Topic
Tsuga
About: Tsuga is a research topic. Over the lifetime, 1279 publications have been published within this topic receiving 43359 citations.
Papers published on a yearly basis
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Papers
TL;DR: In a maple-beech forest in eastern New York, equal numbers of mounds, pits, and adjacent undisturbed soil microsites were censused for plant species density and cover over the growing seasons of 1978 and 1979, microrelief created a mosaic of soil properties and a vegetation pattern in the understory, both of which were affected by the presence of hemlock in the canopy.
Abstract: In a maple-beech forest in eastern New York, equal numbers of mounds, pits, and adjacent undisturbed soil microsites were censused for plant species density and cover over the growing seasons of 1978 and 1979. Several soil properties were also measured for each microsite. Detrended correspondence analysis (DCA) and chi-square goodness-of-fit tests were used to test whether the species were uniformly distributed over the microrelief positions. Comparisons of species composition, diversity, and vegetative phenologies were made between microsites and between hemlock- and hard- wood-dominated forest areas. Differences in soil properties between microsites and between the two forest areas were assessed with one-tailed paired t tests and Wilcoxon rank-sum tests, respectively. Microrelief created a mosaic of soil properties and a vegetation pattern in the understory, both of which were affected by the presence of hemlock in the canopy. Ordinations (DCA) indicated two factors that affected species composition of the microsites: (1) presence of hemlock (Tsuga canadensis) as the nearest canopy tree, and (2) microtopography (whether the microsite was a mound, pit, or undisturbed-soil site). Species in non-hemlock areas had patchy distributions in the forest community: eight species grew mainly on mounds, six in pits, and five on undisturbed soil. The mounds and pits had characteristic assemblages of species. Species richness and total density and cover of plants in each microsite were constant over the growing season. In contrast, little spatial or temporal community pattern was apparent in forest areas influenced by hemlock. The effect of hemlock on species distributions was due in part to its effect on soil properties. For all microsites, forest areas with hemlock had greater soil organic matter content, available nitrogen, cation exchange capacity, and litter depth, lower soil calcium content, moisture content, temperature, pH, and A, horizon depth; and no frost heaving. Microrelief also affected soil properties significantly. In comparison with pits, mounds were drier and poorer in nutrient content, and had a lower cation exchange capacity, less organic matter, less litter cover, a thinner A, horizon, and less snow accumulation. In areas without hemlock, the mounds were also more acid, warmer in summer and colder in winter, and more subject to frost heaving than pits. Hemlock-influenced areas had no consistent microsite differences in pH or temperature. The different microenvironments, created by the interaction of microrelief and hemlock, resulted in patchy distributions of most understory species. This pattern was likely a result of species require- ments for and tolerances of environmental conditions, tempered by competitive interactions.
550 citations
TL;DR: Responses of stocking density, growth, mortality, and regeneration for three conifer species from the clear-cut edge into the interior of old-growth forest patches adjacent to 10-15 yr old clearcuts in southern Washington and central Oregon are described.
Abstract: Forest edges created by dispersed-patch clear-cutting have become a con- spicuous landscape feature in western North America, but the effects of edge on forest structure and function are still poorly understood. In this paper we describe responses of stocking density, growth, mortality, and regeneration for three conifer species from the clear-cut edge into the interior of old-growth forest patches adjacent to 10-15 yr old clearcuts in southern Washington and central Oregon. The significance of edge effects for each variable was tested through a single-factor (distance) analysis of variance (F test). Relationships between these variables and depth-of-edge influence (i.e., edge width) on old-growth forest were characterized by nonlinear regression models. Near the edge (forest-clearcut boundary line), the old-growth forest has (1) reduced stocking density, as measured by canopy cover, number of stems per hectare, and basal area; (2) increased growth rates of dominant Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla), as calcu- lated by an index of relative growth rate; (3) elevated rates of tree mortality, as measured by standing dead and down trees (snags and logs); and (4) greater numbers of Douglas-fir and western hemlock seedlings (<100 cm tall) and saplings (10 1-200 cm) but fewer of Pacific silver fir (Abies amabilis). The depth-of-edge influence, when calculated as the point along the clearcut-forest gradient at which a given variable has returned to a condition representing 2/3 of the interior forest environment, ranged from 16 to 137 m for variables related to distance from the edge. The amount of a square forest patch affected by edge decreased as patch size increased and varied greatly with the depth-of-edge influence. With increasing concerns about organisms and processes that require interior forest habitat, determining the area of residual forest influenced by adjacent clearcut is critical to current and future resource management. Responses of additional biological variables must be explored and information on edge phenomena should be extended to the scale of landscapes.
547 citations
TL;DR: Extensions of traditional distance-dependent, spatial competition analyses that estimate the magnitude of the competitive effects of neighboring trees on target tree growth as a function of the species, size, and distance to neighboring trees are developed.
