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Spatial and temporal patterns of dust emissions in semi-arid landscapes, southeastern Utah, USA 2008-2011

Flagg, Cody Benjamin

Titre : Spatial and temporal patterns of dust emissions in semi-arid landscapes, southeastern Utah, USA 2008-2011

Auteur : Flagg, Cody Benjamin

Université de soutenance : UNIVERSITY OF COLORADO AT BOULDER

Grade : Master of Science (MS) 2012

Aeolian dust can influence nutrient availability, soil fertility, plant interactions, and water-holding capacity in both source and downwind environments. Measuring dust emission and deposition can reveal spatial and temporal patterns of dust flux, informing various ecological and atmospheric models, as well as advancing understanding of aeolian dust processes. Quantifying controls, flux rates, and locating sources of dust is particularly important to regional-scale environmental dynamics, as dust from the Colorado Plateau has recently been linked to changes in the hydrology and nutrient cycling of the San Juan Mountains. Vegetation, ground cover, land-use, and climate patterns affect dust generation in different ways. Previous studies have documented the effects of these variables on dust flux in dryland settings of the western United States, but very few have identified sources, flux rates, and controls on the Colorado Plateau. This study integrates dust emission, ecological, and climate data collected over three years to elucidate spatial and temporal patterns of dust flux from the eastern Colorado Plateau in southeastern Utah. A network of 108 passive sediment collectors spanning numerous types of ecosystems, soil types, land-use histories, and geologic settings covering approximately 4000 square kilometers across southeastern Utah was used to sample horizontal sediment emissions. The sample archive dates to early 2008 and is currently the largest known record of field-scale dust emissions for the southwestern United States. Samples were collected every four months from the sediment collectors at heights of 15 cm up to one meter. Line transects were established at each collection site to measure vegetation cover, collect soil samples, and estimate surface-soil stability. Dust flux peaked during the spring months in all plant-community types, related to higher, sustained surface wind speeds that begin in the early spring. Dust flux was lowest during the winter period when surface wind speeds are typically low. Contrary to other studies on dust emissions, antecedent precipitation one, two, and three seasons prior to sample collection did not significantly influence emission rates. Flux rates also did not vary significantly among soil types. Sites dominated by shrubs and/or non-native plants had higher flux rates compared to grasslands, woodlands, and sites with high biological soil-crust cover. Physical factors controlling dust emissions were complex and varied from one vegetation type to another. Vegetation type, seasonal wind patterns, and certain physical site characteristics are important factors in controlling dust emission rates in southeastern Utah.


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