Connections of Geomorphological Activity, Geological History and Organic Carbon Storage in Steep, Mountainous Drainage Basins: A Field Investigation

This study investigates connections amongst geomorphological activity, geological history and organic carbon storage for trees, shrubs and herbs along valley floors of channel networks in small, steep drainage basins in the Canadian Rockies. The amount of potential storage space for organic carbon often varies considerably along valley floors in mountainous terrain due to variability in valley floor widths resulting from large-scale tectonic controls. Vegetation density on valley floors is anticipated to show significant variability along channel networks in steep terrain due to changing environmental conditions (e.g., climate, moisture, geomorphic disturbances). Valley floor widths were measured and analyzed for two steep drainage basins, Ribbon Creek and Porcupine Creek, in the Front Ranges of the Canadian Rockies. Results show that the complex tectonic history and associated geological structures and bedrock type influence valley floors widths, with no regular, discernible pattern in an upstream direction. Field surveys were undertaken to document vegetation density along these same channel networks. Geomorphological processes, such as debris flows and other mass wasting events, influence grain sizes along valley floors in the study drainage basins. Substrate characteristics, such as grain size, were found to influence vegetation density along channel networks. Finally, total organic carbon storage along valley floors is determined for Ribbon Creek and Porcupine Creek. Values of total organic carbon storage are influenced by the joint controls of potential storage space for organic carbon that results from the tectonic history and the control of geomorphological activity on substate conditions and vegetation density.