A palynological study of environmental changes and their implication for prehistoric settlement in the Ilan Plain, northeastern Taiwan

Pollen records from two sediment cores taken from Ilan Plain, northeastern Taiwan provide new insights into the environmental and cultural history of the last 4200 years. The record indicates a relatively warm climate at around 4200 cal b.p. The environmental conditions would have been suitable for people whose settlements and activities were mainly in the littoral zone during this period. However, at ca. 3800 cal b.p., elements tolerant of brackish water dominated the vegetation, indicating that the environment was influenced by marine incursion. The remarkable increase in wetland flora suggests the presence of widespread marshlands thereafter. It is quite conceivable that settlement movement from the fluvial plain to hills between 3800 and 2400 cal b.p. can be correlated with the environmental changes in lowlands. A conspicuous gap in the archaeological sequence between 2400 and 1300 cal b.p. corresponds chronologically with a period of heavy rainfall or frequent typhoons as indicated by the aggradational episode in the Lanyang drainage basin as well as the flourishing of Alnus forests. The persistence of frequent landslides and climate deterioration would have had a dramatic impact on ancient humans and led to abandonment of the settlements. By 1300 cal b.p. a lowland flora is widespread indicating a shift from a marsh to a terrestrial environment in response to a well-developed fluvial plain. Decrease of landslides and the amelioration in climate could have advantages to human activities again. However, both the pollen and archaeological records indicate that intensive colonisation had a profound effect upon the vegetation within the Ilan region about 400 years ago.     

Vegetation history,climate and human impact over the last 15,000 years at Lago dell’Accesa (Tuscany,Central Italy)

Interdisciplinary studies of the sediments of Lago dell’Accesa started in 2001. We present here results from the palynological study. The pollen diagram provides a record of vegetation and climatic change spanning over 15,000 years. The oldest pollen spectra show a late-glacial steppe vegetation typical of central and southern Italy during this period. The Late-glacial Interstadial, interrupted by two cooling events, is dominated by open deciduous oak forests. The Younger Dryas is represented by 150 cm of sediment and shows the presence of steppic vegetation. The Holocene vegetation is characterised by alternating dominance of deciduous oaks and Quercus ilex. The three zones characterised by Q. ilex are accompanied by peat layers marking lake-level lowering at ca. 8600–7900, 4600–4300 and 3700–2800 cal b.p. Between approximately 9000 and 6000 cal b.p. extensive Abies-forests existed on the Colline Metallifere located 15–20 km to the north and northeast of the lake. Local fir populations may also have existed by the lake. Human impact starts at approximately 8000 cal b.p. during the Neolithic period, and increases at ca. 4300 cal b.p. Castanea and Juglans pollen is recorded from ca. 2800 cal b.p. The impact of the Etruscan settlement near the lakeshore is shown in the increasing values of arable crops, species of secondary forest canopy (Ericaceae, Pinus, Pistacia, Myrtus) and anthropogenic indicators (Chenopodiaceae, Plantago lanceolata, Rumex etc).     

Four thousand years of vegetation and fire history in the spruce forests of northern Kyrgyzstan (Kungey Alatau,Central Asia)

Analyses of pollen, macrofossils and microscopic charcoal in the sediment of a small sub-alpine lake (Karakol, Kyrgyzstan) provide new data to reconstruct the vegetation history of the Kungey Alatau spruce forest during the late-Holocene, i.e. the past 4,000 years. The pollen data suggest that Picea schrenkiana F. and M. was the dominant tree in this region from the beginning of the record. The pollen record of pronounced die-backs of the forests, along with lithostratigraphical evidence, points to possible climatic cooling (and/or drying) around 3,800 cal year b.p. and between 3,350 and 2,520 cal year b.p., with a culmination at 2,800–2,600 cal b.p., although stable climatic conditions are reported for this region for the past 3,000–4,000 years in previous studies. From 2,500 to 190 cal year b.p. high pollen values of P. schrenkiana suggest rather closed and dense forests under the environmental conditions of that time. A marked decline in spruce forests occurred with the onset of modern human activities in the region from 190 cal year b.p. These results show that the present forests are anthropogenically reduced and represent only about half of their potential natural extent. As P. schrenkiana is a species endemic to the western Tien Shan, it is most likely that its refugium was confined to this region. However, our palaeoecological record is too recent to address this hypothesis thoroughly.     

