The upward shift in altitude of pine mistletoe (Viscum album ssp. austriacum) in Switzerland—the result of climate warming?

Abstract

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.

Heat and drought 2003 in Europe: a climate synthesis

“…* Corresponding author: Rebetez@wsl.ch Climate change may affect the energy, water, and nutrient balance of forest ecosystems [10,25,29,35]. More frequent extreme meteorological events will leave trees chronically stressed [28] and possibly more vulnerable to secondary damages [14,36] like those caused by bark beetles [17].…”

Identification of Floral Relicts Based on Spatial Distance of Isolation

“…The choice of MAT as an effective temperature parameter is justifiable on the basis of recent results of studies using species distribution models (SDM) which show that averages play an important role in these phenomena, often more important than the extremes themselves [31][32][33]. Furthermore, as the distributions of most vascular plant species are nested in certain vegetation types (e.g., Mediterranean woodland, temperate deciduous broad-leaved forest, etc.…”

Faible différenciation génétique, à partir d'amplification aléatoire d'ADN polymorphe (RAPD), entre les types de pin sylvestre (Pinus sylvestrisL.) d'altitude et de plaine dans les Alpes à climat continental

“…Les premiers résultats de l'étude du dépérissement des pinèdes en Valais indiquent que l'affaiblissement des individus découle d'une association complexe de facteurs de stress comme la sécheresse [2,10], le gui (Viscum album ssp. austriacum) [11] et la concurrence [43,61] tandis que la mort résulte de l'action combinée de plusieurs agents pathogènes secondaires [43].…”

“…Il semblerait que le processus de dépérissement soit induit par l'action complexe de plusieurs facteurs de stress [43]. Les pé-riodes de sécheresse particulièrement intenses des dernières décennies seraient le facteur déclenchant [10,11,[42][43][44]. Ce type de dépérissement des pins ne se limite pas au Valais puisque d'autres régions alpines présentent des symptômes semblables, par exemple en Autriche ou au Val d'Aoste [6,58].…”