Lodgepole Pine and Interior Spruce Radial Growth Response to Climate and Topography in the Southern Rocky Mountains, Alberta

Abstract

As climate change continues to alter forest ecosystems, it is important to understand the details of how trees respond to climatic conditions across the landscape. Climate change may have spatially variable impacts on radial growth of tree species growing in mountainous environments, making generalizing across broad spatial scales inappropriate from a forest management perspective. In Alberta, understanding the growth response of lodgepole pine (Pinus contorta) and interior spruce (Picea glauca x Picea engelmannii hybrid) to climate and topographic variables will assist in understanding how these species may be affected by future changes in climate. Radial growth-climate response of trees in mountainous landscapes (e.g. the Rocky Mountains) may be altered at fine scales by topography and are often unstable through time (i.e. ‘divergence problem’). Because of this, it is important to consider topographic variables when spatially and temporally analyzing tree radial growth response to climate in subalpine communities. Currently, there is knowledge of how trees respond to climate at regional scales, but less is known about how trees interact with climate and topography at the catchment scale. This thesis addresses these topo-climatic relationships in the front range of the Rocky Mountains, Alberta, with particular focus on lodgepole pine and interior spruce growth response to monthly climate (total monthly precipitation and average monthly temperatures), aspect, slope, elevation, soil depth, and topographic wetness index (TWI). Results suggest species-specific and site-specific spatiotemporally diverse radial growth responses to climate and topography, indicating that future climate change is likely to have highly spatially variable impacts on tree radial growth response in mountainous environments. Keywords: lodgepole pine (Pinus contorta), interior spruce (Picea glauca; Picea engelmannii), dendroclimatology, topography, climate change, biogeography