Architecture of Iberian canopy tree species in relation to wood density, shade tolerance and climate

Lourens Poorter,Miguel A Zavala,Mariano Moreno-De Las Heras,Elena Lianes

doi:10.1007/s11258-012-0032-6

Abstract

Tree architecture has important consequences for tree performance as it determines resource capture, mechanical stability and dominance over competitors. We analyzed architectural relationships between stem and crown dimensions for 13 dominant Iberian canopy tree species belonging to the Pinaceae (six Pinus species) and Fagaceae (six Quercus species and Fagus sylvatica) and related these architectural traits to wood density, shade tolerance and climatic factors. Fagaceae had, compared with Pinaceae, denser wood, saplings with wider crowns and adults with larger maximal crown size but smaller maximal height. In combination, these traits enhance light acquisition and persistence in shaded environments; thus, contributing to their shade tolerance. Pinaceae species, in contrast, had low-density wood, allocate more resources to the formation of the central trunk rather than to branches and attained taller maximal heights, allowing them to grow rapidly in height and compete for light following disturbances; thus, contributing to their high light requirements. Wood density had a strong relationship with tree architecture, with dense-wooded species having smaller maximum height and wider crowns, probably because of cheaper expansion costs for producing biomechanically stable branches. Species from arid environments had shorter stems and shallower crowns for a given stem diameter, probably to reduce hydraulic path length and assure water transport. Wood density is an important correlate of variation in tree architecture between species and the two dominant families, with potentially large implications for their resource foraging strategies and successional dynamics.

Highlights

Tree architecture refers to the overall shape of the tree, and has important consequences for the performance of species and individuals, as it determines resource capture, mechanical stability and dominance over competitors (Kohyama 1987; King et al 2006)
Wood density plays a central role in the life history variation of tree species as low-density wood is cheap to construct, allowing for rapid growth in stem dimensions, whereas highdensity wood allows for a high survival rate and long lifespan (Loehle 1988; Poorter 2008; King et al 2006)
This study focuses on continental Iberia, which shows a large range of different climates and provides an ideal setting to test whether Iberian tree species are adapted to the climate in which they occur, and whether they show different allometries

Summary

Introduction

Tree architecture refers to the overall shape of the tree, and has important consequences for the performance of species and individuals, as it determines resource capture, mechanical stability and dominance over competitors (Kohyama 1987; King et al 2006). A number of studies have emphasized the relationship between tree architecture and wood material properties such as wood density. This variable is closely related to the resistance to wood to rupture and self-loading (van Gelder et al 2006; Chave et al 2009), and to the production of stable horizontal branches, resistance to external forces, and mechanical stability. In evergreen broadleaved tropical forests, for example, do shade-tolerant species have denser wood (van Gelder et al 2006), for temperate forest the relationship is sometimes less clear, for example, many coniferous species are very shade tolerant, but they tend to have a low wood density because of the lack of fibre in their wood

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Discussion

Conclusion