Ancient Forest Research Report No. 4
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A 10,000-YEAR VEGETATION HISTORY OF THE TEMAGAMI REGION OF ONTARIO WITH SPECIAL EMPHASIS ON WHITE PINE
by
Roland I. Hall
Katharine E. Duff
and
Peter A. Quinby
1994
ACKNOWLEDGEMENTS
This research was supported by the Temagami Wilderness Society. We thank I.R. Walker for valuable field assistance, Katherine Bidwell for her editorail comments and Sudbury Aviation for air transport. Dr. J. Terasmae and H. Melville provided radiocarbon dating.
INTRODUCTION
Historical records indicate that white pine (Pinus strobus L.) was once significantly more abundant in the northern Great Lakes region than it is today (Terasmae and Anderson 1970, Jacobson 1979, Ritchie 1987, Liu 1990). The large size, straight bole, and high fibre content make white pine an economically valuable and much sought after timber commodity (Ritchie 1987). The intensive logging practices of the recent past have caused a significant reduction of old-growth white pine forests in Ontario (Hodgins and Benedickson 1989). Logging practices are now being evaluated and scrutinized, as the existence of significant areas of old-growth pine forests is threatened.
Considerable controversy exists concerning the ecological principles guiding current forest management of white pine in Ontario. Present practices are based on the theory that periodic catastrophic fire results in even-aged white pine stands, and is essential for white pine regeneration and proliferation (Maissurow 1935), and that, in the absence of periodic catastrophic disturbance, these "over-mature" pine forests will degenerate, resulting in the waste of fibre. Even-aged forest management including clearcutting is considered an ecologically sound approach to logging by current Ontario forest managers who contend that it best mimics the action of catastrophic wildfire (Steill 1985, Ontario Ministry of Natural Resources 1989).
Some researchers have found, however, that old-growth white pine forests can possess an uneven age structure as a result of non-catastrophic, local disturbances (Gilbert 1978, Holla and Knowles 1988, Quinby 1991). For example, inventories of live and dead vegetation in the Temagami region of central Ontario indicate that old-growth white pine communities have been self-replacing over at least the past 700 years (Quinby 1989, 1991). The uneven age structure and dominance of white pine over this period has been maintained by continuous recruitment of the species. Thus, a silvicultural system such as selection logging that maintains the uneven age structure of white pine stands would, in some instances, more accurately reflect the silvics of white pine than do the even-aged logging techniques which are presently being applied.
An historical perspective gained by paleoecological methods may provide additional insight into the long-term dynamics of forest composition within Temagami's northern temperate forested landscape. Past forest vegetation composition can be reconstructed from the pollen record preserved in lake sediments and peat deposits (Bryant 1978, Birks 1981), and charcoal remains can be used to estimate past fire regimes (Winkler 1985). The onset, rate and magnitude of past changes in forest communities can be assessed, and the processes responsible for these changes may be inferred. In the Temagami region, paleoecological methods may be the only source of information on the nature of prehistorical forest communities.
The purpose of this study was (1) to gain additional insight into the long-term forest community dynamics within the Temagami landscape and (2) to focus on the history of the Temagami white pine population by documenting its arrival and expansion in the area and by investigating the role of large-scale catastrophic wildfire as an influence on its population dynamics. Paleoecological techniques were used to reconstruct the Holocene vegetation and fire history in the Temagami region which presently supports one of the most significant concentrations of old-growth white pine forest in the world (Quinby and Giroux 1993).
SITE DESCRIPTION
A sediment core was taken from a small lake (Lake 306) on the northeast edge of the Obabika Lake Pine Stand - the world's largest known stand of old-growth white pine forest (Quinby 1993). The lake is located at longitude 47o09'N, Latitude 80o17'W, in the southeast corner of Shelburne Township, District of Sudbury (Figure 1). The lake occupies a small (8 ha), shallow (maximum depth located = 3m) basin adjacent to a fault line, at an elevation of 306 m. The catchment area is small and limited to the immediate area surrounding the lake. A steep 60 m granite cliff of the fault line flanks the east edge of the lake. The remainder of the lake is surrounded by low lying boggy areas. Bog development is especially advanced along the west edge. A small stream flows into the lake at the northwest corner from Bob Lake (0.5 km to the north). A small outflow occurs at the south end that eventually flows into Obabika Lake (3.4 km to the south).
