Vignette d'image

Rebetez, Martine

Nom
Rebetez, Martine
Affiliation principale
Site web
Fonction
Professeure ordinaire
Email
martine.rebetez@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/403
_
0000-0002-3337-2025

Résultat de la recherche

Filtres

4
31
4
Réinitialiser les filtres

Paramètres

Voici les éléments 1 - 4 sur 4
  • Publication
    Métadonnées seulement
    The upward shift in altitude of pine mistletoe (Viscum album ssp austriacum) in Switzerland - the result of climate warming?
    (2005)
    Dobbertin, Matthias
    ;
    Hilker, Nadine
    ;
    Rebetez, Martine 
    ;
    Zimmermann, Niklaus E
    ;
    Wohlgemuth, Thomas
    ;
    Rigling, Andreas
    Pine mistletoe (Viscum album ssp. austriacum) is common in natural Scots pine (Pinus sylvestris L.) forests in the alpine Rhone Valley, Switzerland. This semi-parasite, which is regarded as an indicator species for temperature, increases the drought stress on trees and may contribute to the observed pine decline in the region. We recorded mistletoes on representative plots of the Swiss National Forest Inventory ranging from 450 to 1,550 m a.s.l. We found mistletoe on 37% of the trees and on 56% of all plots. Trees infested with mistletoe had a significantly higher mortality rate than non-infested trees. We compared the current mistletoe occurrence with records from a survey in 1910. The current upper limit, 1,250 m, is roughly 200 m above the limit of 1,000-1,100 m found in the earlier survey 100 years ago. Applying a spatial model to meteorological data we obtained monthly mean temperatures for all sites. In a logistic regression mean winter temperature, pine proportion and geographic exposition significantly explained mistletoe occurrence. Using mean monthly January and July temperatures for 1961-1990, we calculated Skre's plant respiration equivalent (RE) and regressed it against elevation to obtain the RE value at the current mistletoe elevation limit. We used this RE value and temperature from 1870-1899 in the regression and found the past elevation limit to be at 1,060 m, agreeing with the 1910 survey. For the predicted temperature rise by 2030, the limit for mistletoe would increase above 1,600 m altitude.
  • Publication
    Accès libre
    Climate change may already threaten Scots pine stands in the Swiss Alps
    (2004)
    Rebetez, Martine 
    ;
    Dobbertin, Matthias
    Large numbers of Scots pine are dying in the dry inner-alpine valleys of the European Alps; in Switzerland, locally almost half the Scots pine (Pinus sylvestris L.) population has died since 1995. As Switzerland's temperature has increased at more than twice the global average in the 20(th) stop century and as most of this increase has occurred during the last 20 years, we investigated possible relationships between the dying Scots pine and climatic parameters. We centred our studies in the upper Rhone valley. Our results show that the strong climatic warming that has occurred in recent years may well be the indirect cause of the mortality observed in these forests. Tree mortality was highest following the dry and hot year 1998, and tree defoliation, an indicator of tree vitality, showed a strong correlation with the previous year's precipitation. While precipitation showed no clear significant trend over time, the number of warm days (mean >20degreesC, maximum >25 degreesC) and potential evapotranspiration have significantly increased over the last 20 years. Higher temperatures favour pine wood nematodes and bark beetles, both of which are found at the study site, and increasing drought stress reduces tree resistance against pathogens. As these forests have in part protective functions, there is a need to better understand the mortality through interdisciplinary research and also to find means to change the species composition in order to establish tree species that are better able to withstand warmer temperatures.
  • Publication
    Accès libre
    Regionalization of precipitation in Switzerland by means of principal component analysis
    (1997)
    Baeriswyl, Pierre-Alain
    ;
    Rebetez, Martine 
    The technique of principal component analysis and of cluster analysis has been applied to two sets of precipitation data in Switzerland, one containing 47 stations (1961-80), and the other 101 stations (1981-1993), with the aim of understanding more fully the spatial distribution of precipitation regimes. Seven regions were highlighted in the first case and 13 in the second. The high spatial coherence which appeared is quite remarkable and confirms the usefulness of these techniques for the analysis of the spatial distribution of meteorological variables, even in a topographically complex area such as Switzerland. The two regional distributions obtained not only correspond fairly well to the large, well-known physical regions of Switzerland, but also go much further, separating the Swiss Plateau into 3 clearly differentiated regions, for example. Regional distributions such as those discussed here can have value for climate change issues, and in particular numerical modeling of climate or climate change impacts on forests.
  • Publication
    Accès libre
    An analysis of regional climate-change in Switzerland
    (1994)
    Beniston, Martin
    ;
    Rebetez, Martine 
    ;
    Giorgi, F
    ;
    Marinucci, M
    An analysis of daily climatological data covering the period from 1901 to 1992 for four locations in Switzerland (Zurich, Lugano, Davos, and Santis) has been made. The study has highlighted the fact that climate change this century is characterized by increases in minimum temperatures of about 2K, a more modest increase in maximum temperatures (in some instances a decrease of maxima in the latter part of the record), little trend in the precipitation data, and a general decrease of sunshine duration through to the mid 1980s. The interannual variability is generally large, and filtering of the data to remove high-frequency noise shows that the regional climate undergoes a series of fluctuations of between 8 and 20 years' duration. The temperature change over this century is of greater magnitude than the global temperature changes published in the literature, reflecting an amplification of the global signal in the Alpine region; warming has been most intense in the 1940s, followed by the 1980s; the cooling which intervened from the 1950s to the late 1970s was not sufficient to offset the warming in the middle of the century. Pressure statistics have been compiled as a means of providing a link between the regional-scale climatological variables and the synoptic, supra-regional scale. These statistics show that pressure also exhibits a number of decadal-scale fluctuations, with the appearance of a new and anomalous behavior in the 1980s; in this decade, pressure reaches annual average values far higher than at other times this century. The pressure field is well correlated with the North Atlantic Oscillation (NAO) Index for distinct periods of the record (1931-1950 and 1971-1990) and is almost decorrelated from the NAO Index for the other decades of the century; this is indicative of transition from one climatic regime to another, dominated by zonal flow when the correlation with the NAO Index is high. In the 1980s, when zonal flow over the North Atlantic is strong, episodes of persistent, anomalously high pressures (blocking highs) are seen to occur over Switzerland, particularly during the winter season. The difference between the zonal and non-zonal regimes is particularly marked between the decade of the 1950s and that of the 1980s. The impact of this change between the 1950s and the 1980s on a number of climatological variables has been investigated statistically in order to provide an illustration of the manner in which changes in synoptic regimes (i.e., 'climate change') impacts upon climate characteristics on a regional scale. The analysis shows that temperature, precipitation, snow depth, and sunshine duration are indeed sensitive to large-scale influences; not only can yearly mean changes be quantified, but also seasonal and monthly fluctuations.