Abstract: We have developed extensions of traditional distance-dependent, spatial competition analyses that estimate the magnitude of the competitive effects of neighboring trees on target tree growth as a function of the species, size, and distance to neighboring trees. Our analyses also estimate inter- and intra-specific competition coefficients and ex- plicitly partition the competitive effects of neighbors into the effects of shading versus crowding. We tested the method using data from forests of northern, interior British Columbia dominated by western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don). For both species, the most parsimonious regression models included terms for the effects of tree size, crowding, and shading and separate competitive effects of four dif- ferent groups of competing species. The models explained 33%-59% of the variation in radial growth of the two spe- cies. For both species, growth declined more steeply as a function of crowding than shading. There was striking asymmetry in the strength of interspecific competition between hemlock and redcedar, with crowding by hemlock hav- ing a strong per capita effect on redcedar, while crowding by redcedar had relatively little effect on the radial growth of hemlock.
515 citations
TL;DR: Dramatic reductions in T. canadensis across broad geographical areas appear imminent if HWA dispersal continues unimpeded and no effective natural enemies of HWA are found.
Abstract: ORWIG, D. A. AND D. R. FOSTER (Harvard University, Harvard Forest, Petersham, Massachusetts 01366). Forest response to the introduced hemlock woolly adelgid in southern New England, USA. J. Torrey Bot. Soc. 125:60-73. 1998.-Hemlock woolly adelgid (HWA), Adelges tsugae, an introduced aphid-like insect from Asia, is expanding its range across the northeastern United States through the range of Tsuga canadensis (eastern hemlock) and can severely reduce or eliminate this important late-successional species. As part of a study investigating standand landscape-level forest dynamics resulting from HWA infestation, we examined initial community response of eight T. canadensis stands in south-central Connecticut. Our major objectives were to assess mortality patterns in T. canadensis, evaluate subsequent changes in stand microenvironment, and relate these and stand composition to initial patterns of regeneration, understory response, and community reorganization. Tsuga canadensis damage varied broadly across the study area ranging from near zero to greater than 95% mortality. All size and age classes sampled were attacked by HWA, although smaller trees exhibited higher mortality rates than larger trees. All remaining T. canadensis sampled in seven of the eight stands were infested with HWA and over 90% suffered at least 50% foliar loss. Substantial accumulations of downed woody debris have developed in stands with severe HWA damage. Canopy gaps created by HWA damage significantly increased the amount of light reaching the forest floor and resulted in rapid understory vegetation responses. Prolific Betula lenta (black birch) establishment occurred in stands with moderate to severe T. canadensis mortality. In addition, opportunistic herbaceous species (Erechtites hieracifolia, Phytolacca americana) and exotic species (Ailanthus altissima, Microstegium vimineum) have recently invaded these stands. Due to mortality from HWA, T. canadensis seedlings were scarce in sampled stands, suggesting that advance regeneration and seedbanks will not be important mechanisms for T. canadensis reestablishment. Tsuga canadensis cannot sprout following defoliation and has no apparent resistance to HWA. Therefore, dramatic reductions in T. canadensis across broad geographical areas appear imminent if HWA dispersal continues unimpeded and no effective natural enemies of HWA are found.
500 citations
TL;DR: White-tailed deer have increased in abundance and expanded their geographic range in North America over the past century, and now exist at higher densities than they have in the past several hundred years, having numerous impacts on the forest ecosystems they inhabit.
Abstract: Summary White-tailed deer have increased in abundance and expanded their geographic range in North America over the past century, and now exist at higher densities than they have in the past several hundred years. This is having numerous impacts on the forest ecosystems they inhabit. Regional recruitment failure of eastern hemlock (Tsuga canadensis) and northern white cedar (Thuja occidentalis) trees can be explained in part by deer browsing. Deer also have significant negative effects on understorey plants, including wild lily-of-the-valley (Maianthemum canadense) and whiteflowered trillium (Trillium grandiflorum). Long-term studies of primary, old-growth forest stands reveal a 48‐81 per cent herb and shrub species loss accompanying increases in deer density. Graminoids, ferns and club mosses were more likely to persist in these stands than plants in all other taxonomic groups. Deer also exhibit indirect effects on forest communities by reducing host plant densities or altering forest structure. Because of their numerous direct and indirect effects on other species, and because of the magnitude of these effects, white-tailed deer act as a keystone herbivore. Natural regulation and maximum sustained yield management approaches have failed to alleviate deer impacts on forest ecosystems, but an ecosystem-based management approach offers promise.
449 citations
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Performance Metrics
| Year | Papers |
|---|---|
| 2026 | 1 |
| 2025 | 10 |
| 2024 | 12 |
| 2023 | 33 |
| 2022 | 57 |
| 2021 | 29 |