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1.
The aim of this paper is to reconstruct the variation in the vegetation during the Holocene on the Northern Meseta through pollen analysis in order to determine the roles played by Pinus and Quercus in the vegetation dynamics. A new pollen sequence, Camporredondo, in the centre of the Duero River basin, Northern Meseta, Spain, is presented. It covers the period from ca 11,250 to 1630 cal yr BP. The Camporredondo sequence suggests that a forested landscape existed from the start of the Holocene with values of approximately 90% of arboreal pollen mainly derived from pine forests in the surroundings. Shortly after 8600 cal yr BP pine forests continued to dominate but the landscape became more open while stands of deciduous and evergreen Quercus developed. Around 4500 years ago, coinciding with the start of a period of less rainfall, the lacustrine areas in these territories began to silt up, favouring hydrophytic taxa such as Salix or Cyperaceae. A comparison with other Holocene pollen sequences from the central-eastern part of the Northern Meseta confirms the presence of pine forests in the whole region since the early Holocene. We discuss the variations of the general vegetation pattern in terms of the local or regional conditions at each site. Throughout the Holocene, Pinus forests dominated at least in the eastern half of the Duero River basin. The typical Holocene substitution of conifers by broadleaf species as recorded in other parts of the Iberian Peninsula and Europe, never takes place in the study area. The results of the present study suggest that the current view of the potential vegetation in the Spanish Northern Meseta should be reviewed.  相似文献   

2.
By mapping the data from 62 radiocarbon-dated pollen diagrams, this paper illustrates the Holocene history of four major vegetational regions in northeastern North America. Isopoll maps, difference maps, and isochrone maps are used in order to examine the changing patterns within the data set and to study broad-scale and long-term vegetational dynamics. Isopoll maps show the distributions of spruce (Picea), pine (Pinus), oak (Quercus), herb (nonarboreal pollen groups excluding Cyperaceae), and birch + maple + beech + hemlock (Betula, Acer, Fagus, Tsuga) pollen at specified times from 11,000 BP to present. Difference maps were constructed by subtracting successive isopoll maps and illustrate the changing patterns of pollen abundances from one time to the next. The isochrone maps portray the movement of ecotones and range limits by showing their positions at a sequence of times during the Holocene. After 11,000 BP, the broad region over which spruce pollen had dominated progressively shrank as the boreal forest zone was compressed between the retreating ice margin and the rapidly westward and northward expanding region where pine was the predominant pollen type. Simultaneously, the oak-pollen-dominated deciduous forest moved up from the south and the prairie expanded eastward. By 7000 BP, the prairie had attained its maximum eastward extent with the period of its most rapid expansion evident between 10,000 and 9000 BP. Many of the trends of the early Holocene were reversed after 7000 BP with the prairie retreating westward and the boreal and other zones edging southward. In the last 500 years, man's impact on the vegetation is clearly visible, especially in the greatly expanded region dominated by herb pollen. The large scale changes before 7000 BP probably reflect shifts in the macroclimatic patterns that were themselves being modified by the retreat and disintegration of the Laurentide ice sheet. Subsequent changes in the pollen and vegetation were less dramatic than those of the early Holocene.  相似文献   

3.
Quaternary deposits on the Pacific slope of Washington range in age from the earliest known interglaciation, the Alderton, through the Holocene. Pollen stratigraphy of these deposits is represented by 12 major pollen zones and is ostensibly continuous through Zone 8 over more than 47,000 radiocarbon yr. Before this, the stratigraphy is discontinuous and the chronology less certain. Environments over the time span of the deposits are reconstructed by the comparison of fossil and modern pollen assemblages and the use of relevant meteorological data. The Alderton Interglaciation is characterized by forests of Douglas fir (Pseudotsuga menziesii), alder (Alnus), and fir (Abies). During the next younger interglaciation, the Puyallup, forests were mostly of pine, apparently lodgepole (Pinus contorta), except midway in the interval when fir, western hemlock (Tsuga heterophylla), and Douglas fir temporarily replaced much of the pine. Vegetation outside the limits of Salmon Springs ice (>47,00034,000 yr BP) varied chiefly between park tundra and forests of western hemlock, spruce (Picea), and pine. The Salmon Springs nonglacial interval at the type locality records early park tundra followed by forests of pine and of fir. During the Olympia Interglaciation (34,00028,000 yr BP), pine invaded the Puget Lowland, whereas western hemlock and spruce became manifest on the Olympic Peninsula. Park tundra was widespread during the Fraser Glaciation (28,00010,000 yr BP) with pine becoming more important from about 15,000 to 10,000 yr BP. Holocene vegetation consisted first of open communities of Douglas fir and alder; later, closed forests succeeded, formed principally of western hemlock on the Olympic Peninsula and of western hemlock and Douglas fir in the Puget Lowland. Over the length of the reconstructed environmental record, climate shifted between cool and humid or relatively warm, semihumid forest types and cold, relatively dry tundra or park tundra types. During times of glaciation, average July temperatures are estimated to have been at least 7°C lower than today. Only during the Alderton Interglaciation and during the Holocene were temperatures higher for protracted periods that at present.  相似文献   