METHODS
Sediment Core
In paleoecological studies, small lake basins are sampled in order to minimize the contribution of regional or non-local pollen to the statigraphic sequence caused by long-range wind transport (Jacobson and Bradshaw 1981, Jackson 1990). For example, to study the history of a 1 km2 old-growth pine forest in northwestern Minnesota, Clark (1990) sampled sediments from lakes of 5.4, 3.0 and 2.4 ha. Thus, in order to maximize the sampling of locally derived pollen for this study, a small 8 ha lake ("Lake 306") was chosen. Even so, the majority (approx. 75%) of pine pollen preserved in the sediments of "Lake 306" probably originated from within a 47 km radius (Jackson 1990), and charcoal particles may originate from an even greater distance (Clark 1988). Therefore, the pollen data from this study can only be applied to the Temagami region as a whole, and forest community responses within the region may vary locally.
The sediment of the lake was sampled on April 7, 1990 with an 880 cm long modified Livingston piston corer with a 3.5 cm diameter (Vallentyne 1955). The sediment core was taken through ice cover, from the south end of the lake, at a water depth of 3 m. The core was extruded horizontally and split in half longitudinally upon return to the lab. One half was stored intact in PVC holders. The other half was sectioned into 1 cm intervals, and used for pollen and charcoal analysis and radiocarbon dating.
The surficial lake sediments have a high water content, which makes sectioning of the top portion of the Livingstone sediment core difficult. Therefore, a 38 cm surface core was retrieved from a separate, adjacent site using a modified Kajak-Brinkhurst (K-B) corer (Brinkhurst et al. 1969). The core was sectioned vertically in the field, immediately following retrieval. It was sectioned at close intervals (0.25 cm intervals from 0-5 cm, 0.5 cm intervals from 5-10 cm, 1 cm intervals from 10-38 cm) using a portable extruding device (Glew 1988). This core was used for pollen and charcoal analysis of the uppermost sediments.
Dating
Radiocarbon (14C) dating was performed by the Brock University Geological
FIGURE 1 - Location of "Lake 306" (A: Temagami region surrounding "Lake 306" and its location in Ontario; B: "Lake 306" and its estimated catchment - marked by hatched area)
Sciences Radiocarbon Lab (Brock University, St. Catherines, Ontario). Wet sediment was submitted from 6 intervals (10-20 cm thick) in the core. The samples were not pretreated (i.e. no removal of foreign material or humic acids, acid leach or distilled water wash). Sample dry weights ranged from 10.2-35 g, which is sufficient for radiocarbon age determination (Terasmae 1984).
Pollen Analysis
Pollen slides were prepared for qualitative analysis from wet sediment using a modification of the standard Faegri and Iverson (1975) technique. Our method omitted the hydrofluoric acid treatment. A total of 45 samples were taken at a minimum distance of every 30 cm along the length of the core, and more frequently (every 5 or 10 cm) in regions where the pollen assemblage showed marked changes. This provided a mean temporal resolution of approximately 217 years between samples. A minimum of 400 pollen grains were counted at each stratigraphic level. Pollen abundance was expressed as a percentage of the sum of all pollen grains originating from terrestrial vegetation.
Pollen taxonomy was based on a modern reference collection at the Department of Biology, Queen's University, and published keys (Kapp 1969, McAndrews et al. 1973, McAndrews and King 1976). White pine pollen grains can be differentiated from other pine species in eastern North America - it is the only haploxylon pine species in the Temagami region, and its pollen grains characteristically possess distal verrucae (or "belly warts", McAndrews et al. 1973). Jack pine (Pinus banksiana Lamb.) and red pine (Pinus resinosa Ait.) are diploxylon species and lack distal verrucae. Pollen grains from jack pine and red pine cannot be reliably distinguished and were grouped together.
It should be noted that because pine trees produce prodigious amounts of widely dispersed pollen (Birks and Birks 1980), pine populations are typically overrepresented by sedimentary pollen profiles. Hence, the percent contribution of pine trees to a given forest community is less than that indicated by the sedimentary record. At present, there are no methods available to estimate actual numbers of trees from the relative abundance of pollen in lake sediments. Therefore, the pollen data from this study should not be directly translated into percent values of the forest composition, but should be used to indicate relative changes in the abundances of the various taxa.
