The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform
Melinda Moeur - One of the best experts on this subject based on the ideXlab platform.
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Spatial models of competition and gap dynamics in old-growth Tsuga heterophylla/Thuja plicata forests
Forest Ecology and Management, 1997Co-Authors: Melinda MoeurAbstract:Abstract Stem-mapped plots in old-growth forests of western hemlock ( Tsuga heterophylla ) and western redcedar ( Thuja plicata ) in northern Idaho, USA were analyzed using Ripley's K ( d ) function, nearest-neighbor function, and influence zone analyses. A conceptual model of old-growth forest development was formulated from the spatial pattern analyses, to guide the development of a mathematical model. In the conceptual model, cohorts of seedlings begin life established in clusters associated with canopy gaps created by the deaths of overstory trees. Then, as the trees within clusters increase in size, they begin to compete with their immediate neighbors. Density-dependent mortality thins the clusters and increases the distance between neighboring trees. Over time, this self-thinning behavior tends to drive stand spatial patterns from aggregation towards regular spacing as trees get larger or increase in competitive status. Preliminary results from a dynamic point process model are presented. The approach simulates the regeneration of seedlings in gaps and the dynamic spatial patterns resulting from competitive interactions between neighboring trees as a sequence of point processes. Main features of the model are stochastic assignment of gapmaker trees, a Poisson cluster process for regeneration establishment, and a progressive simple inhibition process for competition between neighboring trees. The model produces spatial patterns for regeneration and adult trees consistent with the conceptual model and with patterns observed in the field data. Refinements designed to improve model realism are discussed.
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spatial models of competition and gap dynamics in old growth Tsuga heterophylla thuja plicata forests
Forest Ecology and Management, 1997Co-Authors: Melinda MoeurAbstract:Abstract Stem-mapped plots in old-growth forests of western hemlock ( Tsuga heterophylla ) and western redcedar ( Thuja plicata ) in northern Idaho, USA were analyzed using Ripley's K ( d ) function, nearest-neighbor function, and influence zone analyses. A conceptual model of old-growth forest development was formulated from the spatial pattern analyses, to guide the development of a mathematical model. In the conceptual model, cohorts of seedlings begin life established in clusters associated with canopy gaps created by the deaths of overstory trees. Then, as the trees within clusters increase in size, they begin to compete with their immediate neighbors. Density-dependent mortality thins the clusters and increases the distance between neighboring trees. Over time, this self-thinning behavior tends to drive stand spatial patterns from aggregation towards regular spacing as trees get larger or increase in competitive status. Preliminary results from a dynamic point process model are presented. The approach simulates the regeneration of seedlings in gaps and the dynamic spatial patterns resulting from competitive interactions between neighboring trees as a sequence of point processes. Main features of the model are stochastic assignment of gapmaker trees, a Poisson cluster process for regeneration establishment, and a progressive simple inhibition process for competition between neighboring trees. The model produces spatial patterns for regeneration and adult trees consistent with the conceptual model and with patterns observed in the field data. Refinements designed to improve model realism are discussed.
Robert L Edmonds - One of the best experts on this subject based on the ideXlab platform.
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Vegetation in the West Twin Creek Watershed: Tree Population Dynamics, Growth and Mortality in Old-Growth Forests in the Western Olympic Mountains, Washington
1993Co-Authors: Robert L EdmondsAbstract:Plant communities were classified and relationships between the environment and vegetation were examined in old-growth forests in a small watershed in the Hoh River valley of western Olympic National Park; West Twin Creek (58 ha, 180-850 m). Detrended correspondence analysis (DECORANA) was used to ordinate the data. Elevation and slope were the primary environmental gradients. Two-way indicator species analysis (TWINSPAN) was used to classify the data. Five distinct community types were classified and described in West Twin Creek watershed. The most widespread community in the lower watershed was the Tsuga heterophylla/Polystichum munitum/Oxalis oregana type which had two variants. The second type in the lower watershed was the Tsuga heterophylla/Gaultheria shallon type. Three community types occurred in the upper watershed (Tsuga heterophylla-Abies amabilis/Vaccinium alaskaense, Tsuga heterophylla/Oxalis oregana and Tsuga heterophylla-Abies amabilis/Depauparate. Community composition was highly variable in the West Twin Creek Watershed (2-16 understory species/0.1 ha plot). Tree density was greatest in disturbed communities caused by windfelled trees at West Twin Creek.
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Vegetation in the West Twin Creek Watershed: Tree Population Dynamics, Growth and Mortality in Old-Growth Forests in the Western Olympic Mountains, Washington
1993Co-Authors: Robert L EdmondsAbstract:Plant communities were classified and relationships between the environment and vegetation were examined in old-growth forests in a small watershed in the Hoh River valley of western Olympic National Park; West Twin Creek (58 ha, 180-850 m). Detrended correspondence analysis (DECORANA) was used to ordinate the data. Elevation and slope were the primary environmental gradients. Two-way indicator species analysis (TWINSPAN) was used to classify the data. Five distinct community types were classified and described in West Twin Creek watershed. The most widespread community in the lower watershed was the Tsuga heterophylla/Polystichum munitum/Oxalis oregana type which had two variants. The second type in the lower watershed was the Tsuga heterophylla/Gaultheria shallon type. Three community types occurred in the upper watershed (Tsuga heterophylla-Abies amabilis/Vaccinium alaskaense, Tsuga heterophylla/Oxalis oregana and Tsuga heterophylla-Abies amabilis/Depauparate. Community composition was highly variable in the West Twin Creek Watershed (2-16 understory species/0.1 ha plot). Tree density was greatest in disturbed communities caused by windfelled trees at West Twin Creek.
