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Visited Whispering Woods September 20, 2019
Time: 16:34 – 15:30
Location: Whispering Woods Park, NW Calgary
Weather: 13°C, mostly cloudy
The purpose of this fieldwork was to observe aspen trees, Populus tremuloides, located in Whispering Woods. One of the environmental gradients present at this location is a 12m change in elevation from the bottom to the top of the Woods. Therefore, I chose to observe health attributes of P. tremuloides trees located at the bottom, middle, and top of this hill. The specific attributes I observed were leaf colour (percent of primarily yellow leaves on the trees), soil moisture (measured using a HoldAll® Moisture, Light, and pH Meter™), and soil pH (also measured using a HoldAll® Moisture, Light, and pH Meter™). Soil moisture and pH measures were taken 20-30cm from the base of the tree. Additionally, I looked at general differences in the distribution, abundance, and character of these trees located at the bottom, middle, and top of the hill.
As indicated from the field journal documentation, there were character differences present including the percentage of yellow leaves, soil moisture, and soil pH of the 30 trees sampled (10 from each level of gradient). The bottom of the hill contained trees with almost completely green leaves, a higher average moisture, and a medium average pH. The top of the hill contained trees with primarily green leaves on its West side, and primarily yellow leaves on its East side. Further, trees on the top had the lowest average soil moisture, and most alkaline average soil pH. Trees located in the middle of the hill had a combination of characteristics from both.
Additionally, I observed differences in the abundance of trees, as the top NW contained the densest area of trees, while the bottom SE corner contained the least. These dense trees were also smaller in size on average. The distribution of yellow coloured leaves also was a clear finding, with primarily yellow-leaved trees located on the East side, and primarily green-leaved trees located on the West side for both the trees sampled from the middle and top of the hill. Another important note is that there were not enough trees to sample from the bottom SE corner relative to the width of the hill, so samples taken from the bottom of the hill were taken from trees all on the SW side.
From these observations, I have compiled a hypothesis and a prediction. It is important to note that in this stage of my Field Project, I am choosing to define the “health” of these trees as green leaves, high soil moisture, and a neutral soil pH. As the Fall season progresses, I hope to include other relevant indicators, such as rate of leaf loss, and perhaps water infiltration rate.
My hypothesis is that there is a significant difference in P. tremuloides health (based on the definition above) among trees located along the elevation gradient of Whispering Woods hill. My null hypothesis would therefore be that there is no difference in P. tremuloides health among trees located along the elevation gradient of Whispering Woods hill; any difference is due to chance alone.
Based on this hypothesis, I can make certain predictions regarding the attributes of health I have chosen. I predict that trees located at the bottom of the hill will have a better overall health, indicated by a higher average green leaf percentage, higher soil moisture, and a neutral soil pH. Conversely, I predict that trees located at the top of the hill, on average, will have a worse overall health, indicated by a lower green leaf percentage, lower soil moisture, and a more alkaline soil pH. These predictions are based on my previous knowledge of what plants require to grow optimally.
From these predictions, the response variable would be indicators of tree health (soil moisture, percent green leaves, soil pH) which is a continuous variable. The explanatory variable would be the position of the tree on the hill (bottom or top) which is a categorical variable.
