A record of Lateglacial and Holocene vegetation and climate change from Woods Lake, Seymour Inlet, coastal British Columbia, Canada (original) (raw)
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Journal of Paleolimnology, 2002
A stratigraphic record from a lake in the Central Plateau Regionof northern British Columbia reveals changes in environment and inferredclimate during the Holocene. Upon deglaciation (ca. 11500 BP), Skinny Lakebecame an embayment of an ice-dammed lake. High clastic sedimentationrates, an unstable landscape, and cool, possibly wet conditions likelypersisted until the early Holocene (ca. 9000 BP). From ca. 9000–8300 BPdeclining lake levels coupled with warm and dry conditions resulted in theformation of a prominent marl bed. A colonizing shrub and herb assemblagepersisted from 9000 BP until about 8300 BP when it was replaced by a spruce(Picea) and subalpine fir (Abieslasiocarpa) forest under slightly cooler and moister conditions. Themiddle Holocene was warmer-than-present, however, decreasingtemperature and increasing precipitation trends characterize the period fromca. 6000 BP–3000 BP. The transition to modern climate at 3000 BP isevident primarily in the lithostratigraphic record and corresponds with theinitiation of the Tiedemann glacial advance (ca. 3300 BP) in thesouth-coastal mountains of British Columbia. A significant change infossil pollen occurs at ca. 2400 BP and is characterised by an increase in pinepollen accompanied by decreases in alder (Alnus), spruceand fir. This also coincides with an increase in west-sourced exoticwestern hemlock (Tsuga heterophylla) and cedar type(Cupressaceae) pollen possibly transported by regional changes in air masscirculation patterns associated with Aleutian Low dynamics. This studydemonstrates that both lithostratigraphic and biotic proxies are helpful inreconstructing the timing and nature of climate change and that each may havevarying sensitivities to a particular type of change.
Journal of Quaternary Science, 2009
A pollen-based study from Tiny Lake in the Seymour-Belize Inlet Complex of central coastal British Columbia, Canada, permits an evaluation of the dynamic response of coastal temperate rainforests to postglacial climate change. Open Pinus parklands grew at the site during the early Lateglacial when the climate was cool and dry, but more humid conditions in the later phases of the Lateglacial permitted mesophytic conifers to colonise the region. Early Holocene conditions were warmer than present and a successional mosaic of Tsuga heterophylla and Alnus occurred at Tiny Lake. Climate cooling and moistening at 8740 AE 70 14 C a BP initiated the development of closed, late successional T. heterophylla-Cupressaceae forests, which achieved modern character after 6860 AE 50 14 C a BP, when a temperate and very wet climate became established. The onset of early Holocene climate cooling and moistening at Tiny Lake may have preceded change at more southern locations, including within the Seymour-Belize Inlet Complex, on a meso-to synoptic scale. This would suggest that an early Holocene intensification of the Aleutian Low pressure system was an important influence on forest dynamics in the Seymour-Belize Inlet Complex and that the study region was located near the southern extent of immediate influence of this semi-permanent air mass. Pollen diagram of the relative abundance of select pollen taxa. Lithology, percent loss-on-ignition and chronology of the Tiny Lake sediment core are included
Marine Geology, 2001
High-resolution pollen analysis of laminated marine sediments from ODP Hole 1034B in Saanich Inlet, British Columbia reveals changes in vegetation and inferred climate during the Holocene. Four main pollen zones are discerned using constrained cluster analysis. Although the timing of major vegetation changes at the Saanich Inlet is similar to other study sites in the Paci®c Northwest, the composition of pollen assemblage zones is different from the mainland sites. Vegetation assemblages reconstructed from the pollen and spore record include a Douglas-®r (Pseudotsuga menziesii) parkland with abundant grass (Poaceae) and bracken (Pteridium) between 11,450 and 8300 BP (all ages are calibrated calendar years), oak (Quercus) savanna or parkland with high grass and bracken (8300±7040 BP), a mixed deciduous/coniferous forest with oak, western hemlock (Tsuga heterophylla) and Douglas-®r (7040±5750 BP), and the development of modern coastal temperate forest with the marked