Analysis of the trade-off theory: Comparing growth and reproduction of American buckthorn (Rhamnus frangula) at York University

On October 17 and October 24, 2014, 3 students (Cait Carew, Lilach Halevi, and Nitharsija Srikanthan) located a woodlot on the East end of York University, Keele campus. The first day was marked by periods of overcast skies with temperatures of 11degrees Celsius and the second day with clear skies and temperatures near 15degrees Celsius during sampling hours (between 3:00-5:00pm). Observations of leaf morphology, bark, and berries identified the tree of interest as American buckthorn, Rhamnus frangula. Using a block sampling method, a transect tape was placed along the forest edge with the 0 mark aligned with the base of the first tree sample. Trees that fell along the transect tape were only observed if their diameter at breast height (dbh in cm) was greater than, or equal to 13cm. Height intervals were used to roughly estimate tree height, 1=less than 3m; 2=between 3.4-6m; and 3 greater than 6m. Height estimates were made by using known height of a student and assuming how many times bigger the tree was in comparison. Three random branches were sampled from each tree (branches defined as terminal outgrowths of approximately 40cm in length from the point of divergence from the point of attachment to the tip). The berries on each of the branches were counted, and three berries were removed, at random, from each of the three branches in order to measure the diameter using a small, millimetre measuring tape (total of nine berries per tree). The total number of berries was averaged to get the number of berries per branch and the diameter of the nine berries was used to find the average berry diameter of each individual tree. Three random leaves were also removed from each branch and the length and width were recorded. These values were used to calculate the approximate surface area of the leaf using the equation for area of a rhombus (A=[(l*w)/2]), since the leaves were elliptical and this was the easiest method of approximation. The approximate leaf area was averaged for each individual tree. The entire process was repeated for each tree which fell along the transect tape, as long as the dbh was greater than or equal to 13cm until 50 samples were obtained. Statistical analyses of berry diameter in relation to leaf area; of berry diameter in relation to tree height; and of leaf area in relation to tree height were used to identify result significance and possible correlations between tree traits.