Late Holocene vegetation, fire, climate and upper forest line dynamics in the Podocarpus National Park, southeastern Ecuador

Late Holocene vegetation, fire, climate and upper forest line dynamics were studied based on detailed pollen and charcoal analyses. Two sediment cores, from the Rabadilla de Vaca mire (RVM) and the Valle Peque?o bog (VP), with an age of about 2100 and 1630 cal yrs b.p., respectively, were taken at the modern upper forest line in the Parque Nacional Podocarpus (Podocarpus National Park) in southeastern Ecuador. The two pollen records reflect relatively stable vegetation with slight changes in floral composition during the recorded period. Changes of the proportion between subpáramo and páramo vegetation are related to lower and higher frequency of fires. The RVM records show that the upper forest line moved to a higher elevation between 1630 and 880 cal yrs b.p., stabilising after 310 cal yrs b.p. Human impact is suggested by a high fire frequency, mainly between 1800–1600 and 880–310 cal yrs b.p. The VP records indicate no marked changes in the upper forest line. The charcoal records suggest an increased human impact from 230 cal yrs b.p. to the present. The results indicate that high fire frequency is an important factor in reducing the expansion of subpáramo vegetation and upper montane rainforest and in favouring the distribution of grass páramo. Since there is a clear correlation between fire and vegetation dynamics, it is difficult to detect how far climate change also played a significant role in upper forest line changes during the late Holocene.     

Prehistoric Pinus woodland dynamics in an upland landscape in northern Scotland: the roles of climate change and human impact

Pollen, microscopic charcoal, palaeohydrological and dendrochronological analyses are applied to a radiocarbon and tephrochronologically dated mid Holocene (ca. 8500–3000 cal b.p.) peat sequence with abundant fossil Pinus (pine) wood. The Pinus populations on peat fluctuated considerably over the period in question. Colonisation by Pinus from ca. 7900–7600 cal b.p. appears to have had no specific environmental trigger; it was probably determined by the rate of migration from particular populations. The second phase, at ca. 5000–4400 cal b.p., was facilitated by anthropogenic interference that reduced competition from other trees. The pollen record shows two Pinus declines. The first at ca. 6200–5500 cal b.p. was caused by a series of rapid and frequent climatic shifts. The second, the so-called pine decline, was very gradual (ca. 4200–3300 cal b.p.) at Loch Farlary and may not have been related to climate change as is often supposed. Low intensity but sustained grazing pressures were more important. Throughout the mid Holocene, the frequency and intensity of burning in these open Pinus–Calluna woods were probably highly sensitive to hydrological (climatic) change. Axe marks on several trees are related to the mid to late Bronze Age, i.e., long after the trees had died.     

Vegetation dynamics during the early to mid-Holocene transition in NW Malta, human impact versus climatic forcing

A pollen diagram was constructed for the early- to mid-Holocene transition (ca. 7350–5600 cal. b.p./5400–3650 b.c.) from the Burmarrad ria located in NW Malta. The vegetation at ca. 7350–6960 cal. b.p./5400–5010 b.c. was characterized by an almost tree-less steppe-like open landscape. Early Holocene dry climatic conditions were most probably due to intensification of the subtropical monsoon circulation that strengthened the subtropical anticyclonic descent over the central Mediterranean and blocked the penetration of humid air masses from the North Atlantic Ocean. At ca. 6950 cal. b.p./5000 b.c., the steppe-like vegetation was suddenly replaced by a Mediterranean evergreen forest or dense scrub dominated by Pistacia cf. lentiscus trees. This event, which has simultaneously been recorded in southern Sicily, was most probably caused by the southward shift of the ITCZ permitting the eastward movement of the North Atlantic cyclonic systems. Traces of human activities are evident in the pollen diagram since the beginning of the record but become more pronounced from the onset of the Temple Cultural Phase at ca. 6050 cal. b.p./4100 b.c. with a gradual decline of tree pollen. We suggest that the early- to mid-Holocene vegetation transformation was mainly controlled by a regional climatic change that occurred in a landscape only slightly impacted by human activities.     

