The influence of multiple scales of environmental context on the distribution and interaction of an invasive seagrass and its native congener / Michael P. Hannam.
Material type:
TextPublication details: Seattle: University of Washington, 2013.Description: ix, 109 pages : illustrations (chiefly color), maps ; 28 cmSubject(s): Genre/Form: Online resources: Dissertation note: Dissertation (Doctor of Philosophy, School of Environmental and Forest Sciences)--University of Washington, 2013. Abstract: Predicting invasive species impacts is complicated by the variable context in which they occur. Furthermore, species invasion is an inherently multi-scale process, warranting examination at multiple spatial scales. In its introduced range, the invasive seagrass Zostera japonica often grows at higher elevations than its native congener, Zostera marina, but at some sites the congeners overlap. At overlapping sites, the two seagrasses often grow in a patch mosaic associated with intertidal microtopography. I examine the role of multiple scales of environmental context in the vertical zonation of Z. japonica and Z. marina, and the relationship of meter to decameter scale microtopography to the local distribution and biotic interactions of Z. marina and Z. japonica. Nearshore intertidal topography, hydrodynamic exposure, and tidal range were examined as abiotic predictors of the deep extents of Z. japonica and Z. marina, the shallow extent of Z. marina and the elevation overlap of the two species, both at within site and among site spatial scales. Bottom profile complexity was the most consistently important predictor studied, confirming the importance of the geomorphic template on the zonation of these species. Z. japonica's deep extent was well-predicted by Z. marina's shallow extent, but Z. marina's shallow extent was best predicted by physical factors. Using a terrestrial laser scanner, I mapped and monitored a one hectare study site for three years. The location and shape of microtopographic features were generally stable from year to year, but the magnitude of local relief was variable. Z. marina was more likely to occur in water-filled depressions than on well-drained mounds, but the presence of Z. japonica, was better predicted by low shoot densities of Z. marina. Transplant experiments revealed that Z. marina suppressed Z. japonica shoot densities, more so in pools than on mounds. Topographic context remained the most influential predictor of Z. marina responses, even when I transplanted Z. marina into higher densities of Z. japonica. I show that decameter to kilometer-scale environmental context influences the vertical zonation of Z. marina and Z. japonica, and that meter to decimeter-scale microtopographic relief influences their local spatial distribution. Furthermore, centimeter-scale topographic relief can modify competitive outcomes and promote decameter-scale coexistence of these two species.
| Item type | Current library | Call number | Status | Notes | Date due | Barcode | Item holds | |
|---|---|---|---|---|---|---|---|---|
| Non-lending Thesis | Elisabeth C. Miller Library Thesis - Compact Shelving | THESIS HANNAM 2013 (Browse shelf(Opens below)) | Not for loan | Faculty advisors: Kern Ewing, Sandy Wyllie-Echeverria, L. Monika Moskal. | 39352800153959 |
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Vita.
Dissertation (Doctor of Philosophy, School of Environmental and Forest Sciences)--University of Washington, 2013.
Includes bibliographical references (pages 86-99).
Predicting invasive species impacts is complicated by the variable context in which they occur. Furthermore, species invasion is an inherently multi-scale process, warranting examination at multiple spatial scales. In its introduced range, the invasive seagrass Zostera japonica often grows at higher elevations than its native congener, Zostera marina, but at some sites the congeners overlap. At overlapping sites, the two seagrasses often grow in a patch mosaic associated with intertidal microtopography. I examine the role of multiple scales of environmental context in the vertical zonation of Z. japonica and Z. marina, and the relationship of meter to decameter scale microtopography to the local distribution and biotic interactions of Z. marina and Z. japonica. Nearshore intertidal topography, hydrodynamic exposure, and tidal range were examined as abiotic predictors of the deep extents of Z. japonica and Z. marina, the shallow extent of Z. marina and the elevation overlap of the two species, both at within site and among site spatial scales. Bottom profile complexity was the most consistently important predictor studied, confirming the importance of the geomorphic template on the zonation of these species. Z. japonica's deep extent was well-predicted by Z. marina's shallow extent, but Z. marina's shallow extent was best predicted by physical factors. Using a terrestrial laser scanner, I mapped and monitored a one hectare study site for three years. The location and shape of microtopographic features were generally stable from year to year, but the magnitude of local relief was variable. Z. marina was more likely to occur in water-filled depressions than on well-drained mounds, but the presence of Z. japonica, was better predicted by low shoot densities of Z. marina. Transplant experiments revealed that Z. marina suppressed Z. japonica shoot densities, more so in pools than on mounds. Topographic context remained the most influential predictor of Z. marina responses, even when I transplanted Z. marina into higher densities of Z. japonica. I show that decameter to kilometer-scale environmental context influences the vertical zonation of Z. marina and Z. japonica, and that meter to decimeter-scale microtopographic relief influences their local spatial distribution. Furthermore, centimeter-scale topographic relief can modify competitive outcomes and promote decameter-scale coexistence of these two species.