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Boulanger Yan Arseneault Dominique Boucher Yan Gauthier Sylvie Cyr Dominic Taylor Anthony R. Price David T. Dupuis Sébastien 《Landscape Ecology》2019,34(1):159-174
Landscape Ecology - Forest landscapes at the boreal–temperate ecotone have been extensively altered. Reducing the gap between current and presettlement forest conditions through... 相似文献
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Logging pattern and landscape changes over the last century at the boreal and deciduous forest transition in Eastern Canada 总被引：4，自引：0，他引：4
Forestry practices associated with the industrial era (since ~1900) have altered the natural disturbance regimes and greatly
impacted the world’s forests. We quantified twentieth century logging patterns and regional scale consequences in three sub-boreal
forest landscapes of Eastern Canada (117,000, 49,400 and 92,300 ha), comparing forestry maps depicting age and forest cover
types for early industrial (1930) and present-day (2000) conditions. Results were similar for the three landscapes, indicating
large-scale forest change during the twentieth century. In 1930, previous logging activities had been concentrated in the
lowlands and along the main hydrographical network, as compared to a more even distribution over the landscapes in 2000, reflecting
a decreasing influence of the environmental constraints on forest harvesting. In 1930, old-aged forests (>100 years) accounted
for more than 75% of the unlogged areas of the three landscapes, as compared to less than 15% for the present-day conditions.
Logging practices have thus inverted the stand age distribution of the landscapes that are currently dominated by young and
regenerating stands. The 1930 forest cover types showed a clear relationship with elevation, with conifers located in the
lowlands and mixed and deciduous stands restricted to the upper slopes. Between 1930 and 2000, 58–64% of the conifer areas
transformed to mixed and deciduous forests, such that no clear altitudinal relationships remained in 2000. We conclude that
twentieth century logging practices have strongly altered the preindustrial vegetation patterns in our study area, to the
point that ecosystem-based management strategies should be developed to restore conifer dominance, altitudinal gradients,
as well as the irregular structure inspired from old forest stands. 相似文献
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Over the last two centuries, logging has caused major, but unquantified, compositional and structural changes in the southern portion of the North American boreal forest. In this study, we used a series of old forest inventory maps coupled with a new dendrochronological approach for analyzing timber floating histories in order to document the long-term transformation (1820–2000) of a southern boreal landscape (117 000 ha) in eastern Quebec, Canada, in response to logging practices. Landscape exploitation became increasingly severe throughout this time period. During the ninetieth century (1820–1900) of limited industrial capacity, selective logging targeted pine and spruce trees and excluded balsam fir, a much abundant species of the forest landscape. Logging intensity increased during the first half of the twentieth century, and targeted all conifer species including balsam fir. After 1975, dramatic changes occurred over the landscape in relation to clear-cutting practices, plantations, and salvage logging, which promoted the proliferation of regenerating areas and extensive plantations of the previously uncommon black spruce. Overall, logging disturbance resulted in an inversion in the forest matrix, from conifer to mixed and deciduous, and from old to regenerating stands, thus creating significant consequences on forest sustainability. If biodiversity conservation and sustainable forestry are to be management goals in such a heavily exploited forested landscape, then restoration strategies should be implemented in order to stop the divergence of the forests from their preindustrial conditions. 相似文献
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Context
Knowledge of how environmental gradients generate changes in community composition across forest landscapes (β-diversity) represents a critical issue in the era of global change, which exerts especially powerful impacts by shifting disturbance regimes.Objectives
We analyzed the response of tree communities to increased disturbance rates that were linked to European settlement at the temperate-boreal interface of eastern Canada. We tested whether disturbance has led to spatial homogenization or heterogenization, and to decoupling or strengthening of community-environment relationships.Methods
We used a reconstruction of pre-industrial tree communities based on historical land survey records (1854–1935), together with modern data, to assess changes in tree β-diversity patterns. Then, β-diversity was partitioned into fractions explained by spatial (dbMEM) and environmental variables (latitude, elevation, slope, drainage and surface deposits) in order to assess changes in spatial structures and community-environment relationships.Results
In pre-industrial times, environmental variables explained only a small proportion of β-diversity since dominant taxa were present across the range of environmental gradients, whereas habitat specialists were very rare. Between pre-industrial and modern times, our analysis highlights an increase in β-diversity and the proportion of β-diversity that was explained by environmental variables. Increased disturbance rates have favored early-successional habitat specialist taxa and reduced the habitat breadth of pre-industrial generalists, thereby increasing the strength of community-environment relationships.Conclusions
Our results support that disturbance can alter the strength of community-environment relationships and also suggest that functional traits of species within the regional pool could predict whether or not disturbance alters such relationships.5.
Singh M Arseneault M Sanderson T Murthy V Ramassamy C 《Journal of agricultural and food chemistry》2008,56(13):4855-4873
Polyphenols are the most abundant antioxidants in diet. Indeed, fruits, vegetables, beverages (tea, wine, juices), plants, and some herbs are loaded with powerful antioxidant polyphenols. Despite their wide distribution, research on human health benefits truly began in the mid-1990s (Scalbert, A.; Johnson, I. T.; Saltmarsh, M. Am. J. Clin. Nutr. 2005, 81, S15S-217S). Phenolic compounds have been receiving increasing interest from consumers and manufacturers because numerous epidemiological studies have suggested associations between consumption of polyphenol-rich foods or beverages and the prevention of certain chronic diseases such as cancers and cardiovascular diseases (Manach, C.; Mazur, A.; Scalbert, A. Curr. Opin. Lipidol. 2005, 16, 77-84; Duthie, S. J. Mol. Nutr. Food Res. 2007, 51, 665-674). Furthermore, in the past 10 years, research on the neuroprotective effects of dietary polyphenols has developed considerably. These compounds are able to protect neuronal cells in various in vivo and in vitro models through different intracellular targets (Ramassamy, C. Eur. J. Pharmacol. 2006, 545, 51-64). However, it is not at all clear whether these compounds reach the brain in sufficient concentrations and in a biologically active form to exert beneficial effects. On the other hand, it has become clear that the mechanisms of action of these polyphenols go beyond their antioxidant activity and the attenuation of oxidative stress. Therefore, there is a need for more research on their intracellular and molecular targets as special pathways underlying distinct polyphenol-induced neuroprotection. The focus of this review is aimed at presenting the role of some polyphenols from fruits, vegetables, and beverages in neuroprotection and particularly in Alzheimer's disease and the research challenges in this area. 相似文献
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