Growth dynamics of Mediterranean woodlands under climate change: a dendroecological approach in southwest Iberia [Póster]

Abstract

Recently, vegetation in the Iberian Peninsula has exhibited global-change- type processes including species distribution shifts, altered plant phenology and enhanced forest decline and tree mortality. Studies based on long-term data sets, like tree rings, are providing evidences about the implication of climate change in these mechanisms. Dendrochronology is the science of dating tree rings. The term “dendroecology” refers to applications of dendrochronological techniques to obtain the information content of dated rings for studying dynamics in forest ecology and environment. Based on tree rings from 2 Quercus ilex L. and 7 Pinus pinea L. stands, we examined stand dynamics and sensitivity to climate in southwest Iberian Peninsula through dendroecological methods. In this presentation we summarize the results of these investigations and highlight common patterns in growth response to climate change. The climate in the study region is Mediterranean. Meteorological register and climate indices describe increasing temperatures and more frequent extreme events, i.e. heavy rainfalls and heat waves, since the mid-1970s. The studied ecosystems differ in stand structure and silviculture (oak open-woodlands with silvo-pastoral use, closed-canopy pine stands for dune ecosystem conservation, timber and nut production), age (oaks are older than 100 years, pines vary from 70 to 150 year-old), soils (Arenosols, Cambisols, Regosols, Planosols and Luvisols in the pine stands; Regosols, Leptosols, Cambisols, Acrisols, Alisols and Lixisols in the oak stands), altitude and distance from the coast (oaks are at 170-200 m a.s.l. inland and pine stands are distributed from the coastline, 0-10 m a.s.l., to the inland, 250 m a.s.l.). The oak ecosystems were affected by massive tree mortality while pines showed no evident sign of weakening. Tree-ring width chronologies revealed growth suppressions coinciding with increasing drought. To extract the climatic signal, prewithened residual chronologies were calculated from biweight means of ratios between tree-ring widths and individual cubic splines. A common dendroclimatic signal was found in the 1 st principal component of the residual chronologies. Moreover, a common response to changing climate over the last decades was indicated by increasing growth synchrony (i.e. intercorrelation among residual chronologies), enhanced sensitivity to climate (i.e. year-to- year growth variability) and similar temporal changes in climate-growth correlations (i.e. enhanced response to winter precipitation, lower correlation with late-spring/early summer precipitation, increasing sensitivity to high temperatures). These studies constitute the first application of dendroecology to growth dynamics in Southwest Iberian Mediterranean forests and provide an assessment of the adaptive capacity and vulnerability of these populations to changing growing conditions.