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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

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  • 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.