Competitor species were introduced into randomly selected treatment and control containers
after 54 days. On day 85, a subset of previously sprayed treatment containers was randomly
selected for a second spray application. After 239 days, all vegetation was removed from
treatment containers and separated into root and shoot sections. Fresh cumulative stem heights
were obtained to the nearest millimeter during processing. Above ground, below ground, and
total dry biomass was to the nearest mg obtained after plant material was placed in drying ovens
at 400C for five days.
Statistical Analysis
After harvesting, a two-way analysis of variance (ANOVA)(SAS Institute 2003) was
used to test effects of competitor species, herbicide application frequency, and all interactions on
total A. philoxeroides dry biomass, above ground dry biomass, below ground dry biomass, fresh
cumulative stem length, and dry shoot/root ratio. A duplicate analysis was run with individual
species combined as monocots or dicots. Data met requirements for normality and
homoscedasticity. Means were considered significant at p < 0.05. When significant main effects
or interaction effects were detected, multiple comparisons were conducted using the Bonferonni
correction (Zar 2009).
Field Experiment
The field component of this project occurred within an oxbow of the Trinity River
adjacent to the city landfill in Grand Prairie, Texas (96056'35.793"W 32046'27.035"N) (Figure
5). The oxbow covers an approximate area of 7.5 hectares and is subject to periodic flooding
after heavy rains. A. philoxeroides was first reported within the oxbow area in 2008 and was
widespread by 2010. A. philoxeroides growth in the oxbow may best be described as rooted
emergent. As a follow up to the greenhouse component of this project, the field component used
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