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Master of Science (MS)
Homann, Peter S.
Following dam removal on the Elwha River, WA, the ability of plants to access and uptake nutrients may be an important factor in ecosystem recovery. Foliage was collected in November 2014 from naturally-established black cottonwood (Populus trichocarpa) saplings growing in the dewatered Lake Aldwell reservoir sediments and adjacent forest. Analysis of variance was used to assess variability among reservoir sediment textures and the adjacent forest with respect to foliar macronutrient (N, P, K, Ca, Mg) and micronutrient (Fe, Mn, Zn, Cu, Ni) concentrations. Within the reservoir, foliar P, K, and Mn were higher, and foliar Ca was lower, in the fine sediments than in the coarse sediments. All reservoir environments had lower foliar Mg and Zn and higher foliar Mn than the adjacent forest. Correlation analyses indicated many significant correlations between nutrient pairs. Several positive nutrient correlations with N may indicate that N is stimulating protein synthesis, and several negative correlations between nutrient pairs may indicate that cations are competing for plant uptake. Considering seasonal nutrient fluctuation and senescence-induced nutrient resorption, foliar nutrient values measured in Lake Aldwell cottonwood were generally consistent with those reported in the literature from other populations of non-fertilized Populus. Exceptions were values for foliar Ca, Fe, and Cu, which were comparatively low. The majority of resorption-adjusted growing-season estimates for Lake Aldwell foliar macronutrients were within ranges reported as optimal in fertilized Populus, with the exception of high estimates for Mg in the adjacent forest and for N at all sites. Presently, black cottonwood productivity at Lake Aldwell does not seem to be constrained by nutrient limitation, but nutrient availability will be critical in determining species-compositional changes at dewatered Lake Aldwell and successional trajectories in other dewatered environments following dam removal.
Western Washington University
Elwha River (Wash.); Aldwell, Lake (Wash.)
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Citron, Ezra H., "Black Cottonwood (Populus Trichocarpa) Nutrition in the Dewatered Lake Aldwell Reservoir on the Elwha River, Washington" (2016). WWU Masters Thesis Collection. 466.