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  • 1
    Electronic Resource
    Electronic Resource
    Brown's Woods: An Early Gravel Pit Forest Restoration Project, Ontario, Canada (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 4 (1996), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Few early examples of forest restoration projects are extant in the formerly forested parts of eastern North America. In this paper I present the history and status of an early forest restoration project in a denuded gravel pit in Ontario, Canada. The site was part of a deciduous forest until 1840, at which time forest clearing occurred. From 1874 to 1886 the site was exploited as a gravel pit. In 1887, under the direction of William Brown, it was planted with 14 species of coniferous and deciduous trees, of which 10 are still present. No soil preparation was carried out. The trees were pruned for 7 years, but in 1892 intensive maintenance ceased. In the 107 years since planting, the site has acquired some structural characteristics similar to the surrounding native deciduous forest, but it retains characteristics of an artificial community. Canopy cover has increased from 85% to over 95% since 1930 and is primarily Juglans nigra and Acer platan aides, Survivorship and current growth rates of native and exotic taxa have been similar. Recruitment patterns suggest that J. nigra and A. platanoides will dominate the canopy over the next century. The site is a useful example of the progress and problems created by attempts at forest restoration today.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.1996.tb00102.x
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental Restoration of Disturbed Cliff-Edge Forests in Bruce Peninsula National Park, Ontario, Canada (2003)
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 11 (2003), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Restoration of degraded natural vegetation in parks is often complicated by the need to maintain public access. We tested whether the natural canopy species, Thuja occidentalis, can be restored to degraded cliff edges in Bruce Peninsula National Park, Ontario, Canada without reductions in visitor numbers. Eighty 10-year-old and 80 4-year-old container-grown saplings and 1,400 seeds were planted and monitored for 4 years. Eight treatments were applied that tested for effects of planting site (distance from cliff edge and pathways) and supportive measures (soil, water, cages, or signs) on survival, growth, and damage. No trees became successfully established from seed. Younger trees showed faster initial establishment and growth, but 4-year survival was the same for both age groups (39%). Supplemental soil improved the health of planted trees, and both soil and water slightly improved their survival. Cages did not affect survival and growth but decreased damage to 4-year-old trees and increased it for 10-year-olds. Signs had no effect on any measured variable. Trees planted away from the cliff edge and from pathways had the greatest establishment success, 4-year survival, and general health. Relative visitor density, as estimated from spot counts of visitors, had the largest effect on restoration success; the results suggest a threshold of visitor density above which restoration may be impossible. Planting location, especially with respect to shade, was also important. The planting of 4-year-old trees without supportive measures is suggested as the most cost-effective restoration technique at this site. The results indicate that restoration of open woodland habitats is possible without total visitor exclusion but that some restrictions on visitor numbers or activities are necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1526-100X.2003.00140.x
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  • 3
    Electronic Resource
    Electronic Resource
    The impact of ten years at -20°C on gas exchange in five lichen species (1989)
    Springer
    Oecologia 78 (1989), S. 87-92 
    Details
    ISSN: 1432-1939
    Keywords: Frost resistance ; Freezing stress ; Lichen physiology ; Photosynthesis ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rates of net CO2 exchange in five sympatric species of Umbilicaria were measured after 10 years at-20°C. During that time, the lichens had been at either a high (saturated) or a low (air-dry) water content. The results showed an immediate, return to normal rates of gas exchange for air-dried then frozen U.vellea. Rates returned to normal for air-dried U. deusta within four days. The three other species studied, U. mammulata, U. papulosa and U. muhlenbergii showed intermediate responses. Water saturated then frozen thalli of U. vellea were irreparably damaged after 10 years; even fungal respiration was severely impaired. In U. mammulata, U. papulosa and U. muhlenbergii, photosynthesis was eliminated but fungal respiration rates were not influenced. In contrast to this, water saturated then frozen thalli of U. deusta showed a nearly equal photosynthetic capacity to the original rates following 10 years at -20°C. In all cases the magnitude of the effect of the long-term subzero treatment correlated well with the known distribution patterns of the lichens in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377201
