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April 28, 2017 – Friday 12:00-13:30
Weather: 5.5 degrees C. 35 Km/hr wind. No recent precipitation. Snow still present on the North and East slopes. Ice cover on Eskers Lakes, but Pond 1 is ice-free. 5 diving ducks on Pond 1 and ducks are present on the open shoreline of the lakes where snow and ice is melting.
The organism that I plan to study is Labrador Tea (Ledum groenlandicum). Walking along the bottom of the slope of Pond 1, the North slope has a lot of Labrador Tea, particularly under the canopy of spruce trees. There is not a lot of pooling water on the North side as there is a constructed drainage ditch that reports to the wetlands proximal to Eskers Lake West. Photo 1 illustrates the sparse occurrence of Labrador Tea in open areas with no canopy. Photo 2 illustrates the difference in density and abundance when there is spruce tree canopy cover.
Walking along the 300 m stretch of wetland below the east-facing slope of Pond 1, there is a very obvious pattern of Labrador Tea growing in dense patches directly below the smaller spruce trees. There is no drainage ditch along the East slope but there is also no pooling water. Further towards Eskers Lakes, the distribution and abundance of Labrador Tea greatly decreases as the ground becomes more flooded. Within the forested area Labrador Tea is beginning to grown green leaves.
Along the South-facing slope there are larger Englemen Spruce trees. The abundance of Labrador Tea is low under the larger trees. There appears to be a preference for the smaller Black Spruce. Again, the spatial distribution of Labrador Tea is greatest in moderately well-drained soil directly under the canopy of smaller spruce trees.
Underlying processes explaining why Labrador Tea is greater in density and abundance directly below smaller spruce trees:
- soil moisture – Labrador Tea does not appear to thrive in flooded or saturated soil conditions
- Slopes – Labrador Tea does not appear to grow on steeper slopes, though aspect does not appear to be a factor
Hypothesis (Inductive): The abundance and density of Labrador Tea is determined by substrate moisture.
Prediction: Areas proximal to wetlands will have greater abundance and density of Labrador Tea than either the flooded areas of the wetlands or the well-drained slopes.
Null Hypothesis: Soil moisture has no effect on the abundance and density of Labrador Tea.
Response Variable: Labrador Tea
Predictor Variable: Soil moisture.
The response variable, Labrador Tea, is categorical (may measure as presence/absence) and the predictor variable, soil moisture, is continuous. This appears to be a a Logistic Regression study design.
Hi there,
I’ve been following your research blog post and would like to comment on it. It seems to me that you have a well thought through hypothesis that is clear and falsifiable. However, I find that the response and predictor variables could be defined a bit better. The response variable that you chose in my opinion is the appropriate to be used, but it seems that if it’s measured as a continuous variable the results will show a more complex relationship between plant presence and soil moisture (rather than presence/absence). Before I read your study, I have never thought of a technique used to measure soil moisture which made me question how these data could be obtained for your study. I found that this data can be represented by two variables Soil Moisture Tension and Soil Moisture Content. These predictor variables will allow you to find how the abundance of Labrador Tea is dependent on the amount water present in the soil and on how hard it is to extract that water which is more specific than just Soil moisture.
I hope you find my comments helpful. Good luck with your research, looking forward to read your results!
Best regards,
Artem