Crown size and growing space requirement of common tree species inurban centres, parks, and forests

Abstract

Tree crown size determines among others tree’s growth, carbon sequestration, shading, filtering of fineair particulates, and risk of wind-breaking. The dependence of crown size on species, resource supply,and tree age complicates an accurate evaluation of a tree’s space requirement, and its size-dependentfunctions and services in urban as well as in forested areas.Based on a world-wide dataset of tree crown measurements of 22 common urban tree species we firstderived species-specific crown radius–stem diameter relationships for open grown conditions. By clusteranalysis we then assigned the 22 species to 5 crown extension types and developed mean relationshipsof tree height, crown radius, crown projection area, and crown volume depending on tree diameter foreach type. This allometric analysis yielded auxiliary relationships which can be used for estimating thespecies-specific crown size and dynamics at a given tree dimension. We discuss how the results cansupport the choice and initial spacing of particular species and the assessment and prognosis of theirfunctions and services.