Regional changes of Pinus pinaster site index in Spain using a climate-based dominant height model

Abstract

This study compares two site index estimations for Mediterranean maritime pine ( Pinus pinaster Ait.) stands in the Iberian Peninsula. The first prediction was performed under the assumption of constant climate conditions, whereas the second one used foreseen climate according to an energy-use increment and high population growth (IPCC’s A2 emission scenario). We used an existing climate-based dominant height model that incorporates temperature, seasonal precipitation in winter and autumn, and drought length as driver variables for dominant height growth. Climate attributes were retrieved from eight regional climate models nested in the same atmospheric–ocean global circulation model. Forest stand data from 188 experimental plots in four natural regions were used to compare regional climate change trends. Results indicated a climate-related diminishing trend of site index values, although some regional differences were evident. In the northern stands, the negative effects were not observed, and in some cases, forest productivity increased on low site index classes. Conversely, in the southernmost stands, there is a significant decrease in the site index across all productivity classes. Western and eastern stands also showed a decreasing trend but to a lesser extent. Our results confirm the vulnerability of stands to warmer and drier climate conditions in the southern Mediterranean region in relation to wood productivity.