Models for Forest Growth and Mortality: Linking Demography to Competition and Climate

  • Author / Creator
    Dawson, Andria E
  • The Earth’s forests are of great economic, ecological, and social importance, and sustaining them is paramount for mitigating climate change. To successfully sus- tain forests we must understand their internal demographic dynamics and their relationship to climate. In this thesis, I developed methods for investigating forest dynamics and understanding their relationship to climate. I applied these methods to data from the Alberta boreal forest and the oak forests of the Eastern United States. First, dendrochronological methods were used to develop a retrospective data set from the Alberta mixedwood boreal. This data was used to estimate white spruce mortality and construct mortality models based on either recent growth or competition. Both models classify dead or live spruce with 75% accuracy, indi- cating the potential of using more easily available competition data. Second, I developed a quantitative approach for predicting Alberta mixedwood demogra- phy as a function of tree size and competition predictors using a size-structured integral projection model (IPM). Two models were defined, one with competitive structure, and one without. Model projections were tested using independent data, and results show that the IPM with competitive structure better predicts annual size distribution. Implementation of the IPM presents technical challenges: IPMs must be numerically discretized, and the choice of integration scheme may lead to accuracy or efficiency loss. I analyzed several quadrature schemes for representa- tive IPMs in the third part of the thesis. Results show that the midpoint method is often sufficient, but an Adjusted Gauss-Legendre method leads to higher accuracy. In the final part of the thesis I considered how climate is related to annual growth of chestnut oak in the the Eastern United States. Previously, trees growing in closed-canopy forests were not thought to produce ring-widths useable in climate reconstruction. However, by employing more advanced mathematical tools I used a network of oak forests to identify a strong enough precipitation signal to extend the current meteorological record back 150 years. My thesis illustrates the im- portance of careful model formulation, implementation and validation in resolving climate and competition effects in forest dynamics.

  • Subjects / Keywords
  • Graduation date
    Fall 2013
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.