THE EFFECTS OF GLOBAL CLIMATE CHANGE ON LANDSCAPE EVOLUTION IN THE BOREAL FOREST OF THE CENTRAL ALASKA RANGE

Glaciation cycles during the Quaternary produced major shifts in vegetation patterns in subarctic regions. Predicted rapid changes in global climate at high latitudes could produce vegetative shifts not previously recognized during the Quaternary. Global climate change could specifically affect the subarctic region by shifting the boreal forest biome north, which could alter ecological and geomorphic processes particularly exhibited in landscape evolution. To investigate hillslope processes operating in the boreal forest environment and how this may vary between glacial and interglacial cycles, we target the extensive sequence of fluvial terraces along the Nenana River valley in Alaska.

We hypothesize that factors causing higher soil shear strength such as depth to permafrost, slope angle, slope aspect, rooting depth, and soil moisture content act as primary controls on diffusion rates at higher-latitudes. Limited existing age control, coupled with correlation to the Marine Isotope Stages (MIS), are being used to date the fluvial terrace sequence of the Nenana River valley and derive a nonlinear sediment flux equation for this boreal forest environment. Preliminary observations suggest that high-latitude hillslopes diffuse at slower rates and appear younger than they are when compared to arid, mid-latitude regions. This behavior and resultant appearance is due to controlling factors which heighten soil shear strength. This diffusion characteristic is exemplified in our study area by hillslope profiles transitioning from a convex to concave shape through an inflection point which migrates over time.

In conclusion, diffusion rates are slower in this boreal forest environment when compared to mid-latitude regions, which makes landforms appear younger than their true age. Changes in global climate could cause shifts in vegetation, increasing diffusion rates at high latitudes not previously noted in the Quaternary. An increased rate of diffusion could not only shift the boreal forest biome north, but potentially increase hazards related to land failure and have global implications at this latitude.