During the last decades the interest on mixed stands has increased in forestry due to their potential benefits, especially conifer-broadleaves mixtures. However, more knowledge is need about their dynamic and their response to silvicultural treatments. On the other hand, climate change can affect different species in different ways, so it is important to study the effect of climate in mixed stands with different silvicultures. In this work we present preliminary results of a thinning trial in a mixed stands of Pinus pinaster Ait. and Quercus pyrenaica Willd located in ?Montes de Toledo? (Central Spain). The main objectives of the experiment are to study the growth response of each species to thinning and to analyse if there are different climate-growth relationships between species and thinning treatments. The stand is a stratified mixture with a planted pine overstory and a natural regenerated oak lower stratum (understory). The experiment design is a Latin square of order three with the following treatments: heavy thinning from below (40% of basal area is removed), moderate thinning from below (25% of basal area is removed) and control or unthinned. The thinning was applied during the winter 2009-10. The position of all trees larger than 7.5 cm of diameter per plot was recorded. Diameter of all trees and heights of a sample were measured before the thinning. In each plot dendrometer bands were installed in 10 trees per species in order to study the effect of treatments on individual tree growth. Dedrometer bands were read every month to detect possible differences in growth pattern between treatments. These data were complemented with continued records registered with electronic dendrometer installed in one tree per species and treatment. Climatic variables and soil temperature and humidity were recorded with a weather station and soil sensors set up in the study site. Data from the first growing season after the thinning treatment (spring of 2010) will be presented in this work. The possible differences in total growth and in growth pattern between species and treatments will be analysed and discussed