From forest to open pastures and fields: cultural landscape development in western Norway inferred from two pollen records representing different spatial scales of vegetation

The cultural landscape development of a farming community in western Norway was investigated through pollen analyses from a lake and a peat/soil profile. The pollen record from the lake indicates that there was a decrease in arboreal pollen (AP) by the end of the Mesolithic period (ca. 4200 cal b.c.), and that a substantial forest clearance occurred during the Bronze Age (ca. 1500 cal b.c.). The latter, together with grazing indicators and cereals, suggests a widespread establishment of farming. At the beginning of the Roman Iron Age there is an increase in heath communities. The pollen diagram from the peat/soil profile shows the forest clearance in the Bronze Age more clearly than the lake profile. This local pollen diagram is compared with modern pollen samples from mown and grazed localities in western Norway. Both analogue matching and ordination (PCA) indicate that the site was characterised by pastures and cereal fields from the Late Bronze Age to the Late Iron Age. An expansion of cereal cultivation took place during the Pre-Roman Iron Age, and an arable field was established at the site after ca. a.d. 800. This investigation illustrates the potential of selecting pollen sites reflecting different spatial scales, and complements the cultural history of the area as inferred from archaeological and historical records.     

Holocene vegetation history with implications of human impact in the Lake Chaohu area, Anhui Province, East China

Palynological analyses of Holocene deposits located about 2 km to the southwest of the Lake Chaohu, Anhui Province, documented well the local vegetation history, its inferred environment and human impacts for the first time. An evergreen and deciduous mixed broad-leaved forest dominated by Cyclobalanopsis and Quercus existed from ca. 10,500 cal b.p. and became fully developed between ca. 8,250 and 7,550 cal b.p. Notable fluctuations occurred in the main components of the flora indicated by the decline in Cyclobalanopsis and other arboreal plants (AP), and an increase in terrestrial herbs between ca. 7,550 and 3,750 cal b.p., inferring the progressive opening of the forest under considerable human interference, which largely agrees with the archaeological evidence. After ca. 3,750 cal b.p., the broad-leaved forest largely gave way to terrestrial herbs, and never again recovered. Pinus continued to rise alongside the majority of herbs between ca. 3,750 and 2,000 cal b.p., then also declined after ca. 2,000 cal b.p. Human influence on the natural vegetation displayed in the pollen diagram seems to increase greatly up the core. The disappearance of broad-leaved forest indicates significant human impact after ca. 3,750 cal b.p., which is consistent with both the archaeological evidence and historical records. From that time the natural environment in the study area was subjected to long-standing pressure from increasing farming and population.     

Neolithisation at the site Brandwijk-Kerkhof, the Netherlands: natural vegetation, human impact and plant food subsistence

Brandwijk-Kerkhof (ca. 4600 to 3630 cal b.c.) is a Neolithic site, located on a river dune in the Dutch Rhine/Maas river area. The natural vegetation and human impact upon it have been investigated by analysis of pollen and macroremains from four cores that are located at increasing distances up to 20 m from the site. The relationship between the strength of human impact on the vegetation and the distance of the cores from the river dune has been investigated as well. The results show that the natural vegetation on top of the river dune consisted of deciduous woodland, while in the surrounding wetlands alder carr and eutrophic marsh vegetation dominated. Human impact of limited strength resulted in more open and disturbed vegetation. There is no correlation between the strength of the evidence of human impact in the pollen diagrams and the distance of the cores from the river dune. The evidence for presence of crop plants from the cores is compared with evidence from the excavation. The first presence of crop plants from ca. 4200 b.c. onwards corresponds with data from other Dutch wetland sites. Large-scale local crop cultivation cannot however be demonstrated. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A Holocene environmental record reflecting vegetation, climate, and fire variability at the Páramo of Quimsacocha, southwestern Ecuadorian Andes