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  • 4
    Electronic Resource
    Electronic Resource
    Seasonal changes in photosynthesis in the desiccation-tolerant fern Polypodium virginianum (1992)
    Springer
    Oecologia 89 (1992), S. 383-389 
    Details
    ISSN: 1432-1939
    Keywords: Polypodium virginianum ; Seasonal photosynthesis ; Desiccation tolerance ; Ferns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal changes in photosynthesis were examined in the desiccation-tolerant fern Polypodium virginianum growing in a forest understory along cliff edges of the Niagara Escarpment in southern Ontario, Canada. For plants growing in situ, the photosynthetic response to irradiance was examined on a seasonal basis, to determine the degree to which the utilization of light changed over the growing season. Experiments were executed on control plants, on previously desiccated then rehydrated plants, and on continuously hydrated plants to determine if prior desiccation influenced the response to light. Soil and xylem water potential and temperature were monitored and used as covariates in analyses. The results showed that carbon gain in the spring greatly exceeded that of any other season. Despite this, there was little change in the photosynthetic response to light on a seasonal basis even though plants were exposed to highly variable and highly limited light most of the time. Prior desiccation had a slight influence on photosynthetic rate but not on other photosynthetic parameters such as the light compensation point and Lhalf. Temperature was a significant seasonal covariate and additional experiments conducted in the laboratory showed that the response of photosynthesis to temperature was broad. Xylem water potential was correlated with seasonal changes in relative humidity. The results suggest that P. virginanum persists in hostile cliff-edge habitats by being able to exploit high-light periods in the spring and by thereafter maintaining a low but relatively constant rate of carbon despite prior exposure to fluctuating supplies of light and water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317416
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  • 5
    Electronic Resource
    Electronic Resource
    Habitat overlap/niche segregation in two Umbilicaria lichens: a possible mechanism (1984)
    Springer
    Oecologia 62 (1984), S. 118-125 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Umbilicaria muhlenbergii and Umbilicaria papulosa are two similar lichens which show extensive habitat overlap. Current theory predicts that for those resources that are limited, and of critical importance to both species, segregation is demand for or use of those resources ought to be present. Controlled experiments showed that the upper and lower cortical surfaces of the two species functioned in very different ways so that U. muhlenbergii is wetted most rapidly by runoff and mist-like precipitation whereas U. papulosa is wetted most rapidly by large raindrops. An analysis of the meteorological conditions in the natural habitat for the two lichens shows that the four months providing significant productivity in U. papulosa are the same months with a very high frequency of thunderstorms (which produce large drops). Conversely, the months which produce the greatest production in U. muhlenbergii are spread out over most of the year. When water is supplied after periods of dryness, the two species absorb it at different times and from different sources. This difference supports current ideas about niche segregation in plants but represents the first time it has been demonstrated for lichens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377384
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  • 6
    Electronic Resource
    Electronic Resource
    Photosynthetic response to sunflecks in the desiccation-tolerant fern Polypodium virginianum (1992)
    Springer
    Oecologia 89 (1992), S. 390-396 
    Details
    ISSN: 1432-1939
    Keywords: Polypodium virginianum ; Sunflecks ; In situ photosynthesis ; Desiccation tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The photosynthetic response to sunflecks was investigated in the fern Polypodium virginianum growing on cliff edges of the Niagara Escarpment, in southern Ontario, Canada. Ferns were exposed to natural precipitation, continuous watering, or continuous drought prior to exposure to artificial sunflecks. The results were analyzed using temperature, humidity and previous exposure to light as covariates. The response to sunflecks was extremely rapid and showed no measurable induction period in the field. Controlled experiments completed in the laboratory showed exceptionally short induction periods. Previous exposure to sunflecks, and desiccation did not influence the time constants of response to sunflecks although drying did reduce maximum rates of CO2 exchange. Polypodium virginianum shows an extremely rapid response to fluctuations in the supply of light, and this is interpreted to be advantageous to this species because of the array of extremely hostile conditions that occur at cliff edges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317417
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  • 7
    Electronic Resource
