Canadian vegetation response to climate and projected climatic change

• Main Author: Lenihan, James M.
• Other Authors: Frenkel, Robert E., Geosciences, Oregon State University. Graduate School
• Format: Doctoral or Postdoctoral Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Climatic changes > Canada > Mathematical models; Vegetation and climate > Canada > Mathematical models; Subarctic; Tundra
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/r207tt82f

The equilibrium response of Canadian vegetation to climate and climatic change was modeled at three organizational levels of the vegetation mosaic. The climatic parameters used as model drivers (i.e., snowpack, degree-days, minimum temperature, soil moisture deficit, and actual evapotranspiration) are components of climate that physiologically constrain the distribution of dominant plant life-forms and species in Canada. The rule-based Canadian Climate-Vegetation Model (CCVM) predicts the response of vegetation formations to climate. The rules define climatic thresholds across which one formation gives way to another. The CCVM simulation for current climatic conditions is more accurate and detailed than those of other equilibrium models. A series of ecological response surfaces predict the probability of dominance for eight boreal tree species in Canada with a high degree of success. Variation in the probability of dominance is related to the species' individualistic response to climatic constraints within different airmass regions. A boreal forest-type classification based on the probabilities of dominance shows a high degree of geographic correspondence with observed forest-types. Under two doubled-CO2 climatic scenarios, CCVM predicts a reduction in arctic tundra and subarctic woodland, a northward shift in the distribution of boreal evergreen forest and an expansion of temperate forest, boreal summergreen woodland, and two prairie formations. The response surfaces predict significant changes in species dominance under both climatic scenarios. Species exhibit an individualistic response to climatic change and respond differently under the different scenarios. All but one of the boreal forest-types derived from future probabilities of dominance are analogous to extant forest-types, but fewer types are distinguished. Geographic correspondence in the boreal forest regions simulated by the rule-based and response surface models under both the current and projected climates provides a link between the results of ...