4.
At White Pond near Columbia, South Carolina, a pollen assemblage of Pinus banksiana (jack pine), Picea (spruce), and herbs is dated between 19,100 and 12,800 14C yr B.P. Plants of sandhill habitats are more prominent than at other sites of similar age, and pollen of deciduous trees is infrequent. The vegetation was probably a mosaic of pine and spruce stands with prairies and sand-dune vegetation. The climate may have been like that of the eastern boreal forest today. 14C dates of 12,800 and 9500 yr B.P. bracket a time when Quercus (oak), Carya (hickory), Fagus (beech), and Ostrya-Carpinus (ironwood) dominated the vegetation. It is estimated that beech and hickory made up at least 25% of the forest trees. Conifers were rare or absent. The environment is interpreted as hickory-rich mesic deciduous forest with a climate similar to but slightly warmer than that of the northern hardwoods region of western New York State. After 9500 yr B.P. oak and pine forest dominated the landscape, with pine becoming the most important tree genus in the later Holocene.  相似文献   

5.
Hager Pond, a mire in northern Idaho, reveals at least five pollen zones since sediments formed after the last recession of continental ice (>9500 yr BP). Zone I (>9500-8300 yr BP) consists mainly of diploxylon pine, plus low percentages of Abies, Artemisia, and Picea. SEM examination of conifer pollen at selected levels in the zone reveals that Pinus albicaulis, P. monticola, and P. contorta are present in unknown proportions. The zone resembles modern pollen spectra from the Abies lasiocarpa-P. albicaulis association found locally today only at high elevation. Presence of whitebark pine indicates a cooler, moister climate than at present, but one which was rapidly replaced in Zone II (8300-7600 yr BP) by warmer, drier conditions as inferred by prominence of grass with diploxylon pine. Zone III (7600-3000 yr BP) was probably dominated by Pseudotsuga menziesii, plus diploxylon pine and prominent Artemisia and denotes a change in vegetation but continuation of the warmer drier conditions. Beginning at approximately 3000 yr BP Picea engelmannii, Abies lasiocarpa, and/or A. grandis and diploxylon pine were dominants and the inferred climate became cooler and moister concomitant with Neoglaciation. The modern climatic climax (Zone V), with Tsuga heterophylla as dominant, has emerged in approximately the last 1500 yr.  相似文献   

6.
An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ∼12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred > 15,400 cal yr BP. The earliest known vegetation to develop on the island (∼12,900 cal yr BP) was pine woodland (Pinus contorta) with alder (Alnus), sedges (Cyperaceae) and ferns (Polypodiaceae type). By ∼12,240 cal yr BP, Sitka spruce (Picea sitchensis) began to colonize the island while pine woodland declined. By ∼11,200 cal yr BP, mountain hemlock (Tsuga mertensiana) began to spread across the island. Sitka spruce-mountain hemlock forests dominated the lowland landscapes of the island until ∼10,180 cal yr BP, when western hemlock (Tsuga heterophylla) began to colonize, and soon became the dominant tree species. Rising percentages of pine, sedge, and sphagnum after ∼7100 cal yr BP may reflect an expansion of peat bog habitats as regional climate began to shift to cooler, wetter conditions. A decline in alders at that time suggests that coastal forests had spread into the island's uplands, replacing large areas of alder thickets. Cedars (Chamaecyparis nootkatensis, Thuja plicata) appeared on Mitkof Island during the late Holocene.  相似文献   