Charcoal Analysis
Charcoal carbon was measured using the chemical assay technique of Winkler (1985). Sediment samples (ca. 1 g wet weight) were dried overnight at <100C, cooled in a dessicator, and weighed (DW). The samples were digested in 5 ml of nitric acid in a boiling water bath to remove organic material, carbonates and pyrite. After digestion was complete (ca. 1.5 hours), the samples were rinsed three times with distilled water, dried overnight at <100C, cooled in a dessicator and weighed (NW). The samples were then ignited at 600C for 3 hours, cooled in a dessicator and weighed (IW). Charcoal, expressed as a percentage of sediment dry weight, was calculated according to the following formula:
Charcoal was determined for 48 samples, from core intervals identical or close to those analyzed for pollen. Replicate runs (n=3) were performed at 12 depths to estimate error.
Statistical Analysis
Principal components analysis (PCA) was used to identify patterns in the species data from the post-glacial history of "Lake 306". The species data (expressed as percentages of the total pollen sum) were first square-root transformed to equalize variances. This step is necessary because the pollen assemblage is dominated throughout the core by a few species (i.e. white pine, jack pine/red pine, birch species (Betula spp.)). Rare taxa (<1% at all depths in the core), and taxa that could not be reliably distinguished, were excluded from the analysis.
PCA explains the variance in species-sample data by fitting a straight line through a multidimensional normal curve, such that the residual sum of squares is minimized (Jongman et al. 1987). This line is the first ordination axis. Further axes are constructed in the same way, with the constraint that they are uncorrelated. The eigenvalue (lambda) of each axis is a measure of the percentage of variance in the species-sample data that is explained by that axis. The correlation between any two points on the ordination diagram can be estimated by the angle subtended by those two points and the origin. Changes in the community composition over time can be followed by plotting the trajectory of the samples (depths).
RESULTS
The sediment core from "Lake 306" consisted of a 760 cm sequence of dark brown organic gyttja overlying a 120 cm sequence containing layers of laminated clays (possessing blue and white clay bands, or rhythmites) and layers of a pink sand. Layers of clay and sand are typically found at the bottom of sediment cores from lakes in northern North America. These basal layers of "glacial flour" were deposited as the glaciers receded and generally represent the early postglacial period. The presence of basal clay and sand indicates the entire Holocene record is contained within the sediment core retrieved from "Lake 306". Pollen grains were rare or absent in the basal clay and sand layers. Several factors could account for this. Vegetation cover, and hence pollen production were extremely low at this time due to the cold climatic conditions and lack of soils. Also, pollen was likely diluted by the relatively rapid deposition of the postglacial clays and sands.
Radiocarbon dates with their associated error values are shown in Figure 2. The organic sequence of the core includes the last 9,750 ± 230 radiocarbon years; this value agrees well with previously published values for lakes in this region (Terasmae 1968, Vincent 1973, Liu 1990). Radiocarbon dates associated with changes in the pollen stratigraphies also correspond closely to those published previously (see below), with the exception of the most recent radiocarbon date (1,240 ± 90 BP). We believe that the most recent radiocarbon date is inaccurate and overestimates the true age of this sediment for two reasons.
First, the most recent radiocarbon date suggests that sedimentation rates
have declined in the last 1,000 years. The earlier dates indicate an apparent
sedimentation rate of ca. 8 cm/century, but the most recent date indicates an
apparent sedimentation rate of only 2 cm/century in the uppermost 40 cm of the
FIGURE 2 - Pollen percentage diagram for "Lake 306", Temagami, Ontario (14C
dates provided by Brock University Geological Sciences Radiocarbon Laboratory,
St. Catherines, Ontario; charcoal expressed as percent of sediment dry weight;
horizontal lines indicate range of 4 replicate samples around mean value (closed
square))
core. However, Smol (1981) has observed that sedimentation rates usually appear to increase, not decrease, in recent lake sediments. This occurs because the water content is higher in more recent sediments than in older, more compacted sediments. Second, Ambrosia pollen increased in relative abundance at a sediment depth of 10 cm. This event can be reliably attributed to the arrival of European settlers, and subsequent land clearing, which occurred ca. 150 years ago (Bassett and Terasmae 1962). It is therefore unlikely that the core interval 10-40 cm represents 1,100 years of deposition. Based on these two lines of evidence, we believe a more reliable date for the core interval 30-40 cm is 450 BP. The discrepancy between the radiocarbon date and our inferred date is most likely due to contamination of the sediment sample by material of an older radiocarbon age (Terasmae 1984). We suspect that coal particles from the nearby smelters in Sudbury, Ontario may have contaminated the recent sediments of "Lake 306".
