Browsing by Subject "Betula alleghaniensis"

Now showing 1 - 4 of 4
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    Are shade tolerance, survival, and growth linked? Low light and nitrogen effects on hardwood seedlings
    (1996) Walters, Michael B; Reich, Peter B
    Variation in shade tolerance is a primary mechanism driving succession in northern deciduous forests. However, little is known about interspecific differences in the traits responsible for shade tolerance. Is shade tolerance due to the ability to grow or survive in deep shade, or both? How do plant morphology and photosynthesis relate to growth in shade? Is low light the sole critical stress determining differences in "shade tolerance" or do below ground resources interact with low light to affect growth and survival? In this study we address these questions for seedlings of Betula papyrifera Marsh., Betula alleghaniensis Britton, Ostrya virginiana (Mill.) K. Koch, Acer saccharum Marsh., and Quercus rubra L. grown for 2 yr in outdoor shade houses in a complete factorial of low light (2 and 8% open sky) and nitrogen (forest soil and forest soil plus 200 kg N.ha-'.yr-'). For these seedlings we examined effects of light and nitrogen on the interrelationships among survival, growth, and shade tolerance and explored the physiological bases of shade tolerance by examining the relationship of plant morphology and photosynthesis to growth. Nitrogen amendments did not have a significant effect on any plant trait at either light level. In 8% light, growth and survival were highest for shade-intolerant Betula papyrifera and mid-tolerant Betula alleghaniensis, lower for shade-tolerant Ostrya and Acer, and lowest for disturbance-adapted Quercus. In 2% light, species rankings reversed as Ostrya and Acer had higher growth and survival than the other species. Second-year survival was strongly related to 1st-yr growth (P < 0.001), whereas relationships with 1st-yr plant mass and 1styr absolute growth rates were weak. Therefore, survival of shade-tolerant species at 2% light was related to their maintenance of positive growth, whereas intolerant species had growth near zero and high rates of mortality. In both 2 and 8% light photosynthetic rates on mass (but not area) bases and the proportion of the plant in leaves (leaf area ratio and leaf mass ratio) were positively related to growth. Greater rates of growth and survival for shade-tolerant species in very low light, and for intolerant species in higher light, suggest that there is a species-based trade-off between maximizing growth in high light and minimizing the light compensation point for growth. This trade-off may be an important mechanism driving forest community dynamics in northern hardwood forests.
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    The influence of natural disturbance-based silviculture treatments on northern hardwood forests in Northeastern Minnesota, USA.
    (2010-12) Bolton, Nicholas William
    Natural disturbance-based silviculture (NDBS) has been suggested as an approach for promoting late-successional forest characteristics and maintaining native biodiversity in managed forests. Harvest gaps based on the natural disturbance patterns found in the upper Great Lakes (46 study gaps) were created throughout northern hardwood forests in northeastern Minnesota, USA, during the winters of 2002 and 2003. Gaps were measured 6- and 7-years post-treatment and subsequent analysis of these measurements was used to evaluate the success of these treatments at meeting structural and compositional objectives. Results indicated that these gaps have done little to increase tree diversity, including the recruitment of shade mid-tolerant species; however, the richness of herbaceous understory vegetation has responded positively to larger gap sizes. Herbaceous species increasing in harvest gaps included Actaea spp. L. (baneberry), Botrychium virginianum L. (rattlesnake fern), Mertensia paniculata Aiton (Northern bluebell), Rubus idaeus L. (red raspberry), Sanguinaria canadensis L. (bloodroot) and Cirsium arvense L. (Canada thistle). Results also indicated that subtle patterns were found among species spatial establishment within gaps (e.g., gap edge and gap center) and species that expressed no preference between the intact forest and harvest gaps. Levels of downed coarse woody debris (CWD) differed among gap size and all gaps had lower levels of CWD compared to the surrounding intact forest. Due to the historical importance of Betula alleghaniensis in these systems, the factors affecting the recruitment of this species were also investigated. Based on these investigations, it was found that B. alleghaniensis establishment was strongly related to highly decayed, large coniferous pieces of CWD with little recruitment occurring on the undisturbed forest floor. As such, providing appropriate seedbed conditions for shade mid-tolerant species and utilizing natural canopy gap sizes would improve the success of maintaining this species on the landscape.