7.
Kylen Lake, located within the Toimi drumlin field, is critically positioned in relation to Late Wisconsin glacial advances, for it lies between the areas covered by the Superior and St. Louis glacial lobes between 12,000 and 16,000 yr B.P. The pollen and plant-macrofossil record suggests the presence of open species-rich “tundra barrens” from 13,600 to 15,850 yr B.P. Small changes in percentages of Artemisia pollen between 14,300 and 13,600 yr B.P. appear to be artifacts of pollen-percentage data. Shrub-tundra with dwarf birch, willow, and Rhododendron lapponicum developed between 13,600 and 12,000 yr B.P. Black and white spruce and tamarack then expanded to form a vegetation not dissimilar to that of the modern forest-tundra ecotone of northern Canada. At 10,700 B.P. spruce and jack pine increased to form a mosaic dominated by jack pine and white spruce on dry sites and black spruce, tamarack, and deciduous trees such as elm and ash on moist fertile sites. At 9250 yr B.P. red pine and paper birch became dominant to form a vegetation that may have resembled the dry northern forests of Wisconsin today. The diagram terminates at 8410 ± 85 yr B.P. Climatic interpretation of this vegetational succession suggests a progressive increase in temperature since 14,300 yr B.P. This unidirectional trend in climate contrasts with the glacial history of the area. Hypotheses are presented to explain this lack of correspondence between pollen stratigraphy and glacial history. The preferred hypothesis is that the ice-margin fluctuations were controlled primarily by changes in winter snow accumulation in the source area of the glacier, whereas the vegetation and hence the pollen stratigraphy were controlled by climatic changes in front of the ice margin.  相似文献   

8.
At Green Pond, a small permanent sinkhole pond in Bartow County, northwest Georgia, organic silty clays are buried by up to 2 m of colluvium. Pollen from the clays shows that a Pinus-Quercus-herb (pine-oak-herb) flora was present before 29,630 radiocarbon yr ago. It is interpreted as the product of a xeric woodland with prairie-like openings. Between 29,630 and approximately 25,000 BP, pollen of Pinus and herbs was sparse; Quercus and Carya (hickory) predominated in the pollen rain. There were few other deciduous trees. Oak-hickory forest is thought to have been present. From 25,000 to 23,000 BP, more diverse forest with pines and some Picea (spruce) became established. At the same time Taxodium (swamp cypress) was locally abundant, as were shrubs characteristic of Coastal Plain swamps. Some time after 23,000 BP, the pond basin filled with colluvium and no further sedimentation took place, other than thin muck sedimented on the bottom of the present Green Pond.The sediments were first thought to be of Sangamon age because the pollen sequence has many of the characteristics of an interglacial cycle, but the radiocarbon dates correlate them firmly with the Farmdalian Interstadial. A comparison with known Farmdalian sites is made, but the important sites are in the northern United States and adjacent Canada, too far away to make a useful comparison of the details of pollen diagrams from the two areas. At another Bartow County pond site, Bob Black Pond (Watts, 1970), a flora predominantly of pine with spruce and oak was present immediately before 22,900 BP and a strikingly cold flora with jack-pine, spruce and northern herbs followed immediately after. The radiocarbon dates indicate that the sedimentary sequence at Bob Black Pond immediately follows that at Green Pond.  相似文献   

9.
This study investigated Holocene tree‐line history and climatic change in the pre‐Polar Urals, northeast European Russia. A sediment core from Mezhgornoe Lake situated at the present‐day alpine tree‐line was studied for pollen, plant macrofossils, Cladocera and diatoms. A peat section from Vangyr Mire in the nearby mixed mountain taiga zone was analysed for pollen. The results suggest that the study area experienced a climatic optimum in the early Holocene and that summer temperatures were at least 2°C warmer than today. Tree birch immigrated to the Mezhgornoe Lake area at the onset of the Holocene. Mixed spruce forests followed at ca. 9500–9000 14C yr BP. Climate was moist and the water level of Mezhgornoe Lake rose rapidly. The hypsithermal phase lasted until ca. 5500–4500 14C yr BP, after which the mixed forest withdrew from the Mezhgornoe catchment as a result of the climate cooling. The gradual altitudinal downward shift of vegetation zones resulted in the present situation, with larch forming the tree‐line. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

10.
A peat layer beneath two till beds was found at Seitevare in Swedish Lapland. The pollen flora layer indicates deposition during the later part of the Eemian Interglacial. The vegetation consisted of open forests predominated by pine and birch, mixed with alder and spruce. The sedimentation took place in a small oligotrophic-dystrophic water basin with a pH about 5, according to the diatom flora. In an adjacent section, silty sediments with pollen indicating interstadial vegetation (birches, herbs) are covered by one till bed. These sediments are tentatively correlated with the Peräpohjola Interstadial in northern Finland and north-eastern Sweden. The lithostratigraphy indicates one pre-Eemian and probably three Weichselian glacial advances.  相似文献   

11.