PCA analysis was used to track changes in the pollen stratigraphies. The first two axes of the PCA analysis explain 78% of the variance in the species-sample data, with 60% accounted for by the first axis alone (Figure 3). The
core samples are predominantly dispersed along the first axis. White pine and jack pine/red pine are more highly correlated to axis 1 than any other taxa, indicating that changes between core samples are largely defined by changes in these taxa. The stratigraphic sequence of pollen assemblages was divided into 5 zones based on the spatial proximity of samples (noted as depths in Figure 3) on the PCA ordination diagram.
Zone 1 (745 - 695 cm; ca. 9,750-8,890 BP) is characterized by a predominance of spruce (Picea mariana (Mill.) B.S.P. and P. glauca (Moench) Voss) pollen (50% relative abundance) (Figure 2). This spruce zone characteristically develops during the early post-glacial period (approximately 9,500 BP) in the northern Great Lakes region (Terasmae 1968). Jack pine/red pine (25%) and birch spp. (20%) were common components of the vegetation and tamarack (Larix laricina (Du Roi) K. Koch) attained maximum representation (5%) during this period. Pioneer herbs and shrubs (Artemisia, Salix, and Ambrosia) were relatively common (approximately 2%) and thermophilous taxa (oak (Quercus rubra L.), elm (Ulmus americana L.)) were present at low but constant percentages. Pollen abundance was low throughout zone 1.
Zone 2 (680 - 575 cm; ca. 8,890-7,200 BP) is characterized by a period of dramatic change in the forest community (Figure 2). The relative abundance of jack pine/red pine increased sharply while the spruce pollen declined. Jack pine/red pine reached maximum abundance (68%) in this zone. Balsam fir (Abies balsamea (L) Mill.), speckled alder (Alnus rugosa (Du Roi) Spreng) and birch (Betula papyrifera Marsh. and B. lutea Michx. f.) all had coincident peaks in their relative abundances within this zone.
Zone 3 (550 - 515 cm; ca. 7,200-6,260 BP) is characterized by the arrival and sharp increase in the relative abundance of white pine pollen (Figure 2). Beech (Fagus grandifolia Ehrh.), eastern hemlock (Tsuga canadensis (L.) Carr.), and maple (Acer rubrum L. and A. saccharum Marsh.) pollen appear at the bottom of this zone at low levels and may indicate the arrival of small populations in the vicinity of "Lake 306". Spruce and birch pollen declined. White pine pollen attained a relative abundance of 30% in this zone, and maintained or exceeded this value throughout the remainder of the post-glacial period, until the most recent period (ca. 450 BP).
Zone 4 (505 - 20 cm; ca. 6,260-250 BP) reflects a condition of relative
FIGURE 3 - Principal components analysis of "Lake 306" pollen assemblages
(Numbers refer to sediment depth in centimeters. Taxon codes are; ABI = Abies,
ACE = Acer, ALN = Alnus, AMB = Ambrosia, ART = Artemisia, BET = Betula, FAG =
Fagus, LAR = Larix, PBR = Pinus banksiana/resinosa, PIC = Picea, PIN =
undifferentiated Pinus, POA = Poaceae, PST = Pinus strobus, QUE = Quercus. SAL
= Salix, TSU = Tsuga, and ULM = Ulmus)
homeostasis in the pollen assemblage (Figure 2). White pine is the dominant tree taxa throughout this period, though it declined slightly in the upper half of the zone. Birch, jack pine/red pine and spruce were subdominant components of the forest. Alder, oak, elm, beech and maple were present at low, but constant abundances throughout this period. White pine and birch pollen increased slightly in relative abundance in the lower half of zone 4. Spruce and jack pine/red pine pollen, in contrast, declined slightly in the middle of this period and increased near the end. Balsam fir and tamarack also showed a slight increase in relative abundance at the end of this period.
Zone 5 (15 - 0 cm; ca. 200 BP - present) encompasses the period of European settlement and activity in the region surrounding "Lake 306" (Figure 2). The increase in pioneering shrub taxa (Ambrosia and Artemisia) beginning at 10 cm indicates land clearing activities of European immigrants, probably about 150 years ago (Bassett and Terasmae 1962). Hardwood taxa (birch, alder, oak and maple) increased in relative abundance during this period, while softwoods (white pine and spruce) generally decreased. The relative abundance of white pine undergoes the most dramatic decline of all tree taxa. White pine values are reduced nearly three-fold during this period (from 26% to 9%).