expansion of cedar (Cupressaceae), western hemlock, spruce (Picea) and Douglas-®r (5750±1050 BP). Climatic periods inferred from the cores include an early Holocene warm/dry interval (11,450±8300 BP), a warm period with mild winters (8300±7040 BP), a period of transitional mid-Holocene climate (7040±5750 BP), and the advent of a relatively cool/ wet neoglacial climate after 5750 BP. Modern conifer forests and oak savannas became established by about 3800 BP. The Saanich Inlet pollen record indicates that vegetation and inferred climate change was particularly rapid between 8700 and 8300 BP when grass and bracken abruptly decrease and oak becomes a signi®cant component of the paleovegetation. Because neoglacial conditions have prevailed from 3800 years to present in the Paci®c Northwest, factors other than climate, such as anthropogenic modi®cation of the landscape, may be responsible for the persistence of oak savannas. q
Arctic, Antarctic, and Alpine Research, 2000
Multiproxy paleoecological investigation of a small lake in the high subalpine zone near Stoyoma Mountain, northern Cascade Mountains of British Columbia, reveals significant change in vegetation, limnic conditions, and inferred climate throughout the Holocene (last 10,000 radiocarbon years). Three zones of distinct pollen, plant macrofossil, and chironomid assemblages are apparent in the sediment core from 3M Pond (informal name). A dry, sparsely vegetated spruce parkland and a wann adapted chironomid community existed in and around the study sites in the early Holocene (ca. 10,000 to 7000 '4C yr HP). Between 7000 and 3500 '4C yr BP, Engelmann spruce-subalpine fir forest conditions established and then declined around 3M Pond leading to modem subalpine parkland conditions from 3500 '4C yr HP to present. Chironomid communities at 3M Pond between 7000 and 3500 4C yr HP are indicative of warmer waters than present, but show a transition to modem assemblages. Three climatic regimes are identified near Stoyoma Mountain:
Palaeogeography, Palaeoclimatology, Palaeoecology, 2002
Pollen, charcoal, and plant macrofossil analyses reveal five postglacial vegetation periods at Crater Lake, Crater Mountain, British Columbia. The first period, beginning ca. 11 400 14 C yr BP was characterized by Artemisia steppetundra. At 9700 14 C yr BP, Pinus parkland developed, and by 6700 14 C yr BP was replaced by fire-successional Pinusdominated Engelmann spruce and subalpine fir forest (ESSF). At 3800 14 C yr BP, Picea became a more important element of the forest, and modern forest structure and composition developed by 1600 14 C yr BP. Comparison of the fossil vegetation and fossil midge data derived from several ESSF sites in the southern interior reveals (1) similar late-Pleistocene vegetation and climate at all sites, (2) three distinct Holocene climatic stages: warm/dry, warm/moist, and cool/moist, (3) confirmation of the warm/moist period as a distinct climatic period, and (4) distinct differences in Holocene vegetation change among the sites. The driest and warmest site was most sensitive to climatic change, whereas cooler, moister sites were less sensitive. The present east^west climate gradient originated with postglacial warming at the beginning of the Holocene. Vegetation response to climate change and natural disturbance in these sites is strongly controlled by local site characteristics. These characteristics may have implications for forest, environment, and resource management.
Géographie physique et Quaternaire, 2000
Environmental sensitivity to temperature change was established by comparing pollen, plant macrofossils, macroscopic charcoal, and sediment yield data from Lake of the Woods, Cathedral Provincial Park in the Cascade Mountains of southern British Columbia, Canada, to an independent record of midge-inferred paleotemperature. Steppe vegetation with some spruce and fir occurred initially, developing into pine forests in the warm early Holocene. These forests burned often, preventing spruce and fir succession. Once established, the forests retained an Engelmann Spruce-Subalpine Fir character. After 8000 cal BP, in warm but wetter conditions, the forest contained less pine and fires burned less frequently. About 4000 cal BP, cooler temperatures resulted in closure of the Engelmann Spruce-Subalpine Fir forests and a further reduction in fire frequency. Sediment yield results suggest a stable environment throughout the Holocene, likely due to sediment trapping in two upstream lakes. Midge-i...