The first radiocarbon-dated pollen record from the Mamakan section is presented. This record has become the basis for the reconstruction of the vegetation and climate of the Middle Holocene in the Mamakan archaeological area, where a number of well-known Siberian archaeological sites of the Late Mesolithic–Middle Bronze period are located. Reconstructions suggest that sparse spruce and larch stands dominated in the area between 6450 and 6150 cal BP. Later, from 6150 to 4700 cal BP, Scots pine began to spread in a warmer climate than before, following the general trend of its expansion in the southern part of Eastern Siberia. A cooler climate than previously with increased soil and air humidity occurred in the Mamakan region from 4700 to 3840 cal BP, causing the regional expansion of Siberian pine. The time interval from 3840 to 3600 cal BP was characterized by the significant development of pine, spruce, and larch forests. On the basis of the age model, we assume that, in the lower reaches of the Vitim River and, probably, in other mountain regions north of Lake Baikal, Scots pine spread about 600 years later than in the Cis-Baikal region and east of the lake. This transition from dark coniferous-taiga to light coniferous-taiga with a predomination of Scots pine signifies the most fundamental change in vegetation of the Baikal region in the Holocene. This is often discussed as one of the possible causes of the Middle Neolithic cultural hiatus (6660–6060 cal BP), which has been documented in the archaeological records from different parts of this vast region. Reconstruction of vegetation in the Mamakan region suggests that the territory of the Nizhnii Vitim River has been favorable for humans during most of the hiatus recorded in the Cis-Baikal area and may have been considered as a refuge for populations of hunter-gatherers in the Middle Neolithic.

  相似文献   

12.
A pollen analytical investigation of the sediments of Berry Pond, Berkshire County, Massachusetts, has demonstrated a sequence of pollen assemblage zones similar to those detected elsewhere in New England. From about 13,000 to 12,000 yr B.P. the vegetation of the region was treeless, probably tundra. By 11,500 yr tundra had been replaced by open boreal forest. Closed boreal forest became dominant by 10,500 yr. Boreal forests were replaced by mixed coniferous and deciduous forests with much white pine about 9600 yr ago. A “northern hardwoods” complex with much hemlock, beech, and sugar maple succeeded the mixed forests 8600 yr ago. Hemlock declined very rapidly approximately 4800 yr ago and was replaced by birch, oak, beech, ash, and red maple. This decline may have been biologically rather than climatically induced. There is a slight maximum of pine (much of it pitch pine) from 4100 to 2600 yr ago, perhaps indicative of warmer and/or drier conditions. There were slight changes in the forests about 1600 yr ago as chestnut immigrated and spruce and larch increased slightly. European land clearance and subsequent land abandonment are detectable in the uppermost levels.  相似文献   

13.
A new record from Potato Lake, central Arizona, details vegetation and climate changes since the mid-Wisconsin for the southern Colorado Plateau. Recovery of a longer record, discrimination of pine pollen to species groups, and identification of macrofossil remains extend Whiteside's (1965) original study. During the mid-Wisconsin (ca. 35,000-21,000 yr B.P.) a mixed forest of Engelmann spruce (Picea engelmannii) and other conifers grew at the site, suggesting a minimum elevational vegetation depression of ca. 460 m. Summer temperatures were as much as 5°C cooler than today. During the late Wisconsin (ca. 21,000-10,400 yr B.P.), even-cooler temperatures (7°C colder than today; ca. 800 m depression) allowed Engelmann spruce alone to predominate. Warming by ca. 10,400 yr B.P. led to the establishment of the modern ponderosa pine (Pinus ponderosa) forest. Thus, the mid-Wisconsin was not warm enough to support ponderosa pine forests in regions where the species predominates today. Climatic estimates presented here are consistent with other lines of evidence suggesting a cool and/or wet mid-Wisconsin, and a cold and/or wet late-Wisconsin climate for much of the Southwest. Potato Lake was almost completely dry during the mid-Holocene, but lake levels increased to near modern conditions by ca. 3000 yr B.P.  相似文献   

