earth Sciences, 49,95-107. Francus, P., Leroy, S., Mergeai, I. and Seret, G. (1993). A multidisciplinary study of the Vito Maar sequence (Latium, Italy): Part of the last cycle in the Mediterranean area. Preliminary results. Lecture Notes in Earth Sciences, 49, 289-304. Springer, Berlin. Franklin, J.F. and Dymess, C.T. (1973). Natural vegetation of Oregon and Washington. U.S. Department of Agriculture, Forest Service, general technical report PNW-8. Griiger, E. (1977). Pollenanalytische Untersuchung zur Wiirmzeitlichen Vegetationsgeschichte von Kalabrien (StldItalien). Flora, 166,475-489. Guiot, J., De Beaulieu, J.L., Cheddadi, R., David, F., Ponel, P. and Reille, M. (1993). The Climate in Western Europe during the Last Glacial-Interglacial Cycle derived from Pollen and Insect Remains. Palaeogeography, Palaeoclimatology, Palaeoecology, 103,73-93. Van der Hammen, T. (1951). Late-Glacial flora and periglacial phenomena in the Netherlands. Leidse Geologische Mededelingen, 17,71-183. Huntley, B. (1990). European post-glacial forests: Compositional change in response to climatic change. Journal of Vegetation Science, 1,507-5 18. Huntley, B. (1993). The Use of Climate Response Surfaces to Reconstruct Palaeoclimate from Quatemary Pollen and Plant Macrofossil Data. Philosophical Transactions of the Royal Society of London, Series B - Biological Sciences, 341, 215-223. Huntley, B . ( 1994). Late Devensian and Holocene palaeoecology and palaeoenvironments of the Morrone Birkwoods, Aberdeenshire, Scotland. Journal of Quaternary Science, 9, 311-336. Huntley, B. and Birks, H.J.B. (1983). An Atlas Of Past and Present Pollen Maps for Europe: O-13,000 Years Ago. Cambridge University Press, Cambridge, 667 pp. Hdntley, B. and Prentice, I.C. (1993). Holocene Vegetation and Climates of Europe. In: Wright, H.E., Jr, Kutzbach, J.E., Webb, T. III., Ruddiman, W.F., Street-Perrott, F.A. and Bartlein, P.J., Global Climates Since the Last Glacial Maximum, University of Minnesota Press, Minneapolis, 569 pp.

Huntley, B., Bartlein, P.J. and Prentice, I.C. (1989). Climatic control of the distribution and abundance of beech (Fagus L.) in Europe and North America. Journal of Biogeography, 16,55 l-560. Iversen, J. (1954). The Late-Glacial flora of Denmark and its relation to climate and soil. Geological Survey of Denmark II, 80,87-119. Iversen, J. (1958). The bearing of glacial and interglacial epochs on the formation and extinction of plant taxa. In: Systematics of Today. Uppsala Universitets Arsskrifr, 1958, 6,210-215. Iversen, J. (1973). The development of Denmark’s nature since the Last-Glacial. Geological Survey of Denmark, V series, 7-C. 126 pp. Kelly, M.G. and Huntley, B. (1991). An ll,OOO-year record of vegetation and environment from Lago di Martignano, Latium, Italy. Journal of Quaternary Science, 6,209-224. Kutzbach, J.E. and Webb, T. III. (1993). Conceptual basis for understanding late-Quaternary climates, pp. 5-12. In: Wright, H.E., Jr, Kutzbach, J.E., Webb, T. III., Ruddiman, W.F., Street-Perrott, EA. and Bartlein, P.J., Global Climates Since the Last Glacial Maximum, University of Minnesota Press, Minneapolis, 569 pp. Lopinto, M. (1988). 11Monte Vulture nei suoi aspetti forestali e selvicolturali. Cellulosa e Carta, 39,44-54. Lotter, A.F. and Birks, H.J.B. (1993). The impact of the Laacher See Tephra on terrestrial and aquatic ecosystems in the Black Forest, southern Germany. Journal of Quaternary Science, 8,263-276. Lowe, J.J. (1992). Late-Glacial and early Holocene Lake Sediments from the Northern Apennines, Italy - Pollen stratigraphy and radiocarbon dating. Boreas, 21,193-208. Lowe, J.J. and Watson, C. (1993). Late-glacial and early Holocene pollen stratigraphy of the northern Apennines Italy. Quaternary Science Reviews, 12,727-738. Liidi, W. (1946). Die Gliederung der Vegetation auf der Apenninenhalbinsel insbesondere der montanen und alpinen In: Rikli, M. (ed.), Das Pflanzenkleid der Hohenstufen. Mittelmeerlander, Vol. 2, pp. 573-596. Hans Huber, Bern. Mayewski, P.A., Meeker, L.D., Whitlow, S., Twickler, M.S., Morrison, MC., Alley, R.B., Bloomfield, P. and Taylor, K. (1900). The atmosphere during the Younger Dryas. Science, 261,195-197. Narcisi, B.-M. (1996). Tephrochronology of a Late Quatematy lacustrine record from the Monticchio Maar (Vulture Volcano, Southern Italy). Quaternary Science Reviews, 15,155-165. Pateme, M., Guichard, F. and Labeyrie, J. (1988). Explosive activity of the South Italian volcanoes during the past 80,000 years as determined by marine tephrochronology. Journal of Volcanology and Geothermal Research, 34, 153-172. Pignatti, S. (1982). Flora d’ltalia (3 Vols.). Edagricole, Bologna. Polunin, 0. and Walters, M. (1985). A Guide to the Vegetation of Britain and Europe. Oxford University Press, 238 pp. Punt, W., Bos, J.A.A. and Hoen, P.P. (1991). Oleaceae. In: Punt, W. and Blackmore, S. (eds), The Northwest European Pollen Flora, Vol. VI, pp. 23-47. Elsevier, Amsterdam. Rossignol-Strick, M., Planchais, N., Pateme, M. and Duzer, D. (1992). Vegetation dynamics and climate during the deglaciation in the south Adriatic basin from a marine record. Quaternary Science Reviews, 11,415-423. St. Seymour, K. and Christianis, K. (1995). Correlation of a tepbra layer in western Greece with a late Pleistocene eruption in the Campanian province of Italy. Quaternary Research, 43,46-54. Schneider, R. and Tobolski, K. (1985). Lago di Ganna - Lateglacial and Holocene environments of a lake in the Southern Alps. In: Lang, G. (ed.), Swiss Lake and Mire Environments During The Last 15,000 Years, pp. 229-272. (Dissertationes Botanicae 87.) J. Cramer, Vaduz. Touring Club Italian0 (1958). Conosci l’ltalia, Vol. 2, La Flora. 272 pp. Touring Club Italiano, Milano.

