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Title: Growing timber trees with straight stems : an exploration of relationships between morphological traits in some broadleaved tree species
Author: Cowell, Anthony Michael
Awarding Body: De Montfort University
Current Institution: De Montfort University
Date of Award: 2004
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The research described here had two novel aims: first, to assess the morphological characteristics of the regrowth, in particular stem straightness, of juvenile broadleaved trees following coppicing; and second, to investigate why some trees have straight stems and others do not. These questions were investigated by carrying out a series of field experiments in a range of species, age classes and locations. Coppicing produced rapid regrowth from the stump sprouts of juvenile oak (Quercus robur) and sweet chestnut (Castanea sativa). Multi-stemming and mortality were not significant. Height regrowth was almost three times faster than the height growth in the uncoppiced trees in the first year following coppicing. Thereafter vigour in the coppice trees declined. After five years there was little difference between the height of the coppiced trees and the height of the uncoppiced trees. The regrowth of the coppiced trees was much straighter than the uncoppiced trees. Branch length was also reduced as a result of coppicing. The improvements in stem straightness declined gradually but after five years the coppiced trees were still significantly straighter than the uncoppiced trees. This is a novel approach to inducing stem straightness in young trees without the need for close spacing. The coppice experiments suggested that stem straightness was related to branch length. A series of investigations were carried out in juvenile populations of oak, sweet chestnut, ash (Fraxinus e.xcelsior) and sycamore (Acer pseudoplatanus) to explore relationships between morphological characteristics. The work was extended to semi mature and mature populations of broadleaved trees of various species. Branch length, tree height and stem straightness were found to be related in all species, age classes and locations. The morphological characteristics of the trees in the study were proportional to one another. Trees with symmetrical crowns had straighter stems than those with asymmetrical crowns. In trees with asymmetrical crowns those with proportionately shorter branches had straighter stems than trees with long branches. In effect, crown symmetry is the most important single factor that is related to stem straightness in trees. When trees do not have symmetrical crowns, branch length is the most important factor that is related to stem straightness. Finally, a new and practical method of ranking stem quality, based on branch length and stem straightness is presented. Broadleaved trees with straight stems follow rules of proportionality. This is an original insight into the nature of tree growth.
Supervisor: Not available Sponsor: De Montfort University School of Agriculture
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available