14.
Pollen productivity is one of the most critical parameters for pollen–vegetation relationships, and thus for vegetation reconstruction, in either pollen percentages or pollen accumulation rates. We obtain absolute pollen productivity of three major tree types in northern Finland: pine (Pinus sylvestris), spruce (Picea abies) and birch (Betula pubescens ssp. pubescens and B. pubescens ssp. czerepanovii treated as one taxon). Long‐term monitoring records of pollen traps from 15 sites (duration: 5–23 years) and tree volume estimates within a 14 km radius of each trap were compared to estimate pollen productivity (grains m?3 a?1) of these trees using a regression method. The slope of the linear relationship between pollen loading and distance‐weighted plant abundance represents pollen productivity. Estimated productivities of pollen (×108 grains m?3 a?1) for pine, spruce and birch are 128.7 (SE 31.5), 341.9 (SE 81.3) and 411.4 (SE 307.7), respectively. The birch estimate (P > 0.05) is not as good as the others and should be used with caution. Pollen productivities of pine, spruce and birch in northern Finland are, in general, comparable to those of congeneric species in other regions of Europe and Japan. Although the year‐to‐year variations are significant, our volume‐based estimates of pollen productivity for pine and spruce will be essential for quantitative reconstruction of vegetation in the region. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

15.
The paucity of low- and middle-elevation paleoecologic records in the Northern Rocky Mountains limits our ability to assess current environmental change in light of past conditions. A 10,500-yr-long vegetation, fire and climate history from Lower Decker Lake in the Sawtooth Range provides information from a new region. Initial forests dominated by pine and Douglas-fir were replaced by open Douglas-fir forest at 8420 cal yr BP, marking the onset of warmer conditions than present. Presence of closed Douglas-fir forest between 6000 and 2650 cal yr BP suggests heightened summer drought in the middle Holocene. Closed lodgepole pine forest developed at 2650 cal yr BP and fires became more frequent after 1450 cal yr BP. This shift from Douglas-fir to lodgepole pine forest was probably facilitated by a combination of cooler summers, cold winters, and more severe fires than before. Five drought episodes, including those at 8200 cal yr BP and during the Medieval Climate Anomaly, were registered by brief intervals of lodgepole pine decline, an increase in fire activity, and mistletoe infestation. The importance of a Holocene perspective when assessing the historical range of variability is illustrated by the striking difference between the modern forest and that which existed 3000 yr ago.  相似文献   

16.
High‐resolution pollen, plant macrofossil and sedimentary analyses from early Holocene lacustrine sediments on the Faroe Islands have detected a significant vegetation perturbation suggesting a rapid change in climate between ca. 10 380 cal. yr BP and the Saksunarvatn ash (10 240±60 cal. yr BP). This episode may be synchronous with the decline in δ18O values in the Greenland ice‐cores. It also correlates with a short, cold event detected in marine cores from the North Atlantic that has been ascribed to a weakening of thermohaline circulation associated with the sudden drainage of Lake Agassiz into the northwest Atlantic, or, alternatively, a period with distinctly decreased solar forcing. The vegetation sequence begins at ca. 10 500 cal. yr BP with a succession from tundra to shrub‐tundra and increasing lake productivity. Rapid population increases of aquatic plants suggest high summer temperatures between 10 450 and 10 380 cal. yr BP. High pollen percentages, concentrations and influx of Betula, Juniperus and Salix together with macrofossil leaves indicate shrub growth around the site during the initial phases of vegetation colonisation. Unstable conditions followed ca. 10 380 cal. yr BP that changed both the upland vegetation and the aquatic plant communities. A decrease in percentage values of shrub pollen is recorded, with replacement of both aquatics and herbaceous plants by pioneer plant communities. An increase in total pollen accumulation rates not seen in the concentration data suggests increased sediment delivery. The catchment changes are consistent with less seasonal, moister conditions. Subsequent climatic amelioration reinitiated a warmth‐driven succession and catchment stabilisation, but retained high precipitation levels influencing the composition of the post‐event communities. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