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    Initial effects of structural complexity restoration treatments and deer browsing on ground-layer community composition and tree regeneration in northern hardwood forests
    (2014-03) Reuling, Laura F.
    As researchers realize the value of old-growth forests and their unique attributes and dynamics, managers have begun developing management regimes aimed at restoring old-growth characteristics in forests managed for wood products. However, changes in these forests since European settlement, especially increased population of white-tailed deer (Odocoileus virginianus Zimmerman) may have important implications for forest composition and regeneration. The objective of this research was to determine the initial (three- and four-year) effects of several old-growth structural restoration treatments and browsing by white-tailed deer on tree regeneration and understory community composition in northern hardwood forests in northern Wisconsin, USA. Community composition and tree regeneration were measured in stands with six different silvicultural treatments replicated across three large study areas (> 50 ha). Treatments consisted of a combination of two levels of coarse woody debris and three overstory gap treatments designed to emulate patterns of natural gap and mesoscale canopy disturbance: small gaps (10.7m diameter), large gaps (18.3 and 24.4m diameter), and a mesoscale wind disturbance treatment consisting of 0.4 and 1.2 ha shelterwoods. All treatments included multiple small deer exclosures to examine the impact of deer herbivory. Assessment of cover by herbaceous plants and seedlings indicated that overstory treatments had a larger effect on understory community composition than browsing by deer, whereas there was no effect of coarse wood levels. Species richness was highest in the small gap treatment and lowest in the control stands, possibly reflecting the increased dominance by a few ruderal and exotic species in treatments with increased canopy openness. Richness was also significantly lower inside exclosures than outside in some treatments, although browse-sensitive Trillium spp. were largely restricted to exclosures. Post-harvest seedling density increased with increasing overstory removal, with the mesoscale wind disturbance treatment containing the highest seedling density after three years. While browse protection generally did not have a significant effect on overall density of regeneration, several species, especially Betula alleghaniensis benefited from protection from deer browse. These initial results underscore the utility of natural disturbance-based treatments at increasing the complexity of second-growth communities and the importance of accounting for herbivory impacts on treatment responses.
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    Long-term Study of the Magney-Snively Old-Growth Northern Hardwood Forest, Duluth, Minnesota, USA
    (2022-06) Schimpf, David J; Kelly, Julia A
    Point-quarter measurements of trees and saplings made in a putatively old-growth Minnesota northern hardwood forest in 1961, 1980, and 2016 were analyzed by using plotless density-estimation methods, including a modified method that we developed. Stem densities of trees in 1980 and 2016 were higher than in 1961, and sapling stem density was much higher in 2016 than in each of the earlier years. Basal-area densities for both trees and trees-plus-saplings did not change significantly among years, but were higher for saplings in 2016 than in each of the other two years. Stem density and basal-area density of sugar maple increased in the tree stratum through time. The sugar maple tree population had a demographically stable size structure in each year. Sugar maple dominated the sapling stratum, increasing with time in relative densities and very strongly in absolute densities. Over the same time span yellow birch abundance declined in the tree stratum and mountain maple seemed to decline in the sapling stratum. Yellow birch mean individual size became larger with time. Basal-area densities estimated by the angle-gauge method in 2017 found standing-dead values to be about 8% of the live-stem values, with similar species compositions. Fallen large boles near the sample points in 2016 were more likely to be yellow birch than the large live trees were; in contrast, sugar maple was a smaller share of fallen large boles than of large live trees. Boles tended to have fallen toward the south, which did not match the directions in the record of strong wind gusts at Duluth International Airport. This old-growth ecosystem may hold at least 230 metric tons of organic carbon per hectare. Stem cores from red oaks showed little evidence of contamination from a steel mill that operated nearby prior to 1980, but have a somewhat elevated content of manganese. The Magney-Snively forest is an important complement to the other old-growth northern hardwoods remnants in the Lake Superior region, which differ from it by having a sizable representation of eastern hemlock.