Ecology Lab 5: The Effects of Density and Sunlight Exposure to a Maple Trees Growth

<strong>Hypothesis:</strong> Testing the effects of density and sunlight availability on a trees growth or its diameter at breast height (DBH). <strong>Methods</strong>: Observations and data were collected at the York University Keele campus in the woodlot. A target species was selected to be Maple trees. The target tree to be observed was selected randomly by walking 10 steps north and 5 steps east. A 10 meter radius was laid around the target tree, the number of plants within the radius were counted and recorded in order to determine the density. This includes adult trees and saplings, which were defined to be any tree at least 3 meters in height. The diameter at breast height was measured and recorded as well as the percentage of sunlight coverage. This was done by standing directly against the tree facing towards the direction of sunlight, using a 4′ by 6″ quadrant to estimate the amount of sunlight the tree is exposed to. A new tree was selected at least 5 meters away from the outside of previous radius to avoid recounting. A random maple tree was selected once again by walking 10 steps north and 5 steps east and selecting the closest maple tree outside the previous radius. The process was repeated for a total sample size of 35 maple trees. <strong>Predictions</strong>: Assuming that the density and sunlight availability are independent of each other the following predictions can be made. - High density creates competition amongst species for resources (water, space, nutrients), negatively effecting the tree growth (small dbh) - High density can mean there is an abundance of resources available in that location which positively effects the trees growth (large dbh) - Large canopy coverage means there is competition for sunlight, negatively effects growth (small dbh) - Small canopy coverage, low competition, high exposure to sunlight which positively effects growth (large dbh)