17.
Full‐glacial pollen assemblages from four radiocarbon‐dated interstadial deposits in southwestern Ohio and southeastern Indiana imply the presence of herbaceous vegetation (tundra or muskeg with subarctic indicator Selaginella selaginoides) on the southern margin of the Miami lobe of the Laurentide Ice Sheet ca. 20 000 14C yr BP. Scattered Picea (spruce) and possibly Pinus (pine) may have developed regionally ca. 19 000 14C yr BP, and ca. 18 000 14C yr BP, respectively. Spruce stumps in growth position support a local source of pollen. Prior to the ca. 14 000 14C yr BP glacial advance, small amounts of Quercus (oak) and other deciduous pollen suggest development of regional boreal (conifer–hardwood) forests. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

18.
Stratigraphic analyses of peat composition, LOI, pollen, spores, macrofossils, charcoal and AMS ages are used to reconstruct the peatland. vegetation and climatic dynamics in the Pur-Taz region of western Siberia over 5000 years (9300-4500 BP). Section stratigraphy shows many changes from shallow lake sediment to different combinations of forestcd or open sedge, moss, and Equisetum fen and peatland environments. Macrofossil and pollen data indicate that Larix sibirica and Beth pubescens trees were the first to arrive, followed by Picea obovata . The dominance of Picea macrofossils 6000-5000 BP in the Pur-Taz peatland along with regional Picea pollen maxima indicate warmer conditions and movement of the spruce treeline northward at this time. The decline of pollen and macrofossils from all of these tree species in uppermost peats suggests a change in the environment less favorable for their growth, perhaps cooler tempratures and/or less moisture. Of major significance is the evidence for old ages of the uppermost peats in this area of Siberia, suggesting a real lack of peat accumulation in recent millennia or recent oxidation of uppermost peat.  相似文献   

19.
Pollen and plant macrofossil analyses from Svanåvatnet in northern Norway provide records of past vegetation and climate in this region from c . 8700 cal. yr BP until the present. Pollen accumulation rates and the presence of plant macrofossils indicate that Betula pubescens (birch) was present from c . 8600 cal. yr BP and Pinus sylvestris (pine) from c . 8200 cal. yr BP. Quantitative climate is reconstructed using modern pollen-climate transfer functions based on weighted-averaging partial least squares regression. A rapid increase in mean July temperature (Tjul) and mean annual precipitation (Pann) is inferred for the early Holocene. At times when tree abundance is at its highest and most diverse, inferred Tjul indicates maximum temperatures during the mid-Holocene of about 2°C warmer than at present. During the same time period, inferred Pann is 200–300 mm above present-day conditions until c . 3000 cal. yr BP. Mean January temperatures (Tjan) are reconstructed to be about 2°C warmer than today from 8000 to 3500 cal. yr BP. After 3500 cal. yr BP until today, a gradual decrease is seen in all the reconstructed climate parameters, together with a reduction in tree abundance and the development of a mosaic of open vegetation with grasses, dwarf shrubs and wet areas, and of woodland containing B. pubescens , P. sylvestris and Picea abies (spruce).  相似文献   

20.
Pollen accumulation rates (PARs) provide a potential proxy for quantitative tree volume (m3 ha?1) reconstruction with reliable absolute pollen productivity estimates (APPEs). We obtained APPEs for pine, spruce and birch at their range limits in northern Finland under two temperature periods (‘warm’ and ‘cold’) based on long‐term pollen trap and tree volume records within a 14‐km radius of each trap. APPEs (mean ± SE; × 108 grains m?3 a?1) tend to be higher for the ‘warm’ periods (pine 123.8 ± 24.4, birch 528.0 ± 398.4, spruce 434.3 ± 113.7) compared with the ‘cold’ periods (pine 95.5 ± 37.3, birch 317.3 ± 282.6, spruce 119.6 ± 37.6), although the difference is only significant for spruce. Using an independent temperature record and the APPEs obtained, we reconstruct a low‐frequency record of pine volume changes over the last 1000 years at Palomaa mire, where a high‐resolution record of Pinus PARs is available. Five phases are distinguished in the reconstruction: moderate pine volume, AD 1080–1170; high volume, AD 1170–1340; low volume, AD 1340–1630; very low volume, AD 1630–1810; and rising pine volume, AD 1810–1950. These phases do not coincide with periods of high or low June–July–August temperatures, and thus appear to reflect regional variations in tree volume, while high‐frequency changes within each time‐period block show variations in PARs in response to temperature. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

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