Silvicultural alternatives, competition regime and sensitivity to climate in a European beech forest

Growth variability, expressed by ring width sequences, was examined in an even-aged beech (Fagus sylvatica L.) forest in relation to stand structure, tree competition and climate. A competition-based growth model was developed to simulate stand dynamics and to calculate the yearly growth index series as a ratio between observed and predicted increments. Dendroclimatological analyses were used to evaluate the interactions between intraspecific competition and tree response to climate. For trees living at different competition levels, simple correlation coefficients were calculated between environmental variables (seasonal values of precipitation, temperature, water deficit and surplus) and the growth index series. Results show that beech response to temperature regime and water availability is significantly affected by competition level. When competition is strong, trees are highly sensitivity to water balance; whereas, at a low competition level, trees react positively to high temperatures. Considering that competition may affect tree sensitivity to climate and that thinnings can modify competition regimes it seems possible to influence the climate response of single trees and whole stands through silvicultural treatments and, consequently, to conduct forest management under a hypothesis of climate change. For this purpose, twenty thinning regimes were simulated with a single-tree growth model, varying the treatment intensity and frequency. Four representative regimes were analysed in detail, by examining the predicted yield and the distribution of trees in competition classes, and by evaluating stand sensitivity to climate change.