Climatic responses of tree-ring width and δ13C signatures of sessile oak (Quercus petraea Liebl.) on soils with contrasting water supply

We investigated climate-growth relationships (in terms of tree-ring width, basal area increment (BAI), and tree-ring delta C-13 signatures) of Quercus petraea in Central Europe (Luxembourg). Tree responses were assessed for 160 years and compared for sites with contrasting water supply (i.e. Cambisols vs. Regosols with 175 and 42 mm available water capacity, respectively). Oak trees displayed very low climate sensitivity, and climatic variables explained only 24 and 21 % of variance in tree-ring width (TRW) (Cambisol and Regosol sites, respectively). Contrary to our expectations, site-related differences in growth responses (i.e. BAI, delta C-13 signatures) to climate shifts were not significant. This finding suggests a high plasticity of oak trees in the study area. Despite a distinct growth depression found for all trees in the decade 1988-1997 (attributable to increasing annual mean temperatures by 1.1 A degrees C), oak trees completely recovered in subsequent years. This indicates a high resilience of sessile oak to climate change. Shifts in delta C-13(corr) signatures were mainly affected by temperature, and peaks in delta C-13(corr) values (corrected for the anthropogenic increase in atmospheric CO2) coincided with decadal maximum temperatures. Correlations between delta C-13 signatures and TRW (mainly affected by precipitation) were not significant. This finding suggests that wood growth often was disconnected from carbon assimilation (e.g. due to carbon storage in the trunk or allocation to seeds). Since the selection of drought-resistant tree species gains importance within the context of adaptive forest management strategies, Q. petraea proves to be an adaptive tree species in Central Europe's forests under shifting climatic conditions.