The Arcellacean (Thecamoebian) fauna was assessed in five Holocene sediment cores obtained from James and Granite lakes in the Temagami region of northeastern Ontario. In addition, palynological analysis was carried out on two of these cores, one each from James and Granite lakes. The first indication of postglacial colonization by plants was the appearance of rare Cupressaceae pollen, dated to 10,800 yr BP. Plant diversity began to increase by 10,770 yr BP when Pinus spp. and Larix migrated into the area. The first appearance of arcellaceans occurred after 9650 yr BP in assemblages dominated by Centropyxis constricta and opportunistic Centropyxis aculeata. High abundances of charophytes in the cores until 8800 yr BP indicated that macroalgae were proliferating at this time. This deposition is interpreted to have occurred during the draining of an ice-marginal lake following the retreat of the Laurentide Ice Sheet. Based on pollen analysis, warmer conditions associated with the Holocene Hypsithermal prevailed in the area from 6250 to 4115 yr BP. The stable, open Great Lakes -St. Lawrence type forest that developed here at the beginning of the Hypsithermal continues to prevail to the present. The periodic colonization of the lake by beavers (Castor canadensis) acted as a control on water-level and eutrophication through the Holocene. Evidence of eutrophication was indicated in the core samples by the abundance of high levels of the alga Pediastrum and the arcellacean Cucurbitella tricuspis. Eutrophication periodically developed when beavers dammed a site, causing the rate of flow in drainage streams to slow and stagnant conditions occurred. When the site became depleted of the nearby trees, which were preferred by beaver (Betula, Alnus and Populus), the dam would be abandoned, causing the water-level to drop. Stagnant conditions were reduced as flow levels increased, reducing eutrophication and resulting in recovering forest stands. In addition, the lowering water levels would result in encroachment of the forest along the lake shore. This cycle occurred many times in the history of this lake as indicated by fluctuations in the size of arcellacean populations.
Midge-inferred Holocene climate history of two subalpine lakes in southern British Columbia, Canada
The Holocene, 2004
To investigate postglacial environmental changes in both the coastal and interior wet belts of British Columbia, fossil midges were analysed from two subalpine lakes, one adjacent to the lower Fraser canyon (Frozen Lake), and the other in Mount Revelstoke National Park (Eagle Lake). The midge stratigraphy for Frozen Lake revealed an abundance of rheophilous chironomid taxa and Simuliidae larvae, re ecting the presence of an in owing stream. An abundance of Chaoborus mandibles and Microtendipes during the early Holocene (c. 10100-7700 14 C years BP, c. 11500-8500 cal. years BP) suggests warmer temperatures. A subsequent decline in the warm indicators and relative increases in cold stenotherms (Heterotrissocladius and Diamesa) indicate cooling until present day. This climate reconstruction is consistent with other quantitative and qualitative evidence for past climatic change in southern British Columbia. At Eagle Lake the warm indicators, Dicrotendipes and Polypedilum, are seen in the early Holocene (c. 8500-6730 14 C years BP, c. 9600-7600 cal. years BP), but are absent during the mid-Holocene when cooler temperatures probably prevailed. In the late Holocene (c. 3800 14 C years BP to present, c. 4200 cal. years BP to present) there is a resurgence of warm indicators, which contrasts with the evidence of continued cooling typically seen in reconstructions of southern British Columbia summer temperatures. The Eagle Lake record therefore appears to be anomalous. Multiproxy and multisite investigations are needed to reconstruct Holocene climatic changes more reliably.