We reconstructed the palaeoenvironmental conditions of the last ca. 8,000 years in the Tres Lagunas region of the Quimsacocha volcanic basin (ca. 3,800 m a.s.l.) in the southwestern Ecuadorian Andes. By means of a pollen and charcoal record, we analysed vegetation, fire, and climate history of this area, which is sensitive to climatic changes of both the Pacific as well as of the eastern Andes and Amazon region. Sediment deposits, pronounced increases of pollen and charcoal concentrations, and pollen taxa reflect warmer and drier conditions in the early to mid-Holocene (~8000 to 3900 cal. b.p.). During the late Holocene (2250 to −57 cal. b.p.), five warm and cold phases occurred at Quimsacocha. The most prominent cold phase possibly corresponds to the globally recognized Little Ice Age (LIA; ~600 to 100 cal. b.p.). The cold phase signal at Quimsacocha was characterized by a higher abundance of Poaceae, Iso?tes and Gentianella, which are favoured by cold and moist conditions. Frequent charcoal particles can be recorded since the early to mid-Holocene (~7600 b.p.). The high Andean tree species Polylepis underwent several phases of degradation and re-establishment in the basin, which could indicate the use of fire by pre-Columbian settlers to enhance the growth of preferred herb species. The Tres Lagunas record suggests that human populations have been influencing the environment around Quimsacocha since the last ca. 8,000 years.     

Late-glacial and Holocene vegetation history of the Magellanic rain forest in southwestern Patagonia,Chile

A ¹⁴C-dated high-resolution palaeoenvironmental record from a mire in southern Chile is used to reconstruct the Late-glacial and Holocene vegetation history of the Magellanic rain forest. The Late-glacial environment after around 15400–13500 cal b.p. was dominated by Gunnera magellanica, Nothofagus species (dombeyi type) and Gramineae (Poaceae) indicating an open parkland with cool and damp climatic conditions. At the end of the Late-glacial there was an increase in G. magellanica and a decline in Nothofagus dombeyi type. This ecological signal is interpreted as a result of a re-advance of the Gran Campo Nevado icefield, caused by either Younger Dryas cooling or a latitudinal shift of the southern Westerlies. After around 11250–10750 cal b.p. Nothofagus species, Drimys winteri and Embothrium coccineum expanded, indicating development of the Magellanic rain forest. At 4254±120 cal b.p. a tephra layer was deposited by the eruption of the Mt. Burney volcano leading to a long-term decline of the Nothofagus forest. A primary succession was then initiated, lasting for over 800 years before pre-eruption vegetation patterns redeveloped. In summary, our results indicate the extreme sensitivity of the Magellanic rain forest to climatic or volcanic impacts and the slow recovery of a mature forest after environmental changes.     

Early–Middle Holocene vegetation history, climate change and human activities at Lago Riane (Ligurian Apennines, NW Italy)

The radiocarbon-dated palaeoecological study of Lago Riane (Ligurian Apennines, NW Italy) presented here forms part of a wider investigation into the relationships between Holocene vegetation succession, climate change and human activities in the northern Apennines. The record of vegetation history from Lago Riane indicates that, since the end of the last glaciation, climate change and prehistoric human activities, combined with several local factors, have strongly influenced the pattern and timing of natural vegetation succession. The pollen record indicates an important change in vegetation cover at Lago Riane at ~8500–8200 cal. years b.p., coincident with a well-known period of rapid climate change. At ~6100 cal. years b.p., Fagus woodland colonised Lago Riane during a period of climate change and expansion of Late Neolithic human activities in the upland zone of Liguria. A marked decline in Abies woodland, and the expansion of Fagus woodland, at ~4700 cal. years b.p., coincided with further archaeological evidence for pastoralism in the mountains of Liguria during the Copper Age. At ~3900–3600 cal. years b.p. (Early to Middle Bronze Age transition), a temporary expansion of woodland at Lago Riane has been provisionally attributed to a decline in human pressure on the environment during a period of short-term climate change.     

