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Jack Pine (jack + pine)

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Life Sciences60%

Selected Abstracts

Late-glacial and Holocene palaeovegetation zonal reconstruction for central and north-central North America

JOURNAL OF BIOGEOGRAPHY, Issue 6 2005
W. L Strong
Abstract Aim, The purpose of this study is to develop palaeovegetation zonation models for central and north-central North America, based on late-Quaternary and Holocene pollen stratigraphic data (n = 246 sites). A secondary purpose was to evaluate an hypothesis (Strong & Hills, 2003) to explain the disjunct distribution of species in western Alberta. Location, Hudson Bay-Lake Michigan to the Rocky Mountains region, north of 36° N to the Arctic Ocean (c. 70° N). Methods, Pollen profiles spanning 40 years of palaeoecological research in North America were extracted from published and unpublished archival sources. Individual profiles were subdivided into 1000-year increments based on the assumption of a constant sedimentation rate between stratigraphic dates (e.g. surface sediments, radiocarbon 14C dates, tephra layers). The pollen composition among profiles was standardized to 54 commonly recognized taxa, with percentage composition within each stratigraphic sample prorated to 100% prior to analysis. Near-surface sediments from these profiles were included as analogues of modern vegetation. Cluster analysis was used as a guide to the classification of 2356 temporal stratigraphic samples, which resulted in the recognition of 16 pollen groups. These groups were summarized in terms of their pollen composition, mapped, and used in combination with terrain information and an ecological knowledge of the study area to construct six physiognomically-based palaeovegetation zonation models at 2000-year intervals from 14,000 to 4000 yr bp (radiocarbon years before present). Results, The 14,000 yr bp model placed Boreal and Cordilleran Forests proximal to the southern glacial front, whereas Arctic tundra dominated the Yukon Territory,Alaska ice-free zone. Pollen and macrofossil evidence suggests that this Boreal Forest zone contained a mixture of coniferous and deciduous tree species. Grassland was postulated immediately south of the forest zone, with its northern extreme near 49° N latitude in the Alberta,Montana border area. Separation of the Laurentide and Cordilleran glacial fronts about 12,000 yr bp initiated the northward advance of Boreal Forests into western Canada. By the end of the Hypsithermal at about 6000 yr bp, Boreal Forests occurred near the Arctic Ocean, and Grassland and Aspen Parkland zones may have extended to 54° N and 59° N latitude in Alberta, respectively. Between 6000 and 4000 yr bp, a 5° and 1° latitudinal southward shift of the northern Boreal Forest and Grassland/Aspen Parkland boundaries occurred, respectively, near their contemporary positions with corresponding expansions of the Subarctic and Arctic zones. Modern Canadian Cordilleran Forests along the eastern slopes of the Rocky Mountains were interpreted as originating from the north-central Montana,south-western Alberta area. Jack pine (Pinus banksiana Lamb.), a common Boreal Forest species, appears to have entered central Canada via the north side of Lake Superior after 11,000 yr bp. Main conclusions, Modern vegetation in central Canada evolved from biomes located in the northern USA during the late-Quaternary. The Boreal Forest biome contained the same arboreal taxa as the modern vegetation, except it lacked jack pine. The proposed regional palaeovegetation models support the hypothesis of Strong & Hills (2003), but new independent palaeoecological data will be needed for a proper evaluation. [source]

A comparison of heat pulse velocity and lesion lengths for assessing the relative virulence of mountain pine beetle-associated fungi on jack pine

FOREST PATHOLOGY, Issue 4 2008
A. V. Rice
Summary The mountain pine beetle (MPB) vectors three blue-stain fungi, Grosmannia clavigera, Ophiostoma montium and Leptographium longiclavatum, which contribute to the success of the beetles and the death of the trees. The utility of two methods, heat pulse velocity (HPV) and lesion length, for assessing the relative virulence of these fungi were compared on jack pine in central Alberta. The HPV monitoring apparatus failed to detect xylem sap flow in any of the trees and, thus, could not be used to assess fungal virulence. In contrast, measurement of lesion lengths was more sensitive and provided further evidence that G. clavigera and L. longiclavatum are more virulent than O. montium. The failure of the HPV apparatus to detect sap flow suggests that the study trees were moisture stressed, a factor likely to increase their susceptibility to MPB. Thus, this method is not appropriate for assessing the response of the most susceptible (i.e. drought stressed) trees to MPB and its associated fungi. [source]

Late-glacial and Holocene palaeovegetation zonal reconstruction for central and north-central North America

