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UBC Theses and Dissertations

Stand development patterns as a consequence of the decline in Austrocedrus chilensis forests Amoroso, Mariano Martin


The forests of Austrocedrus chilensis (D.Don) Pic. Sern. et Bizarri in Argentina suffer decline and mortality throughout their natural distribution known as 'mal del ciprés'. While several aspects of this spatially unpredictable process of overstory tree mortality have been the focus of detailed studies, little attention has been committed to research on tree growth and stand dynamics in symptomatic forests or to examine stand development patterns and predict future stand structure. The aim of this thesis is to gain a better understanding of stand dynamics in A. chilensis forests experiencing tree mortality from 'mal del ciprés'. In order to achieve this goal, this thesis addressed three objectives: 1) to assess and study the temporal development of the radial growth decline at the tree and stand levels, 2) to evaluate the incidence of cambial mortality in living trees, and 3) to examine mortality patterns and their consequences for establishment of trees in the understory and growth of the surviving overstory trees. Tree death in symptomatic A. chilensis forests is preceded by a decline in radial growth. The occurrence of the decline is independent of the position of the trees in the canopy and unpredictable in time. A high proportion of sampled living trees, including healthy and symptomatic trees growing in subcanopy and canopy positions, exhibited partial cambial mortality of up to 39 years. Following the decline in radial growth, partial death of the cambium, and loss of crown vigour, the mortality of A. chilensis trees was unpredictable and variable in time among stands. While mortality of overstory trees has lead to the successful establishment of trees in the understory in all stands, the response of the residual overstory trees was variable. This thesis represents the first study to intensively explore the dynamics of A. chilensis forests affected by 'mal del ciprés'. Furthermore, this study is the first to examine the occurrence of radial growth decline and cambial mortality and discriminate the incidence among trees differentiated by tree health and the relative position in the canopy.

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