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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Ecosystem Services of Moist-Soil Wetlands: Water Quality Benefits and Crayfish Harvest, Economics and Consumer Acceptance

Alford, Amy Brooke 13 December 2014 (has links)
I estimated yield, population metrics, production costs, and evaluated consumer acceptability and nutritive content of crayfish (Procambarus clarkii, P. zonangulus) harvested from moist-soil wetlands in the Lower Mississippi Alluvial Valley (MAV) during springs 2009-2011. I also compared nutrient and sediment concentrations and loads exported from moist-soil wetlands and nearest agriculture fields in the MAV during winters 2010-2012. Daily yield of crayfish from moist-soil wetlands was 2.4 kg (wet) ha-1 (SE = 0.50; 95% CI = 1.3-3.4). When graded by size, yield of large crayfish (> 30 g) from wetlands dominated by P. clarkii was four times greater (P < 0.05) than yield of large crayfish from wetlands dominated by P. zonangulus. Crayfish harvesting costs (2013 US dollars [$]) ranged from $405.69 ha-1 to $917.88 ha-1 and breakeven selling prices ranged from $3.74 kg-1 to $8.49 kg-1. Consumer acceptability, proximate composition, and total fatty acid content of P. clarkii did not differ (0.73 > P > 0.11) between crayfish harvested from moist-soil wetlands and rice-crayfish culture fields in Louisiana. Although selling prices likely will not compete with prices for crayfish harvested from Louisiana rice fields ($2.75 kg-1; 2012 US$), harvesting crayfish from moist-soil wetlands may enhance recreational opportunities while increasing awareness of ecosystem benefits of these wetlands. Although concentrations (mg L-1) of soluble reactive phosphorus (SRP) in runoff from moist-soil wetlands and adjoining croplands did not differ (P = 0.95), concentrations of total and particulate phosphorus, nitrate-nitrogen, and total suspended solids were 42, 52, 86, and 89% lower (P < 0.03) in runoff from moist-soil wetlands. However, the load (kg ha-1) of SRP from moist-soil wetlands was six times (P = 0.08) greater than load from croplands. Estimated loading rate of total phosphorus from moistsoil wetlands (2.36 kg ha-1 year-1) was greater than the rate reported by regulatory agencies in Mississippi (1 kg ha-1 year-1), but field replication is needed to verify these results. Nearly 80% of the total loads exported from moist-soil wetlands occurred during < 30% runoff events. Retention of runoff from storm events may reduce phosphorus loss from moist-soil wetlands while not interfering with conservation objectives.
2

Effects of management and hydrology on vegetation, winter waterbird use, and water quality on wetlands reserve program lands, Mississippi

Fleming, Kathryn Sarah 01 May 2010 (has links)
No evaluations of plant and wildlife communities in Wetlands Reserve Program wetlands have been conducted in the Mississippi Alluvial Valley. Therefore, I evaluated active and passive moist-soil management (MTYPE) and early and late draw-down on plant communities, waterbird use, and water quality on 18 WRP lands, Mississippi, 2007-2009. Active-early sites had greater waterfowl Vegetative Forage Quality (VFQI), percentage occurrence of grass, plant diversity, and structural composition than passively managed sites (P < 0.10). I modeled variation in densities of wintering waterbirds; the best model included VFQI*MTYPE and decreased % woody vegetation (wi ≥ 0.79). Additionally, waterbird densities varied positively with active-late management (R2 ≤ 0.27), as did duck species richness with flooded area (R2 = 0.66). I compared water quality parameters among managed wetlands and drainage ditches but did not detect differences due to variability. Therefore, wetland restoration on WRP lands should focus on active management and maximizing wetland area.

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