Plasticity in Dendroclimatic Response across the Distribution Range of Aleppo Pine (Pinus halepensis)

Abstract

We investigated the variability of the climate-growth relationship of Aleppo pine across its distribution range in the Mediterranean Basin. We constructed a network of tree-ring index chronologies from 63 sites across the region. Correlation function analysis identified the relationships of tree-ring index to climate factors for each site. We also estimated the dominant climatic gradients of the region using principal component analysis of monthly, seasonal, and annual mean temperature and total precipitation from 1,068 climatic gridpoints. Variation in ring width index was primarily related to precipitation and secondarily to temperature. However, we found that the dendroclimatic relationship depended on the position of the site along the climatic gradient. In the southern part of the distribution range, where temperature was generally higher and precipitation lower than the regional average, reduced growth was also associated with warm and dry conditions. In the northern part, where the average temperature was lower and the precipitation more abundant than the regional average, reduced growth was associated with cool conditions. Thus, our study highlights the substantial plasticity of Aleppo pine in response to different climatic conditions. These results do not resolve the source of response variability as being due to either genetic variation in provenance, to phenotypic plasticity, or a combination of factors. However, as current growth responses to inter-annual climate variability vary spatially across existing climate gradients, future climate-growth relationships will also likely be determined by differential adaptation and/or acclimation responses to spatial climatic variation. The contribution of local adaptation and/or phenotypic plasticity across populations to the persistence of species under global warming could be decisive for prediction of climate change impacts across populations. In this sense, a more complex forest dynamics modeling approach that includes the contribution of genetic variation and phenotypic plasticity can improve the reliability of the ecological inferences derived from the climate-growth relationships.

Consistent limitation of growth by high temperature and low precipitation from range core to southern edge of European beech indicates widespread vulnerability to changing climate

“…4). This result is similar to those reported by de Luis et al (2013), who showed that the growth of Pinus halepensis in drier and warmer regions was more sensitive to mean annual temperature. Our results for F. sylvatica therefore show that trees growing in climatically marginal regions (rather than geographically marginal regions) are more sensitive to climate.…”

“…3 and Appendix S6). In summary, significant correlations between RWI and summer temperature (negative) and summer precipitation (positive), both considered indicators of a drought limitation on growth, did not show strong geographical patterns observed in some previous studies (Chen et al 2010;de Luis et al 2013), particularly for summer temperature. This was despite the strong environmental gradients found across our study area (Fig.…”

“…One of the fundamental principles of dendroecology and dendroclimatology is that tree populations in marginal regions are more sensitive to climate than those in core regions, with more interannual variability in growth and stronger relationships between growth and limiting climate factors, particularly summer drought (Fritts 1966). This principle has been demonstrated for conifers (Carrer et al 2010;de Luis et al 2013;Linares et al 2009) and also to a more limited extent in broadleaved species such as F. sylvatica, although research has focused on elevation transects or regional networks of sites. For example, studies have shown that F. sylvatica at low elevations is more sensitive to summer drought than at high elevations (Di Filippo et al 2007;Hartl-Meier et al 2014).…”

“…across its distribution in western North America, showing that southern populations were better adapted to drought than their northern counterparts. de Luis et al (2013) showed that populations at the southern distribution edge of Pinus halepensis Miller were more strongly limited by drought than populations from north of the Mediterranean, although they showed that southern subpopulations varied in their drought limitation of growth. The results of these studies, which indicate complex and species-specific geographical variations in the response of growth to climate, support the results of provenance trials, which have consistently reported that different subpopulations have different genetic adaptations to climate (e.g.…”

Tree-ring-based drought reconstruction in the Iberian Range (east of Spain) since 1694

“…A similar metric was considered by Levanic et al (2013) in Eastern Europe where the August SPI integrating 3 preceding months was reconstructed. In general, similar responses to late summer precipitation and annual precipitation were detected for other species in the Mediterranean basin (Touchan et al 2007;Martin-Benito et al 2010;de Luis et al 2013).…”