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I took a couple month hiatus from field work to allow for the snow to melt and for the temperatures to get above freezing, in order to discover organisms I may not have otherwise encountered in winter. I set out on May 6 at 20:00 to the same park I had previously established as my field study site. On my walk I discovered a speckling of trees with bracket fungi (or polypores) growing near their bases. A rough guess would suggest that the prevalence of trees with polypores is about 1 in every 100 trees, including both deciduous and coniferous species. I am curious about what conditions foster the growth of these fungi and if any correlations can be made.
- Identify the organism or biological attribute that you plan to study.
Polypore fungi on deciduous and coniferous trees
- Use your field journal to document observations of your organism or biological attribute along an environmental gradient. Choose at least three locations along the gradient and observe and record any changes in the distribution, abundance, or character of your object of study.
I encountered five occurrences of trees with polypores. All but one tree had polypores growing on the east side of their trunk. One tree had fungi growing on the northwest side. All but one were 50cm or less to the base of the trunk. One tree had growths that extended up to breast height. Each tree occurred near other trees (either deciduous or coniferous) that did not contain any fungi. However, the fungi-infected trees seemed to occur in isolation, in the sense that each one was spaced fairly far apart, at least 20 metres or more. None were clustered together from my initial site inspection. Three of the trees were poplar and two were black spruce. All had diameters at breast height (DBH) of at least 20cm.
- Think about underlying processes that may cause any patterns that you have observed. Postulate one hypothesis and make one formal prediction based on that hypothesis. Your hypothesis may include the environmental gradient; however, if you come up with a hypothesis that you want to pursue within one part of the gradient or one site, that is acceptable as well.
Process
From initial field inspection, it appeared that the bracket fungi predominantly produced flowering bodies on the east side of the tree trunk on larger trees that were enclosed within a fair amount of canopy cover. This makes me wonder if factors such as sunlight, wind, moisture, tree height and other physical factors affect where the flowering bodies appear.
Hypothesis
The distribution of bracket fungi is determined by tree location within the environmental gradient.
Predictions
- Bracket fungi are more likely to develop in well shaded densely populated areas.
- Bracket fungi grow on older and taller trees, on both deciduous and coniferous species
- Bracket fungi flower on the side of the tree that has reduced exposure to wind.
- Based on your hypothesis and prediction, list one potential response variable and one potential explanatory variable and whether they would be categorical or continuous. Use the experimental design tutorial to help you with this.
Potential response variable: occurrence of bracket fungi (Categorical)
Potential explanatory variable: degree of canopy cover (continuous)
This study would be logistic regression because the response variable (presence/absence of bracket fungi) is categorical while the explanatory or predictor variable (degree of canopy cover) is continuous.
When I replied to your email I forgot you had put canopy cover in your blog post. You could keep this as your variable with the sample design suggestions that I gave you via email. You would systematically choose plots that include trees with fungi and those without.