Influence of tree density on climate-growth relationships in a Pinus pinaster Ait. forest in the northern mountains of Sardinia (Italy)

Abstract

Abstract: In view of the projected increases in the frequency and duration of drought events in the Mediterranean basin, a better understanding how differences in stand structure influence climate-growth relationships can improve and drive the conservation and management strategies for marginal forests in mountain areas. In this study, we examined the intra-annual variability of growth patterns and responses to climate of two maritime pine (Pinus pinaster Ait.) stands growing at contrasting tree densities at low elevation in northern Sardinia. A dendroclimatic analysis was used to assess the climate-growth relationships of these trees on monthly, seasonal and annual scales. The late spring and summer precipitations of the current year appeared to be the crucial climatic driver that encouraged the radial growth of the species in this mountain stand. However, summer drought was the primary climate constraint, exerting negative effects on P. pinaster growth. Summer Palmer drought severity index showed contrasting influence on latewood growth responses to drought conditions related to stand density, remaining significant also during the autumn months in the stand with the highest tree density. Our findings indicate that stands growing at high tree densities may experience more prolonged water shortages, especially during the late summer and early autumn months. Additionally, since the early 1980s, as precipitation has decreased, the influence of previous rainy years on radial growth has been highly significant in the stand with the lowest tree density. This result might suggests that these trees are able to utilize a greater amount of water reaching deeper soil horizons stored due to the previous rainy years, especially during periods of low precipitation.