e-journal
Common allometric response of open-grown leader shoots to tree height in co-occurring deciduous broadleaved trees
Background and Aims Morphology of crown shoots changes with tree height. The height of forest trees is
usually correlated with the light environment and this makes it difficult to separate the effects of tree size and of light conditions on the morphological plasticity of crown shoots. This paper addresses the tree-height dependence of shoot traits under full-light conditions where a tree crown is not shaded by other crowns.
Methods Focus is given to relationships between tree height and top-shoot traits, which include the shoot’s leafblades and non-leafy mass, its total leaf-blade area and the length and basal diameter of the shoot’s stem. We examine the allometric characteristics of open-grown current-year leader shoots at the tops of forest tree crowns up to 24 m high and quantify their responses to tree height in 13 co-occurring deciduous hardwood species in a cool-temperate forest in northern Japan.
Key Results Dry mass allocated to leaf blades in a leader shoot increased with tree height in all 13 species. Specific leaf area decreased with tree height. Stem basal area was almost proportional to total leaf area in a leader shoot, where the proportionality constant did not depend on tree height, irrespective of species. Stem length for a given stem diameter decreased with tree height.
Conclusions In the 13 species observed, height-dependent changes in allometry of leader shoots were convergent. This finding suggests that there is a common functional constraint in tree-height development. Under fulllight conditions, leader shoots of tall trees naturally experience more severe water stress than those of short trees. We hypothesize that the height dependence of shoot allometry detected reflects an integrated response to heightassociated water stress, which contributes to successful crown expansion and height gain.
Key words: Allometry, current-year leader shoot, hierarchical Bayesian model, pipe model, tree height, water stress.
Tidak ada salinan data
Tidak tersedia versi lain