Vegetation changes and human occupation in the Patagonian steppe, Argentina, during the late Holocene

Vegetation changes during the late Holocene are interpreted from four fossil pollen sequences from two caves at the Los Toldos archaeological locality, Santa Cruz province, Argentina. Taphonomic processes are particularly taken into account in order to analyze the effects on the fossil pollen records of biotic factors such as human occupation and animals, and abiotic ones such as volcanic ash fall. Fossil pollen assemblages are interpreted using local modern pollen data. The main vegetation change occurred at ca. 3750 uncal b.p., when a shrub steppe of Asteraceae subf. Asteroideae with Schinus, Ephedra frustillata and a high proportion of grasses was replaced by a shrub steppe of Colliguaja integerrima and Asteraceae subf. Asteroideae. This change is synchronous with an archaeological record change and could be related either to moderate climatic variations or the effects of ash fall on the environment. Plant communities similar to the present-day ones were established in the Los Toldos area from ca. 3750 uncal b.p.     

Postglacial vegetational and fire history: pollen, plant macrofossil and charcoal records from two Alaskan lakes

Pollen, plant macrofossil and charcoal analyses of sediments from two Alaskan lakes provide new data for inferring Lateglacial and Holocene environmental change. The records span the past 14,700 years at Lost Lake, 240 m a.s.l., central Alaska, north of the Alaska Range and 9600 years at Grizzly Lake, 720 m a.s.l., Copper River Plateau, south of the Alaska Range. Salix shrubs expanded in the herb tundra about 14,400 cal b.p., and Betula shrub tundra became established at ca. 13,200 cal b.p. Diminished Betula shrub cover in association with the increased abundance of herbaceous taxa occurred at 12,500–11,600 cal b.p., although the timing of these changes is not well constrained. Populus expanded at 11,200 cal b.p. and formed dense stands until 9600–9400 cal b.p. when Picea glauca forests or woodlands became established at both sites. The abundance of Alnus viridis increased markedly around 8500 cal b.p. at both sites, marking the development of alder shrub thickets around the lakes and on mountain slopes in these areas. Boreal forests dominated by Picea mariana became established around 7200 cal b.p. at Grizzly Lake and 5700 cal b.p. at Lost Lake. At Grizzly Lake, marked vegetational oscillations occurred within the past 8500 years; for example, A. viridis expanded at 2750 cal b.p. and 450 cal b.p. and declined at 150 cal b.p. Some of these oscillations coincide with large-scale climatic events, such as the Little Ice Age cooling (LIA), and they probably reflect vegetational sensitivity to climatic change at this high site. Microscopic charcoal at Lost Lake suggests that fire was important in the lateglacial birch tundra, probably because of severe moisture deficits of the regional climate and/or high abundance of fine fuels. On the basis of the Grizzly Lake microscopic charcoal record, regional fires were common between 8500 and 6800 cal b.p. and between 450 and 150 cal b.p. Around Grizzly Lake, the mean return intervals of local fires estimated from macroscopic charcoal were ∼386 years between 6800 and 5500 cal b.p. when Picea glauca dominated over P. mariana, ∼254 years between 5500 and 3900 cal b.p. when P. mariana was more abundant than P. glauca, and ∼200 years after 3900 cal b.p. in both P. glauca and P. mariana dominated forests. Correlation analysis of pollen and microscopic charcoal at Grizzly Lake reveals that increased fire activity led to the reductions of P. glauca, P. mariana, and tree Betula in association with the expansions of A. viridis, Epilobium, Lycopodium clavatum, and L. annotinum.     