W.A. Watts et al.: Vegetation History and Climate of the Last 15,000 Years Tzedakis, P.C. (1993). Long-term tree populations in northwest Greece through multiple Quatematy climatic cycles. Nature, 364,4374X). Watts, W.A. (1980). Regional variation in the response of vegetation to Lateglacial climatic events in Europe. In: Lowe, J.J., Gray, J.M. and lRobinson,J.E. (eds), Studies in the Lateglacial of North-west Europe, pp. l-22. Pergamon, Oxford. Watts, W.A. (1985). A long pollen record from Laghi di Monticchio, southern Italy: a preliminary account. Journal

131

Pollen Record For The Last 140,000 Years. Quaternary Research, 9, l-21.

Van Zeist, W., Timmers, R.W. and Bottema, S. (1970). Studies of modem and Holocene pollen precipitation in southeastern Turkey. Pulueohistoriu, 14,19-39. Van Zeist, W., Woldring, H. and Stapert, D. (1975). Late Quaternary vegetation and climate of southwestern Turkey. Palueohistoria,

14,53-143.

Van Zeist, W. and Bottema, S. (1982). Vegetational history of the Eastern Mediterranean and the Near East during the last 20,000 years. In: Palaeoclimates, Paleoenvironments and

of the Geological Society, 142,491499.

Webb, D.A. (1978). Flora Europaea. A retrospect. Taxon, 27,

Human Communities in the Eastern Mediterranean Region in later Prehistory. British Archaelogical Reports, International Series, 133,277-321.

3-14.

Willis, KJ. (1992a). The late Quaternary vegetational history of northwest Greece. 1. Lake Gramousti. New Phytologist, 121,

Van Zeist, W. and Bottema, S. (1991). Late Quatemary vegetation of the Near East. Beihefte zum Tiibinger Atlas des vorderen Orients. Series A Nr., 18, 156 pp. Zolitschka, B. and Negendank, J.F.W. (1996). Varve dating 76,300 years of lacustrine sedimentation. Quaternary

101-117.

Willis, K.J. (1992b). The late Quatemary vegetational history of northwest Greece. III. .4 comparative study of two contrasting sites. New Phytologist, 121, 139-155. Woillard, G.M. (1978). Grande Pile Peat Bog: A Continuous

Science Reviews, 15,101-112.

APPENDIX 1. RADIOCARBON DATES AMS dates, 1993 Fen Core *CAMS CAMS CAMS *CAMS CAMS CAMS CAMS

9858 9857 12,612 9856 12,611 12,610 9855

2460*60 2810 f 70 3920 * 50 6600*60 8590 f 50 10,460 + 60 12,540 f 130

116-121 171-176 261-266 266-272 378-383 578-588 711-716

cm cm cm cm cm cm cm

Nymphaea Seeds Abies Seeds Abies Seeds Nymphaea Seeds

Wood Fragments Wood Fragments Betula Seeds

*Possibly unreliable, especially 266-272 cm, because of old carbon error. Radiocarbon dates on modem plant material *BETA-64162 BETA64163 BETA-64164 *BETA44165

2040 f 113.2 f 112.1 f 7350 f

80 0.8% 1.1% 140

Ceratophyllum Foliage, Submerged Aquatic Nymphaea, Emergent Leaf Phragmites (Reed) Stem Myriophyllum Foliage, Submerged Aquatic

*Submerged foliage of living aquatic plants yields old dates due to old carbon error. Radiocarbon dates on bulk sediment (Watts, 1985) From 1982 Fen Core, taken in close proximity to the 1993 Core BETA-9152 QL-1883 BETA-7496 BETA-7497

18,290*280BP 21,200*5OOBP 23,840 +360 BP > 33,340 BP

All four dates are rejected because of old carbon error.

665-685 726-738 740-755 960-980

cm cm cm cm

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APPENDIX 2. MACROSCOPICALLY CORES P, E and D P/E E D

FEN CORE 214-215 cm 225-226 cm 252-254 cm 330-335 cm 573-574.5 cm 595 cm 600-603 cm 677-678 cm 685-686 cm 688-688.5 cm 698-700 cm 700-701 cm 713.5-714.5 cm 7 19-720 cm 729 cm 734 cm 744 cm 748.5 cm 752 cm 763 cm

6.5-7.5 cm 115-117 cm 316-318 cm 328-330 cm 372-373 cm

2 mm layer 2 mm layer 2 mm layer 2 mm layer 2 mm layer

VISIBLE TEPHRA LAYERS