Exploring the Relationship amongst Interacting Plant Communities of Solidago canadensis and Symphyotrichum ericoides as Distance from a Water Source Increases

In order to better understand the relationship between plant height and distance from a water source, a study was conducted on successive weeks during the afternoons (from 2:30PM to 5:00PM EST) of October 1st, 8th and 15th 2015 at York University’s Keele campus (43° 46' 9.228"N, 79° 30' 29.556’’W). We selected three sources of water (Stong Pond, Black Creek Pond and Dan Iannuzzi Park Pond) with similar characteristics in terms of surrounding herbaceous vegetation (all three locations were dominated by herbaceous perennial plants), canopy coverage (little to no canopy coverage), and elevation gradients and soil types. The two plants in question were the Symphyotrichum ericoides (white aster) and the Solidago canadensis (Canadian goldenrod), both of which are native to North America. A stratified random sampling procedure was adopted where the area surrounding each water source was stratified into three concentric categories based on soil type: dry, weathered and wet (Figure 2). Soil types at approximately 3 m were considered “wet,” at 12 m “weathered” and at 15 m “dry.” These three strata were visually identified based on a consensus of all four observers in the study, in order to minimize estimate errors due to observer bias. At all three locations, one line transect was transversed at the most shallow edge of the pond. A one by one meter quadrat was then placed from the point where the transect ends. The direction of quadrat placement for each stratum was determined through a randomization procedure, using a random number table on Microsoft Excel. In each sample plot, the following variables were measured: plant height and distance from water source. Plant height was measured using a second transect, where we measured from the base of the stem to the apical bud. Plants measured along quadrat margins were included if more than half of the rooted system was visibly inside the quadrat. Three replicate plots were sampled for each stratum, at each location, resulting in a total of 81 replicates. Mean temperature and precipitation during the month of October in southern Ontario ranged from 14-18 °C and 64 mm, respectively. We conducted statistical tests using SPSS where the independent variable was distance from water source and the dependent variable was plant height. We performed a one-way ANOVA to compare differences in plant height as distance from the water source increased, based on soil type. Means were separated by application of the Tukey post-hoc test. We considered there to be no significance when the value of the probability of significance (p-value) was greater than 0.05. To further test whether there were differences in growth between the two species, regardless if one was inherently smaller than the other, we used a two-tailed, independent sample t-test assuming equal variance.

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