Local-Scale Drivers of Spatial Patterns and Demographic Rates of Conifer Species in a Forest Chronosequence in Coastal British Columbia

• Author / Creator

  Schurmann, Kaitlyn D.

• Growth, mortality and recruitment are the fundamental demographic processes driving changes in forest structure and dynamics. Rapid changes observed in many forests globally have imposed serious threats to ecosystem services such as carbon sequestration, biodiversity and hydrology, emphasizing the importance of understanding the underlying mechanisms. In this thesis, I collected spatial and inventory data from five 1-hectare forest plots in a chronosequence on southern Vancouver Island, B.C. I used spatial point pattern analysis and regression modeling to determine the effects of competition and climate on tree spatial patterns and demographic rates of Douglas fir, western hemlock and western redcedar over a 17-year census period. Douglas fir growth and mortality were strongly influenced by negative density-dependent (competition) processes in all plots of the chronosequence with the species becoming more regularly distributed in older stands. Western hemlock and western redcedar growth was negatively influenced by competition, while facilitative processes may promote tree survival of these two shade-tolerant species in most stands. Recruitment of all three species occurred most often in close proximity to adult trees. Growth of the study species was also driven by tree size and climate. Summer precipitation was the most important climate variable, negatively affecting growth for all study species. Other temperature and precipitation variables were significant for the focal species, but the direction of the growth response was not consistent. Species-specific responses to climate highlight the difficultly in predicting stand-level changes under altered climate regimes. The results of this study underscore the importance of competition and climate in driving forest structure and dynamics in all ages of stands, necessitating the inclusion of both sets of variables in analyzing demographic rates. Knowledge of competition and climate as drivers of forest dynamics and structure can be incorporated into forestry and conservation management decision-making, and findings from this study provide a better understanding of the processes driving dynamics of forest succession, and can be used for anticipating stand structure in the future.

• Subjects / Keywords

  • Density dependence
  • Spatial patterns
  • Forest demographics
  • Competition
  • Chronosequence
  • Douglas fir
  • Climate
  • Western hemlock
  • Western redcedar

• Graduation date

  Spring 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3222RJ5M

• 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.