Has global change induced divergent trends in radial growth of Pinus sylvestris and Pinus halepensis at their bioclimatic limit? The example of the Sainte-Baume forest (south-east France)

Abstract

Abstract• It is agreed that climate (precipitation and temperature) influences the distribution of plant species. Near the margins of a species' natural range, climate becomes limiting to physiological processes. There, climate change may be expected to have a significant impact on tree growth and the species' ranges may be altered.• In order to assess what influence climate change could exert on the distribution of pine species at their margin, radial growth trends in ring-width chronologies over the last century were analysed. In the French Mediterranean area where climate change is characterized by increased temperature, forest plots were selected along an altitudinal transect on the north-facing slope of the Sainte-Baume mountain (Bouches-du-Rhône, France) where the ranges of Pinus sylvestris and Pinus halepensis overlap.• Two growth patterns were identified. For P. halepensis, radial growth has increased at all altitudes indicating that climate change has improved growth conditions of this species near the margin of its ecological range. For P. sylvestris, radial growth has increased only at low altitudes and even decreased at high altitudes.• It must be deduced that the growth changes observed cannot be generalised either at the species level or at the geographical level and must be interpreted with great caution. Mots-clés :changement global / limite bioclimatique / croissance radiale / Pinus halepensis / Pinus sylvestris Résumé -Les changements globaux ont-ils induit des tendances de croissance radiale opposées chez Pinus sylvestris et Pinus halepensis à leur limite bioclimatique ? L'exemple de la forêt de la Sainte-Baume.• Il est admis que les facteurs climatiques (températures et précipitations) sont en partie responsables de la distribution des espèces en limitant leurs processus physiologiques en limite de distribution d'aire. Dans ce cas, les conséquences des changements climatiques sur la croissance sont susceptibles d'y être le plus marqué et leurs distributions pourraient varier.• Afin d'évaluer les conséquences des changements climatiques, les tendances de croissance observées au siècle dernier dans les séries temporelles de cernes ont été analysées. En zone médi-terranéenne française, où les changements climatiques sont caractérisés par une augmentation des températures, des placettes ont été sélectionnées selon un gradient altitudinal sur le flanc nord de la montagne de la Sainte-Baume (Bouches-du-Rhône, France) où les distributions de Pinus sylvestris et Pinus halepensis se superposent.• Deux patrons de croissance ont été identifiés. La croissance radiale de P. halepensis a augmenté quelle que soit l'altitude considérée indiquant que le changement climatique a amélioré les conditions de croissance de l'espèce à sa limite de distribution. Chez P. sylvestris, des tendances de croissance opposées inattendues ont été mises en évidence : la croissance a augmenté à faible altitude et a diminué aux altitudes les plus élevées.• Il en résulte que les changements de croissance observés ne peuvent être ...

Response of Pinus sylvestris L. to recent climatic events in the French Mediterranean region

“…5), rule out using this parameter individually or including it in a small group with the previous or following months. In previous studies at the same sites, May rainfall and temperature were considered as key parameters for Scots pine radial growth (Vila et al 2008). Nevertheless, groups of climate parameters selected by PLS regression can be considered as representative of five ecologically critical periods:…”

“…In a previous study on Scots pine located at Sainte-Baume mountain, Vila et al (2008) evidenced strong long-term trends regarding radial growth over the period 1900-2000. To better understand the growth pattern and potential response of this species to climate change, it was necessary to complete the previous study with several new, complementary parameters, and to analyze the impact of recent extreme climatic events.…”

Black pine (Pinus nigra Arn.) growth divergence along a latitudinal gradient in Western Mediterranean mountains

“…Around the Mediterranean basin, some studies show decreasing radial growth trends for different tree species during the second half of the 20th century (Macias et al, 2006;Piovesan et al, 2008;Sarris et al, 2007) while others show growth enhancement during the same period (Martínez-Vilalta et al, 2008;Touchan et al, 2005;Vila et al, 2008). For example, in north-eastern Spain Scots pine (Pinus sylvestris L.) shows positive growth trends mainly on wetter sites (Martínez-Vilalta et al, 2008) whereas in France the opposite is true for both Aleppo (Pinus halepensis Mill.)…”

“…For example, in north-eastern Spain Scots pine (Pinus sylvestris L.) shows positive growth trends mainly on wetter sites (Martínez-Vilalta et al, 2008) whereas in France the opposite is true for both Aleppo (Pinus halepensis Mill.) and Scots pines (Vila et al, 2008).…”

Climate Change Impact on Tree Architectural Development and Leaf Area

“…They usually conclude that tree radial growth is affected by continuous changes in climatic conditions (trends) and by strong climatic events [3,26,52]. Height growth was more occasionally used as indicator due to time-consuming measurements in the field, but gave reliable results [53].…”