RESPONSE TO CLIMATE OF TREE RINGS AND VESSEL FEATURES IN ILEX AQUIFOLIUM L. FROM DIFFERENT STANDS

The analysis of time series of tree ring anatomical features is a successful approach to understand the effect of environmental factors on tree growth and thus constitutes a valuable source of information about environmental conditions. Ilex aquifolium L. (Aquifoliaceae) is an evergreen species of wide distribution in Europe, however poorly investigated in the ecological studies. Our objectives were: (i) to compare ring dimension and vessel features in Ilex aquifolium L.; (ii) to determine the degree of association of these variables with interannual variations in climate; and (iii) to quantify the usefulness of developing continuous vessel series in dendroecological studies. The study was performed on Ilex aquifolium L. trees from two different sites: Monte San Giorgio (Switzerland) and Monte Pollino (Southern Italy). Twenty wood samples were collected, sectioned and stained according to usual wood anatomy techniques. Measuring procedure combined wood preparation and digital image techniques achieving a very efficient measurement of diffuse-porous ring vessels. Owing to the semi-automatic routine evaluation, an investigation on large datasets was possible, making them stronger for our aims. Vessels were traced in sequential sections, and vessel networks were reconstructed. Chronologies of tree-ring width (TRW), mean vessel area (MVA) and other wood anato - mical parameters were developed and relationship with climate data was assessed, for the period 1925-2012, using correlations and response functions. To assess differences in wood formation among sites, a PCA was also performed based on TRW and MVA per site. Patterns of wood formation differed between the two sites. In addition, all vessel features were intrinsically linked to ring width. Our main results suggested that vessel features contain environmental information pretty similar to those stored in TRW.