Impact of Drought on the Intra-Annual Growth of Pinus sylvestris L

Climatic scenarios for the Mediterranean Region forecast increasing frequency and intensity of drought events. We analyzed how Pinus sylvestris modifies its cambial phenology and intra-annual growth under enhanced drought conditions. For this purpose, a rainfall exclusion experiment was applied in 2012 to trees located in the lower elevation limit of a mountain forest in Central Spain. Preliminary results show a significantly longer growing season in small trees than in big trees, regardless of the treatment. The tracheid enlargement period was longer in control trees than in trees subjected to rainfall exclusion regardless the size class. Cambial activity and gas exchange rates of Pinus sylvestris responded immediately to drier conditions, which could indicate vulnerability to drought enhancement. Stronger differences between treatments are expected for the second year of the experiment due to the cumulative effect of drought in the rainfall exclusion plots.