Carol Ritland - One of the best experts on this subject based on the ideXlab platform.
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Microsatellite markers in western hemlock [Tsuga heterophylla (Raf.) Sarg]
Molecular Ecology Notes, 2003Co-Authors: Hugh Wellman, Emily S. Pritchard, Andy Benowicz, Dilara Ally, Carol RitlandAbstract:Fifteen microsatellite markers have been isolated from western hemlock [Tsuga heterophylla (Raf.) Sarg] genomic DNA and six of these markers were optimized for use in mountain hemlock [Tsuga mertensiana (Bong) Carr.]. The mean expected heterozygosity (HE) was 0.88 and 0.89 for western hemlock and mountain hemlock, respectively. Allelic diversity was high for both hemlock species, ranging from 7 to 15 alleles per locus for western hemlock and 5–30 alleles per locus for mountain hemlock. The allelic variation identified in this project will allow monitoring of changes in genetic variation as a result of selection pressure in breeding programs.
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Genetic effects of domestication in western hemlock, Tsuga heterophylla
2003Co-Authors: Hugh Wellman, Carol Ritland, Kermit Ritland, H. WellmanAbstract:Rates of genetic diversity were inferred from allelic variation in western hemlock (Tsuga heterophylla (Raf.) Sarg) using starch gel electrophoresis. Nine enzyme stains were employed to identify fourteen isozyme loci. The concluding allelic variation was then used to compare differing orchard conditions with natural stands of western hemlock. The main goal was to measure the effectiveness of seed orchard and seed collection protocol in maintaining natural genetic structure. A measure of gene diversity, H, was fairly high for both the natural populations (0.146) and the seed orchard populations, within which it ranged from 0.141 for full-sib orchards (FS) to 0.164 for the offspring from supplemental mass pollination (SMP). Large amounts of genetic variation in western hemlock accords with the life history and patterns of morphological and physiological variability. This trend was also seen in observed heterozygosity H, (0.154) for the SMP compared to the unimproved orchards (0.136). These results indicate that the maintenance of genetic diversity may be higher for the SMP treatment. This is expected as SMP have been shown to minimize self-fertilization, increase the genetic base through the
Richard J. Hebda - One of the best experts on this subject based on the ideXlab platform.
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Coastal rainforest connections disclosed through a Late Quaternary vegetation, climate, and fire history investigation from the Mountain Hemlock Zone on southern Vancouver Island, British Colombia, Canada
Review of Palaeobotany and Palynology, 2002Co-Authors: K. J. Brown, Richard J. HebdaAbstract:Abstract The post-glacial vegetation and fire history of high-elevation regions on southern Vancouver Island is described using palynological and charcoal records from Porphyry and Walker lakes. A zone consisting mainly of Artemisia , Poaceae, and ferns occurs in the basal clay at Porphyry Lake and may represent a non-arboreal ecosystem in a late-Wisconsin glacial refugium. At both sites, a fire-free Pinus contorta zone occurs before ca 14 160 calendar years before present (cal BP). Climate at this time is interpreted as being cool to cold and dry. Mixed conifer forests of Picea , Abies , Tsuga mertensiana and Pinus contorta replaced the Pinus contorta woodlands after ca 14 160 cal BP. Fires are recorded for the first time. Climate is interpreted as cool and moist. Forests of Abies , Picea , Tsuga heterophylla , PseudoTsuga menziesii , and Alnus developed and expanded during the early-Holocene from ca 11 400–9910 to 7700–7300 cal BP as climate warmed and dried. Charcoal increased during this interval, indicating only slightly more fire activity and reflecting continued moist conditions at high elevations. In the mid-Holocene from ca 7700–7300 to 5200–4900 cal BP, Tsuga heterophylla pollen values increased as forests became dominated by Tsuga heterophylla , Picea , and Abies with Alnus in response to increased moisture. The increase in charcoal influx at this time may reflect an increase in slope wash and erosion resulting from a wetter climate rather than an increase in fire incidence. Starting at ca 5200–4900 cal BP, a further increase in Tsuga heterophylla combined with an increase in Tsuga mertensiana and Cupressaceae pollen suggest that the late-Holocene was characterised by increasing moisture and decreasing temperatures. Late-Holocene forests consisted predominately of Tsuga heterophylla , Tsuga mertensiana , Cupressaceae, and Pinus contorta . A slight reduction in charcoal influx at ca 4600 cal BP implies fewer fires. A recent increase in charcoal at Walker Lake at 1700 cal BP may reflect anthropogenic burning. The timing of events and response of taxa on southern Vancouver Island are comparable to other coastal sites in northwestern North America, suggesting that past ecosystems were widespread and contemporaneous. Palaeoecosystem changes detected in one region of the Pacific Northwest likely reflect a widepsread response to climate throughout the ∼2500 km long zone, a zone that today is home to half of the world’s remaining coastal temperate rainforest.