A late Holocene pollen diagram from the Megaris,Greece, giving possible evidence for cultivation of<Emphasis Type="Italic"> Ceratonia siliqua</Emphasis> L. during the last 2000 years

A late Holocene pollen profile from the Megaris on the eastern Gulf of Corinth shows a vegetation which was strongly influenced by human impact throughout. A Pistacia-Phillyrea maquis, which is reflected in the older parts of the profile, changed later to a more degraded vegetation type. In the uppermost part Pinus dominates the pollen spectrum. A continuous record of Ceratonia siliqua pollen older than cal a.d. 100 is of special interest.     

Late Holocene environmental change and human impact inferred from three soil monoliths and the Laguna Zurita multi-proxi record in the southeastern Ecuadorian Andes

Late Holocene vegetation, climate and fire dynamics of mountain forest and paramo ecosystems, as well as human impact, are presented from the upper Rio San Francisco valley, southeastern Ecuadorian Andes. Palaeoenvironmental changes, inferred from three soil monoliths, spanning an altitudinal gradient between 1,990 and 3,200 m and the high resolution multi-proxy sediment record from Laguna Zurita (2,590 m), were investigated by pollen, spore and charcoal analyses, in combination with XRF- and magnetic susceptibility-scanning. Three of the four pollen records show a marked change in the floristic composition between ca. 900 and 350 cal b.p. (interpolated age). Past fires have strongly influenced the floristic composition of the mountain rainforest ecosystem. Frequent fires, together with the relatively high occurrence of grasses and some Zea mays plantations document past human activities in the upper Rio San Francisco valley. A large number of areas of probably ancient Z. mays cultivation in the upper Rio San Francisco valley has been identified, using GIS-based calculation. High occurrences of Cyperaceae and Isoetes indicate the development of marshy lake shores in response to a lower lake level at Laguna Zurita before ca. 700 cal b.p. The decrease of Isoetes and Cyperaceae after ca. 1200 cal b.p. reflects a lake level rise, due to increasing moisture and/or human activities.     

Holocene environmental history of Lake Vuolep Njakajaure (Abisko National Park, northern Sweden) reconstructed using biological proxy indicators

Holocene environmental and climatic changes are reconstructed using analyses of biological proxies in lake sediments from Vuolep Njakajaure, a lake located near the altitudinal treeline in northern Sweden (68°20′ N, 18°47′ E). We analysed biological proxy indicators from both aquatic and terrestrial ecosystems, including diatoms, pollen and chironomid head capsules, in order to reconstruct regional Holocene climate and the development of the lake and its catchment. During the early Holocene and after 2500 cal b.p., Fragilaria taxa dominated the diatom assemblages, whereas planktonic Cyclotella taxa prevailed during the major part of the Holocene (7800–2300 cal b.p.), indicating the importance of the pelagic habitat for diatom assemblage composition. The planktonic diatoms appeared at the same time as Alnus became established in the catchment, probably altering nutrient availability and catchment stability. The pollen record is dominated by mountain birch (Betula pubescens ssp. tortuosa) pollen throughout the Holocene, but high percentage abundances of Scots pine (Pinus sylvestris) pollen suggest the presence of a mixed pine-birch forest during the mid-Holocene (6800–2300 cal b.p.). Head capsules of Tanytarsini and Psectrocladius dominated the chironomid assemblage composition throughout the Holocene, in combination with Corynocera ambigua after 2300 cal b.p. A quantitative, diatom-based reconstruction of mean July air temperature indicated a relatively cold temperature during the early Holocene (9000–8000 cal b.p.) and after ca. 2300 cal b.p., whereas the mid-Holocene period is characterised by stable and warm temperatures. The overall patterns of Holocene climate and environmental conditions are similarly described by all biological proxy-indicators, suggesting relatively warm conditions during the mid-Holocene (ca. 7800–2300 cal b.p.), with a subsequent colder climate after 2300 cal b.p. However, the onset and magnitude of the inferred changes differ slightly among the proxies, illustrating different responses to lake development phases, land-uplift, and climate forcing (e.g., insolation patterns) during the Holocene in northern Sweden.     

