Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Physical Sciences and Mathematics
Hillslope Asymmetry Maps Reveal Widespread, Multi-Scale Organization, Michael J. Poulos, Jennifer L. Pierce, Alejandro N. Flores, Shawn G. Benner
Hillslope Asymmetry Maps Reveal Widespread, Multi-Scale Organization, Michael J. Poulos, Jennifer L. Pierce, Alejandro N. Flores, Shawn G. Benner
Geosciences Faculty Publications and Presentations
Hillslope asymmetry is the condition in which oppositely-facing hillslopes within an area have differing average slope angles, and indicates aspect-related variability in hillslope evolution. As such, the presence, orientation and magnitude of asymmetry may be a useful diagnostic for understanding process dominance. We present a new method for quantifying and mapping the spatial distribution of hillslope asymmetry across large areas. Resulting maps for the American Cordillera of the Western Hemisphere and the western United States reveal that hillslope asymmetry is widespread, with distinct trends at continental to drainage scales. Spatial patterns of asymmetry correlate with latitude along the American Cordillera, …
Late Holocene Relationships Among Fire, Climate, And Vegetation In Rangeland Ecosystems Of Southwestern Idaho, Nathan A. Nelson, Jennifer Pierce
Late Holocene Relationships Among Fire, Climate, And Vegetation In Rangeland Ecosystems Of Southwestern Idaho, Nathan A. Nelson, Jennifer Pierce
Geosciences Faculty Publications and Presentations
Rangelands are characterized by more arid climates than forested regions; therefore, establishing fire histories using traditional methods (e.g. fire-scars from trees or charcoal in lake sediments) is problematic. This study uses radiocarbon dating of charcoal preserved in alluvial fans and stream deposits to reconstruct a record of fire and geomorphic response in rangelands of southwestern Idaho. Samples indicate three primary periods of fire-related activity: 4400 – 4000, 2000 – 1400, and 650-400 cal yr BP. Charcoal macrofossil identification and comparison with other regional climate and fire records indicate this area has likely switched between a "fuel-limited" system (fires limited by …
Arctic Landscapes In Transition: Responses To Thawing Permafrost, James P. Mcnamara
Arctic Landscapes In Transition: Responses To Thawing Permafrost, James P. Mcnamara
Geosciences Faculty Publications and Presentations
Observations indicate that over the past several decades, geomorphic processes in the Arctic have been changing or intensifying. Coastal erosion, which currently supplies most of the sediment and carbon to the Arctic Ocean [Rachold et al., 2000], may have doubled since 1955 [Mars and Houseknecht, 2007]. Further inland, expansion of channel networks [Toniolo et al., 2009] and increased river bank erosion [Costard et al., 2007] have been attributed to warming. Lakes, ponds, and wetlands appear to be more dynamic, growing in some areas, shrinking in others, and changing distribution across lowland regions …
Hyporheic Exchange And Water Chemistry Of Two Arctic Tundra Streams Of Contrasting Geomorphology, Morgan J. Greenwald, William B. Bowden, Michael N. Gooseff, Jay P. Zarnetske, James P. Mcnamara, John H. Bradford, Troy R. Brosten
Hyporheic Exchange And Water Chemistry Of Two Arctic Tundra Streams Of Contrasting Geomorphology, Morgan J. Greenwald, William B. Bowden, Michael N. Gooseff, Jay P. Zarnetske, James P. Mcnamara, John H. Bradford, Troy R. Brosten
Geosciences Faculty Publications and Presentations
The North Slope of Alaska’s Brooks Range is underlain by continuous permafrost, but an active layer of thawed sediments develops at the tundra surface and beneath streambeds during the summer, facilitating hyporheic exchange. Our goal was to understand how active layer extent and stream geomorphology influence hyporheic exchange and nutrient chemistry. We studied two arctic tundra streams of contrasting geomorphology: a high-gradient, alluvial stream with riffle-pool sequences and a low-gradient, peat-bottomed stream with large deep pools connected by deep runs. Hyporheic exchange occurred to ~50 cm beneath the alluvial streambed and to only ~15 cm beneath the peat streambed. The …