Winter precipitation effect in a mid-latitude temperature-limited environment: the case of common juniper at high elevation in the Alps

Abstract

Common juniper (Juniperus communis L.) is by far the most widespread conifer in the world. However, tree-ring research dealing with this species is still scarce, mainly due to the difficulty in crossdating associated with the irregular stem shape with strip-bark growth form in older individuals and the high number of missing and wedging rings. Given that many different species of the same genus have been successfully used in tree-ring investigations and proved to be reliable climate proxies, this study aims to (i) test the possibility to successfully apply dendrochronological techniques on common juniper growing above the treeline and (ii) verify the climate sensitivity of the species with special regard to winter precipitation, a climatic factor that generally does not affect tree-ring growth in all Alpine high-elevation tree species. Almost 90 samples have been collected in three sites in the central and eastern Alps, all between 2100 and 2400 m in elevation. Despite cross-dating difficulties, we were able to build a reliable chronology for each site, each spanning over 200 years. Climate-growth relationships computed over the last century highlight that juniper growth is mainly controlled by the amount of winter precipitation. The high variability of the climate-growth associations among sites, corresponds well to the low spatial dependence of this meteorological factor. Fairly long chronologies and the presence of a significant precipitation signal open up the possibility to reconstruct past winter precipitation.

Diverging shrub and tree growth from the Polar to the Mediterranean biomes across the European continent

“…Previous investigations across the Siberian subarctic, including some of our Polar study sites, detected a post-1960s divergence between tree growth and summer temperatures which was explained by a delayed snow melt due to increasing winter precipitation (Vaganov et al, 1999). Similar detrimental effect of snow pack duration on growth has been described for prostrate junipers in the Alps (Pellizzari et al, 2014). Similar detrimental effect of snow pack duration on growth has been described for prostrate junipers in the Alps (Pellizzari et al, 2014).…”

“…In the case of junipers, we chose a spline function with a 50% frequency cut-off at 100 years; in this way, we removed the long-term biological growth trend, maintaining high (annual)-to midfrequency (multidecadal) growth variability resulting in dimensionless ring-width indices (Helama et al, 2004). Tree chronologies were similarly detrended to remove the typical age-related trend of declining ring-width (often absent in junipers; see Pellizzari et al, 2014) using firstly a negative exponential curve and then applying a 100-year-long spline. Finally, with both growth forms, junipers and trees, the first-order autocorrelation of the standardized ring-width indices was removed through autoregressive modelling.…”

“…communities (Pellizzari et al, 2014). ), spruce (Picea abies Karst) and stone pine (Pinus cembra L.) forests and shrubby (Juniperus communis L., Rhododendron spp., Salix spp.)…”

“…Contrastingly, in low-stature and prostrate shrubs, meristems are more coupled to ground microclimate conditions, which are usually warmer with respect to free atmospheric conditions due to the reduction of heat exchange (K€ orner, 2012b). However, the insulating benefits of snow pack to shrub meristems may also be detrimental whether the snow pack is so thick or dense to induce a delayed snow melting and a shortening of the growing season (Pellizzari et al, 2014). In addition, during winter shrub, meristems are often covered and protected by snow, limiting the risk of freezing and mechanical damages as compared to tree buds (Bokhorst et al, 2009;Rixen et al, 2010).…”

Up to 400‐year‐old Rhododendron shrubs on the southeastern Tibetan Plateau: prospects for shrub‐based dendrochronology

“…Srur & Villalba 2009; Garc ıa-Cervig on Morales et al 2012;Gazol & Camarero 2012;Liang et al 2012Liang et al , 2015Schweingruber et al 2013). To date, only a few long (>150 years) shrub ring-width chronologies have been developed to the best of our knowledge (see Hallinger et al 2010;Weijers et al 2010;Boulanger-Lapointe et al 2014;Pellizzari et al 2014;Myers-Smith et al 2015).…”