60-year record of stem xylem anatomy and related hydraulic modification under increased summer drought in ring- and diffuse-porous temperate broad-leaved tree species

Abstract

Key message: By combining dendrochronological time-series analysis with radial vessel features, we show that the reconstruction of hydraulic properties improves our understanding of tree species’ acclimation potential to climate change. Abstract: The vascular architecture plays a crucial role in the productivity and drought tolerance of broadleaf trees, but it is not yet fully understood how the hydraulic system is acclimating to a warmer and drier climate. Because vessel features may record temporal and spatial variability in climatic signals of the past better than tree-ring width, we combined dendrochronological time-series analysis with the calculation of stem hydraulic properties derived from radial vessel features. We aimed to reconstruct the development and sensitivity of the hydraulic system over six decades and to identify climatic control of xylem anatomy for five co-existing broad-leaved diffuse- and ring-porous tree species (genera Acer, Fagus, Fraxinus and Quercus) across three sites covering a precipitation gradient from 548 to 793 mm. We observed a significant influence of the climatic water balance (CWB) on the vessel features of all species, but the time lag, magnitude and direction of the response was highly species-specific. All diffuse-porous species suffered a decline in vessel diameter in dry years, and increase in vessel density in dry years and the year following. However, F. sylvatica was the only species with a significant long-term change in anatomical traits and a significant reduction in potential hydraulic conductivity (Kp) after dry winters and in dry summers, accompanied with the largest long-term decline in tree-ring width and the largest growth reduction in and after years with a more negative CWB. In contrast, the comparison across the precipitation gradient did not reveal any significant vessel-climate relationships. Our results revealed considerable plasticity in the hydraulic system especially of F. sylvatica, but also evidence of the drought-sensitivity of this species in accordance with earlier dendroecological and physiological studies. We conclude that the long-term reconstruction of hydraulic properties can add substantially to the understanding of the acclimation potential of different tree species to climate change.