JOURNAL OF BIOGEOGRAPHY, Issue 6 2005
W. L Strong
Abstract Aim, The purpose of this study is to develop palaeovegetation zonation models for central and north-central North America, based on late-Quaternary and Holocene pollen stratigraphic data (n = 246 sites). A secondary purpose was to evaluate an hypothesis (Strong & Hills, 2003) to explain the disjunct distribution of species in western Alberta. Location, Hudson Bay-Lake Michigan to the Rocky Mountains region, north of 36° N to the Arctic Ocean (c. 70° N). Methods, Pollen profiles spanning 40 years of palaeoecological research in North America were extracted from published and unpublished archival sources. Individual profiles were subdivided into 1000-year increments based on the assumption of a constant sedimentation rate between stratigraphic dates (e.g. surface sediments, radiocarbon 14C dates, tephra layers). The pollen composition among profiles was standardized to 54 commonly recognized taxa, with percentage composition within each stratigraphic sample prorated to 100% prior to analysis. Near-surface sediments from these profiles were included as analogues of modern vegetation. Cluster analysis was used as a guide to the classification of 2356 temporal stratigraphic samples, which resulted in the recognition of 16 pollen groups. These groups were summarized in terms of their pollen composition, mapped, and used in combination with terrain information and an ecological knowledge of the study area to construct six physiognomically-based palaeovegetation zonation models at 2000-year intervals from 14,000 to 4000 yr bp (radiocarbon years before present). Results, The 14,000 yr bp model placed Boreal and Cordilleran Forests proximal to the southern glacial front, whereas Arctic tundra dominated the Yukon Territory,Alaska ice-free zone. Pollen and macrofossil evidence suggests that this Boreal Forest zone contained a mixture of coniferous and deciduous tree species. Grassland was postulated immediately south of the forest zone, with its northern extreme near 49° N latitude in the Alberta,Montana border area. Separation of the Laurentide and Cordilleran glacial fronts about 12,000 yr bp initiated the northward advance of Boreal Forests into western Canada. By the end of the Hypsithermal at about 6000 yr bp, Boreal Forests occurred near the Arctic Ocean, and Grassland and Aspen Parkland zones may have extended to 54° N and 59° N latitude in Alberta, respectively. Between 6000 and 4000 yr bp, a 5° and 1° latitudinal southward shift of the northern Boreal Forest and Grassland/Aspen Parkland boundaries occurred, respectively, near their contemporary positions with corresponding expansions of the Subarctic and Arctic zones. Modern Canadian Cordilleran Forests along the eastern slopes of the Rocky Mountains were interpreted as originating from the north-central Montana,south-western Alberta area. Jack pine (Pinus banksiana Lamb.), a common Boreal Forest species, appears to have entered central Canada via the north side of Lake Superior after 11,000 yr bp. Main conclusions, Modern vegetation in central Canada evolved from biomes located in the northern USA during the late-Quaternary. The Boreal Forest biome contained the same arboreal taxa as the modern vegetation, except it lacked jack pine. The proposed regional palaeovegetation models support the hypothesis of Strong & Hills (2003), but new independent palaeoecological data will be needed for a proper evaluation. [source]

The millennial dynamics of a boreal forest stand from buried trees

JOURNAL OF ECOLOGY, Issue 3 2004
DOMINIQUE ARSENEAULT
Summary 1We reconstructed the dynamics of a black spruce (Picea mariana) and jack pine (Pinus banksiana) forest stand in northern Québec using a continuous, 5200-year-long sequence of stem remains buried in adjacent peatland. Simulations of recruitment of such remains provided guidelines for inferring past ecosystem structure and composition at the stand scale. 2Compared with the late Holocene (4650,0 cal. year BP (CYBP)), the mid Holocene (5200,4650 CYBP) period was characterized by faster tree growth, larger stems and higher stem density, indicating higher forest productivity in association with a milder climate. 3The presence of stem remains of both species from 17 out of 20 contiguous 250-year time intervals suggests that the spruce-pine stand exhibited high compositional stability, with both species regenerating after fire from canopy-stored seed banks. 4Relative species abundance closely followed the duration of past fire intervals deduced from the number of tree rings in buried conifers. Time periods of long (4650,3950, 3400,1850 and 250,0 CYBP) and short fire intervals (4950,4650, 3950,3400 and 1850,250 CYBP) were associated, respectively, with decreasing and increasing pine abundance, probably reflecting faster juvenile growth, lower shade tolerance, earlier sexual maturity and shorter longevity in jack pine compared with black spruce. 5We conclude that both climate change and climate-induced fire disturbance have been driving long-term ecosystem dynamics. Our field evidence supports the idea that interactions between disturbances and the life-history traits of species modulate the impact of climate change at the scale of forest stands. At the same time, disturbances may result in long-term stability of disturbance-adapted ecosystems. [source]