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Human impacts on fire occurrence: a case study of hundred years of forest fires in a dry alpine valley in Switzerland 总被引:2,自引:1,他引:1
Thomas Zumbrunnen Patricia Menéndez Harald Bugmann Marco Conedera Urs Gimmi Matthias Bürgi 《Regional Environmental Change》2012,12(4):935-949
Forest fire regimes are sensitive to alterations of climate, fuel load, and ignition sources. We investigated the impact of human activities and climate on fire occurrence in a dry continental valley of the Swiss Alps (Valais) by relating fire occurrence to population and road density, biomass removal by livestock grazing and wood harvest, temperature and precipitation in two distinct periods (1904–1955 and 1956–2006) using generalized additive modeling. This study provides evidence for the role played by humans and temperature in shaping fire occurrence. The existence of ignition sources promotes fire occurrence to a certain extent only; for example, high road density tends to be related to fewer fires. Changes in forest uses within the study region seem to be particularly important. Fire occurrence appears to have been negatively associated with livestock pasturing in the forest and wood harvesting, in particular during the period 1904–1955. This study illustrates consistently how fire occurrence has been influenced by land use and socioeconomic conditions. It also suggests that there is no straightforward linear relationship between human factors and fire occurrence. 相似文献
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Numerous analyses of the possible impacts of future climatic changes on tree species composition have been published for
both lowland and high-elevation forests. Most of these studies were based on the application of forest "gap" models, and the
vast majority of them considered only changes in the average of climatic parameters over time. In this study, we use a unique
data set on reconstructed past climatic variations to analyse forest dynamics simulated by the forest gap model ForClim. This
analysis forms the basis for a systematic exploration of the ecological effects of changing means vs. changing variability
of climate on central European forests. A reconstruction of historical climate covering the last 470 years in the Swiss lowlands
(ClimIndex) is extrapolated to a transect across the alpine (cold) treeline and used to simulate the influence of climate
variations on the time scale of decades on forest biomass and tree species composition at both sites. While the simulation
at the low-elevation site shows little sensitivity to climate variations, the results from upper subalpine forests suggest
that two major dieback events would have occurred at elevations above the current but below the climatic tree line, induced
by clusters of exceptionally cold summers. The results are in agreement with available dendrochronological data and with documentary
evidence on massive negative impacts on flora and fauna at high elevations during these periods. We conclude that ForClim
is capable of capturing the effects on tree population dynamics of climate variability at these sites as reconstructed from
the ClimIndex record. A factorial design is used to address the sensitivity of ForClim to changes of the long-term averages
vs. changes of the variability of monthly temperature and precipitation data. To this end, the simulated tree species composition
of near-natural forests is examined along a climate gradient in Europe. The results indicate that there are three types of
forest response: (1) little sensitivity to both kinds of change, (2) strong sensitivity to changes in the means, but little
sensitivity to changing variability, and (3) strong sensitivity to changing variability at least in parts of the examined
climate space. Half of the cases investigated fall under the third category, suggesting that emphasis should be placed on
also assessing the sensitivity of ecosystems to future changes in climate variability rather than on changes of average values
alone.
Electronic Publication 相似文献
14.
Harald Sverdrup Salim Belyazid Bengt Nihlgård Lars Ericson 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):163-179
The ForSAFE model, designed for modelling biogeochemical cycles (water, acidity, base cation, nitrogen and carbon) in terrestrial
ecosystems, was modified with a vegetation response module (VEG), incorporating the effects of: nitrogen pollution, acidification,
soil moisture, temperature, wind chill exposure, light and shading by trees, grazing by animals, competition between plants,
above ground for light and below ground for water and nutrients. The model calculates the response of number ground vegetation
plant groups. The integrated model was tested and validated at integrated level II forest monitoring sites across Sweden,
four have been shown here, and used to assess the effect of acidification and nitrogen pollution in relation to factors such
as climate change, forest management and changing grazing pressure. The response functions have been derived from single-factor
experiments and integrated through the model structure for use on whole systems. The tests with the model suggest that the
ground vegetation composition is reasonably well predicted, that much research remains before the model is fully tested and
operational, and that the model may serve as a tool for assessing impacts of climate change, acid rain and forest management
on plant biodiversity in forested areas. 相似文献
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Harald Schaaf 《Umweltwissenschaften und Schadstoff-Forschung》2007,19(1):63-68
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