Relationship between heartwood radius and early radial growth, tree age, and climate in Pinus canariensis

Abstract

Heartwood radius at breast height was studied in 31 sampling sites from natural stands of Canary Islands pine (Pinus canariensis Chr. Sm. ex DC) covering the natural range of the species. After withdrawal of defective and nonheartwood samples, 1640 sound radial cores ranging in age from 30 to 265 years were analysed. Linearized models for the prediction of heartwood radius at breast height were obtained using stepwise regression methods. The best fit was attained including age and early radial growth variables (radius of the 25 or to the 50 inner rings), while stem radius inside bark and whole radial growth rate did not improve the prediction. Sampling sites were classified into five climate types, established according to the main plant communities associated with Pinus canariensis. The use of separate models for each climate type led to a significant reduction of the residual variance compared with multiple climate models. This confirmed that climate is an essential factor in heartwood development in Pinus canariensis even when 51–73% of heartwood radius variation is explained by age and early growth. For fixed values of age and early growth, models predicted wider heartwood in drier climate types than in wet and high-altitude (supra-nubius) climate types.