Charcoal values in the early post-glacial history (pre-9,750 BP) of "Lake 306" were lower than at any other time (mean % charcoal = 1.2%), and probably represent non-local charcoal deposition given the relatively low density of woody taxa during this early period (Figure 2). Percent charcoal rose steadily through zones 1 and 2, as arboreal vegetation was established in the lake's catchment. Charcoal values remained relatively constant (ca. 5%) in zones 3 and 4. Charcoal concentrations in the most surficial sediments could not be determined accurately. The water content of the surface sediment was very high, and an insufficient quantity of dried sediment was available for analysis. The difference in dry weight before and after ignition was often greater than the precision error (±0.002g) of the weighing scales. Hence, the range of charcoal values obtained from the 4 replicate samples was very large (2.9-10.0%). Also, this technique tends to give unreliable estimates of fire in recent sediments, due to contamination by anthropogenic fossil fuel combustion (Winkler, 1985). Therefore, we have excluded zone 5 charcoal data from the discussion.
DISCUSSION
Following glacial recession 11,000 - 10,100 BP (Saarnisto 1974), a spruce dominated boreal forest expanded southward into the Temagami region. This forest became established at least as early as 9,750 BP and lasted until about 8,900 BP. The large size of the spruce pollen grains, as well as macrofossil and pollen evidence from nearby Nina Lake (Lui 1990) suggests that this forest was comprised mainly of white spruce (Picea glauca). Low concentrations of pollen and the occurrence of relatively high percentages of pioneer herbs and shrubs (Artemisia, Salix, and Ambrosia) indicate an open, patchy forest condition. The boreal forest at that time, however, was unlike the boreal forests of today, as shown by the relatively high percentages of the thermophilous taxa oak and birch in the historical boreal forest (Lui 1990). The lack of a modern analogue is likely due to a combination of unique climatic and edaphic conditions.
The major climatic influence relates to the ice front situated approximately 100 km to the north of the Temagami region which created anticyclonic winds resulting in a periglacial climate with milder and drier winters and cooler and windier summers relative to modern boreal forests (Amundson and Wright 1979). Also, growth of thermophilous hardwoods would be favoured on newly formed glacial tills and base-rich soils (Lui 1990). Jack pine/red pine was likely overrepresented due to the combination of low pollen production from local vegetation and the relatively large source area for pine pollen which resulted in its high relative abundance values (Jackson 1990).
Thus, the initial vegetation cover of the Temagami region following glacial retreat 10,000 years ago most likely consisted of a patchy, open boreal forest with white spruce and tamarack occupying low-lying, moist and ombrotrophic areas, oak and birch occurring on glacial tills, and pioneering herbs and shrubs sparsely distributed between tree patches. The patchy distribution of the forest probably contributed to a low incidence of fire, as indicated by the charcoal data obtained in this study.
A closed boreal forest dominated by pine along with spruce, birch (probably white birch, Lui 1990) and alder developed about 8,900 BP. The small size of the pine pollen suggests that the increase in jack pine/red pine was due to an increase in jack pine as opposed to red pine. Macrofossil evidence from nearby Nina Lake (Liu 1990) supports this view. The replacement of white spruce by jack pine is believed to have occurred in response to warmer climatic conditions (Terasmae 1968, Vincent 1973, Liu 1990). The composition of this historical boreal forest closely resembles the boreal forest presently located to the north of the Temagami region. The development of the closed forest canopy coincided with an increase in % charcoal, suggesting a rise in the frequency and/or magnitude of fire events with the increase in fuel. The charcoal content remained relatively constant thereafter, despite subsequent changes in forest species composition.
At 7,200 BP the boreal forest was succeeded by a Great Lakes-St. Lawrence forest dominated by white pine which has occupied the region since. The immigration and establishment of white pine coincided with declines in spruce and birch. The pollen data for jack pine/red pine show no distinct trend. However, macrofossil evidence from nearby Nina Lake (Lui 1990) suggests that the relative abundance of red pine increased at the expense of jack pine during this period. Eastern hemlock, beech and maple pollen occurred consistently at low relative abundances throughout zone 3, but at levels sufficient to indicate their presence locally (Davis et al. 1986). The arrival and expansion of white pine, red pine, eastern hemlock, beech, and maple reflects the northward expansion of the Great Lakes-St. Lawrence ecotone boundary during the Hypsithermal period of climatic warming (7,400 - 4,000 BP) which was displaced at least 140 km north of its present position (Terasmae and Anderson 1970, Liu 1990).