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Surface pollen spectra from southern Vancouver Island, British Columbia, Canada
Canadian Journal of Botany, 1999Co-Authors: Gregory B. Allen, K. J. Brown, Richard J. HebdaAbstract:Analyses of surface samples of 84 sites from southern Vancouver Island were used to characterize pollen and spore spectra of modern vegetation types. Xeric Quercus garryana Dougl. and grassland associations can be identified by Quercus pollen and abundant nonarboreal pollen, respectively. Coastal Douglas-fir (PseudoTsuga menziesii var. menziesii (Mirb.) Franco) forests are distinguished by high proportions of PseudoTsuga and low PseudoTsuga to Tsuga heterophylla (Raf.) Sarg. ratios. Coastal Western Hemlock zone forests have abundant Tsuga heterophylla pollen. Dry Coastal Western Hemlock subzones have diagnostically abundant PseudoTsuga and Tsuga heterophylla pollen, and intermediate PseudoTsuga to Tsuga heterophylla ratios. Moist Coastal Western Hemlock variants are characterised by little or no PseudoTsuga pollen and high PseudoTsuga to Tsuga heterophylla ratios. The Mountain Hemlock zone exhibits abundant Tsuga mertensiana (Bong.) Carr. pollen percentages and notable nonarboreal pollen and spore values....
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Modem pollen spectra from west central British Columbia
Canadian Journal of Botany, 1993Co-Authors: Richard J. Hebda, Gregory B. AllenAbstract:Sixty-four moss and organic litter samples were collected from five biogeoclimatic zones distributed from sea level on the central coast of British Columbia onto the western edge of the Interior Plateau at 1000 – 1900 m and analyzed for pollen and spores. Four of the five biogeoclimatic zones produced characteristic pollen and spore spectra. The coastal western hemlock biogeoclimatic zone is characterized by Tsuga heterophylla, Alnus, and Cupressaceae. Significant levels of nonarboreal pollen (NAP), mainly Lysichiton and fern spores, occur in some sites. Interior Douglas-fir zone samples are dominated by PseudoTsuga and Tsuga heterophylla with notable Betula, Cupressaceae, and Alnus. Pinus pollen becomes the dominant type at the eastern margins of the interior Douglas-fir zone and dominates the Engelmann spruce – subalpine fir, montane spruce, and sub-boreal pine–spruce biogeoclimatic zones at high and intermediate elevations to the east. In the Engelmann spruce – subalpine fir zone, Abies pollen is chara...
Hugh Wellman - One of the best experts on this subject based on the ideXlab platform.
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Microsatellite markers in western hemlock [Tsuga heterophylla (Raf.) Sarg]
Molecular Ecology Notes, 2003Co-Authors: Hugh Wellman, Emily S. Pritchard, Andy Benowicz, Dilara Ally, Carol RitlandAbstract:Fifteen microsatellite markers have been isolated from western hemlock [Tsuga heterophylla (Raf.) Sarg] genomic DNA and six of these markers were optimized for use in mountain hemlock [Tsuga mertensiana (Bong) Carr.]. The mean expected heterozygosity (HE) was 0.88 and 0.89 for western hemlock and mountain hemlock, respectively. Allelic diversity was high for both hemlock species, ranging from 7 to 15 alleles per locus for western hemlock and 5–30 alleles per locus for mountain hemlock. The allelic variation identified in this project will allow monitoring of changes in genetic variation as a result of selection pressure in breeding programs.
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Genetic effects of domestication in western hemlock, Tsuga heterophylla
2003Co-Authors: Hugh Wellman, Carol Ritland, Kermit Ritland, H. WellmanAbstract:Rates of genetic diversity were inferred from allelic variation in western hemlock (Tsuga heterophylla (Raf.) Sarg) using starch gel electrophoresis. Nine enzyme stains were employed to identify fourteen isozyme loci. The concluding allelic variation was then used to compare differing orchard conditions with natural stands of western hemlock. The main goal was to measure the effectiveness of seed orchard and seed collection protocol in maintaining natural genetic structure. A measure of gene diversity, H, was fairly high for both the natural populations (0.146) and the seed orchard populations, within which it ranged from 0.141 for full-sib orchards (FS) to 0.164 for the offspring from supplemental mass pollination (SMP). Large amounts of genetic variation in western hemlock accords with the life history and patterns of morphological and physiological variability. This trend was also seen in observed heterozygosity H, (0.154) for the SMP compared to the unimproved orchards (0.136). These results indicate that the maintenance of genetic diversity may be higher for the SMP treatment. This is expected as SMP have been shown to minimize self-fertilization, increase the genetic base through the