    Electronic Resource
    Early-spring gas exchange and uptake of deuterium-labelled water in the poikilohydric fernPolypodium virginianum (1993)
    Springer
    Oecologia 95 (1993), S. 9-13 
    Details
    ISSN: 1432-1939
    Keywords: Fern physiology ; Deuterium ; Water uptake ; Photosynthesis ; Leaf conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was carried out to determine if the desiccation-tolerant fernPolypodium virgimanum L. ecologically resembles lower plants by absorbing atmospheric water through its fronds and actively growing in early spring when the soil along cliff edges is still frozen. Three times between February and April, 1991,P. virginianum clonal mats were treated with deuterium-labelled water. Following each application, fronds were collected over several days and analyzed for the presence of deuterium. Two treatment groups plus a control were used: fronds were sprayed directly while covering the soil, or the roots were watered while protecting the fronds. The control mats were left untreated. Soil, air, and frond temperatures, plus photosynthesis and frond conductance were monitored throughout the study period. At subfreezing temperatures in February, no labelled water was taken up from the soil and no photosynthesis took place. Small amounts of label were absorbed from the soil in March during freeze-thaw cycles when rates of photosynthesis and stomatal conductance were both low. Large amounts of label were taken up from the soil in April when the soil was fully thawed and gas exchange was at normal seasonal levels. Label was not absorbed directly through the fronds when the plants were actively growing. Despite the desiccation tolerance ofP. virginianum, the timing and patterns of its water uptake and gas exchange in early spring resemble those found in higher vascular plants, not poikilohydric lower plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00649500
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  • 8
    Electronic Resource
    Electronic Resource
    Ancient stunted trees on cliffs (1999)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 398 (1999), S. 382-383 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] An undisturbed ancient woodland, dominated by tiny, slow-growing and widely spaced trees, grows on vertical cliffs of the Niagara escarpment in southern Canada. To investigate whether this woodland is unusual or is part of a previously undetected global pattern, we sampled ages and radial ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/18800
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  • 9
    Electronic Resource
    Electronic Resource
    Acclimation in arctic lichens (1975)
    [s.l.] : Nature Publishing Group
    Nature 254 (1975), S. 421-423 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Although there is increasing evidence of temperature acclimation of net assimilation rate (NAR) in various plants, both in the field1 3 and as responses induced under laboratory conditions45, investigations with higher plant systems are complicated by a combination of acclimatory response with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/254421b0
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  • 10
    Electronic Resource
    Electronic Resource
    Scale-dependent inconsistencies in the effects of trampling on a forest understory community (1993)
    Springer
    Environmental management 17 (1993), S. 239-248 
    Details
    ISSN: 1432-1009
    Keywords: Trampling disturbance ; Forest community composition ; Species richness ; Cliff ; Scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The response of forest understory vegetation to trampling applied at different temporal and spatial scales was determined in a cliff-edge forest in Ontario, Canada. Three frequencies (0, 50, 500 passes per year) of short-term trampling (one year) were applied to plots previously undisturbed. Existing trails that had received three frequencies (approx. 100, 500, 25,000 passes per year) of long-term trampling (18 years) were also studied. Community composition, species richness, and individual species frequency were recorded in plots within 4 m and (or) 1 m of the patch centerline. The quantitative and qualitative form of plant response to increased trampling was compared for short-term and long-term treatments, both within 4 m and within 1 m of the path centerline, to judge the consistency of trampling effects at different temporal and spatial scales. As trampling frequency increased, community composition changed progressively, but consistently, in plots both within 4 m and 1 m of the path centerline. Species richness was less affected by trampling and only decreased within 1 m of the path centerline at the highest level of trampling (25,000 passes per season for 18 years). Effects of trampling on individual species frequency were much less consistent at different temporal and spatial scales of trampling. The scale-dependence results suggest that field workers and resource managers both should try explicitly to include and define multiple scale components when trying to ascertain the response of vegetation to human disturbance factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02394693
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