The last 7,200 years, with the exception of the past approximately 450 years, encompassed the period of greatest stability within the forest community of the Temagami region. During this period, the region was covered by a forest dominated by white pine with red pine, spruce and birch present as sub-dominant components of the community. Alder, oak, elm, beech and maple were common, but less abundant. Gross changes in forest composition did not occur in zone 4, rather individual taxa responded gradually to natural influences, over long time periods. For example, white pine and birch increased slightly around 6,000 BP and white pine attained a maximum relative abundance (45%) at the peak of the Hypsithermal, approximately 4,000 years ago. The period of Neoglacial cooling following the Hypsithermal caused an increase in taxa that are more commonly found in boreal forests including spruce, jack pine, tamarack, and balsam fir while white pine abundance decreased. The forest community of zone 4 is similar to the present day forest (zone 5), except that white pine is presently much less abundant and pioneering herbs and shrubs are more abundant.
The past 450 years have been a period of rapid change in the forest community of the Temagami region. This is especially apparent in the white pine population, which showed a sharp and substantial decline. Two factors may account for the observed white pine decline. First, it may have occurred in response to the cooling trend between ca. 400 BP and 150 BP known as the Little Ice Age (Gribbin and Lamb 1978), but the evidence for this is unclear. For example, the white pine decline was not accompanied by a simultaneous increase in spruce, as might be expected. Also, cooler temperatures during the Neoglacial (ca. 4,000-450 BP) did not produce a similar sharp decline in white pine pollen in "Lake 306" or nearby lakes (Liu 1990). Unfortunately, detailed information regarding the relative rates and magnitudes of temperature change during these two periods is not available, thus, the effect of climatic cooling on the local white pine population cannot be assessed.
Second, the vegetation of the Temagami region has been greatly altered by human activities including intense forest clearing for farming, mining, and logging purposes over the past 180 years (Hodgins and Benedickson 1989). These changes are reflected by a coincident rise in Ambrosia and birch pollen both of which are pioneer taxa that colonize following disturbance. A similar decline in white pine pollen at nearby Nina Lake during the same period was identified by Liu (1990) who, with reference to Huhn (1974), attributed this decline, at least in part, to human activities such as the mining and smelting industries in the Sudbury area. Due to the lack of fine-scale temporal and spatial resolution of the techniques used for this study, it was not possible to establish the cause of recent forest compositional changes in the Temagami region. It is most likely that both climatic and anthropogenic mechanisms have played a role in these changes.
Given the fact that (1) the majority of the pollen data in this study are representative of a 700,000 ha area and (2) the mean temporal resolution of the samples is 217 years, it is not possible to address the role of fire which may have burned an area of 10,000 ha every 50 to 100 years (Cwynar 1977, 1978, Terasmae and Weeks 1979). It was, therefore, not possible to confirm or reject the non-catastrophic theory of forest regeneration (Quinby 1991). However, in the context of the spatial and temporal resolution represented in this study, the results indicate that (1) there were no periodic fluctuations in the white pine population between its arrival 7,200 BP to recent centuries, (2) with the exeption of the last 450 years, white pine comprised approximately one-third of the pollen sum of the forest vegetation in the Temagami region and (3) white pine has decreased in abundance over the last 450 years in the Temagami region.
In order to address more specifically the theory of non-catastrophic white pine forest regeneration (Quinby 1991) using historical ecological studies, the combination of two approaches may prove useful. The first step requires establishing a relationship between tree fire-scar data and stratigraphic charcoal data to estimate the amount of charcoal that indicates local fire (Clark 1990). The reconstruction of historical fire could then be combined with local pollen data. To isolate local pollen from regional pollen, sediments from small paired basins that are close together and that are characterized by different soil types that commonly support different vegetation types (ideally one dominated by white pine and one not dominated by white pine) could be sampled. Differences in pollen diagrams would be evidence of local differences in vegetation composition (Jacobson 1979) which could then be compared to differences in local fire history.
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