Late-glacial and Holocene climate dynamics at the steppe/forest ecotone in southernmost Patagonia, Argentina: the pollen record from a fen near Brazo Sur, Lago Argentino

We present a pollen record from a fen at the eastern shore of Brazo Sur south of Lago Argentino, Argentina (core BRS 1/06, 50°34′54″S, 72°54′52″W, 198 m a.s.l.). The coring site is located in the transition zone from humid grass steppe to Andean Nothofagus forest. With the exception of a mid-Holocene sand layer, the record covers the interval between 13,350 and 1,700 cal b.p., indicating that there could have been no recurrence of Late-glacial conditions in Brazo Sur, as has been suggested in the literature as having been contemporary with the Younger Dryas interval in the northern hemisphere. The Late-glacial and early Holocene periods at Brazo Sur are characterized by fluctuations between humid grass-dominated steppe associations and drier ones dominated by Asteraceae and Ericaceae. At the start of the Holocene, the pollen influx increased. Nothofagus dominance began by 7,700 cal b.p. probably due to increasing moisture. Present-day closed Nothofagus forest developed around 2,500 cal b.p., related to a further increase in moisture.     

Elevational gradients during the Late-Glacial/Holocene vegetational transition in southern Bulgaria

The Late Glacial and early-Holocene vegetational history of a newly dated pollen and macrofossil diagram from Besbog, a cirque lake at 2250 m just above the forest limit in the Pirin Mountains of southwestern Bulgaria, is compared with a newly dated pollen diagram for the mire Shiroka Polyana at 1400 m in the conifer forest of the nearby Rhodope Mountains in order to investigate the chronology of major changes in the vegetation at different elevations. In the Lake Besbog record the non-arboreal pollen assemblage of the Late Glacial changed abruptly to that of Betula, Quercus and other deciduous types. The date for this change is about 11.6 ka cal b.p. The Quercus assemblage may be composed of pollen blown from intermediate elevations, to which deciduous forest had expanded because of higher summer temperatures related to high summer insolation. At Shiroka Polyana (1400 m) in the modern conifer belt, a similar change did not occur until about 8.8 ka cal b.p. The persistence of the dry steppe or steppe forest in the early Holocene at this lower site can also be attributed to high summer insolation. Thus as atmospheric temperature increased at the end of the Late Glacial, deciduous forests expanded first at intermediate elevations in the Pirin Mountains and only later in the Rhodope Mountains at lower elevations as summer insolation decreased.     

Late Quaternary vegetation history at Stracciacappa (Rome, central Italy)

The pollen diagram from Stracciacappa (Sabatini volcanic complex, Rome) provides a record of vegetational and climatic change spanning the last 60000 years, which is the time since when volcanic activity in the crater came to an end. The chronological framework of the sediment core is set by five AMS and three conventional radiocarbon dates; the mean sedimentation rate obtained by radiocarbon measurements was used to extrapolate the age of the record beyond the reach of ¹⁴C dating. The sequence from Stracciacappa provides results of fundamental importance for the understanding of the vegetational changes which occurred during the last pleniglacial period in central Italy, and it can be considered as a reference pollen record for the regional biostratigraphic characterization of this period. The site shows a high climatic sensitivity, particularly highlighted by the development of some pleniglacial oscillations with woodland, which interrupted the succession of steppe and grassland vegetational formations typical of the glacial periods. Unfortunately, due to sedimentation problems and alteration of the top level sediments, the Holocene is only recorded in part. Only for one millennium, from ca. 8300 to 7200 uncalb.p., was a real forest expansion characterized by over 90% arboreal pollen found.