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dc.creatorMerendino, Michael Todd
dc.date.available2011-02-19T01:08:43Z
dc.date.issued1989-12
dc.identifier.urihttp://hdl.handle.net/2346/22672en_US
dc.description.abstractInformation on critical drawdown dates for establishing emergent vegetation, as well as flood tolerances of seedlings recruited from the seedbank during one-season drawdowns, is lacking. Vegetation establishment was determined from seedbank samples for four drawdown dates (15 May, 15 June, 15 July, and 15 August 1988). On each of the four treatment dates, 24 samples were drawn down from a submersed (50cm flood) treatment and kept at drawdown level. The highest shoot densities (shoots/m^) and highest percentage of flowering shoots for alkali bulrush (Scirpus maritimus) and hardstem bulrush (Scirpus lacustris) were recorded in the 15 May drawdown. Shoot densities of cattail (Typha spp.) and purple loosestrife (Lythrum salicaria) were highest in the 15 June drawdown. The 15 July and 15 August drawdowns resulted in reduced shoot densities for all species, except red goosefoot (Chenopodium rubrum), which had maximum densities in the 15 July drawdown. Plants recruited in the 15 July and 15 August drawdowns failed to flower that year. Drawdowns in either May or June will establish first season emergent cover, but purple loosestrife and cattail may invade June drawdowns, causing management problems. Late drawdowns (July and August) inhibit establishment of first season emergent cover. Maximum seed production occurred with the 15 May drawdown. Therefore, drawdowns should be conducted as early as possible to promote seed production by perennial emergent plants. On 15 May 1989, samples from each of the four drawdown treatments the previous year were flooded to one of four reflood depths (+15cm dry, -15cm flood, -30cm flood, and -50cm flood). Samples remained flooded until 15 August 1989. The earlier water was removed the previous year (1988), the more water could be applied to the area the following year (1989). Total shoots, total flowering shoots, and biomass was lowest in all drawdown date treatments, in the -50cm flood. Alkali bulrush, hardstem bulrush, and whitetop were the dominant emergent species in all reflood treatments. Alkali bulrush performed best (highest shoot densities, and biomass) in the 15 May drawdown, for all reflood depths. Shoot densities and aboveground biomass of hardstem bulrush were highest in the 15 May drawdown, at a -30cm reflood depth. In the -15cm treatment, hardstem bulrush production was lowest in the 15 August drawdown samples, whereas, in the +15cm treatment, no differences were detected among the drawdowns. Whitetop performed best in the 15 July drawdown, in the +15cm and -15cm treatments. Whitetop establishment was minimal in the -30cm treatment. the 15 May drawdown. Therefore, drawdowns should be conducted as early as possible to promote seed production by perennial emergent plants. On 15 May 1989, samples from each of the four drawdown treatments the previous year were flooded to one of four reflood depths (+15cm dry, -15cm flood, -30cm flood, and -50cm flood). Samples remained flooded until 15 August 1989. The earlier water was removed the previous year (1988), the more water could be applied to the area the following year (1989). Total shoots, total flowering shoots, and biomass was lowest in all drawdown date treatments, in the -50cm flood. Alkali bulrush, hardstem bulrush, and whitetop were the dominant emergent species in all reflood treatments. Alkali bulrush performed best (highest shoot densities, and biomass) in the 15 May drawdown, for all reflood depths. Shoot densities and aboveground biomass of hardstem bulrush were highest in the 15 May drawdown, at a -30cm reflood depth. In the -15cm treatment, hardstem bulrush production was lowest in the 15 August drawdown samples, whereas, in the +15cm treatment, no differences were detected among the drawdowns. Whitetop performed best in the 15 July drawdown, in the +15cm and -15cm treatments. Whitetop establishment was minimal in the -30cm treatment. During the 1989 treatments, cattail and purple loosestrife failed to re-establish in densities that had been recorded the previous year (1988) . Belowground biomass of these two species was absent in all reflood treatment levels, indicating that these species did not survive the winter, or died upon reflooding.
dc.format.mimetypeapplication/pdf
dc.language.isoeng
dc.publisherTexas Tech Universityen_US
dc.subjectReservoir drawdown -- Manitoba -- Delta Marshen_US
dc.subjectWetland ecology -- Manitoba -- Delta Marshen_US
dc.titleThe response of vegetation to seasonality of drawdown and reflood depth
dc.typeThesis
thesis.degree.nameM.S.
thesis.degree.levelMasters
thesis.degree.grantorTexas Tech University
thesis.degree.departmentWildlife Science
dc.rights.availabilityUnrestricted.


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