User: | Open Learning Faculty Member:
The organism I am studying is the Arbutus species native to southern British Columbia and the Pacific Northwest in the USA: Arbutus Menziesii. The biological attribute I am examining is the health and colour of the foliage of the tree, as Arbutus trees in this area seem to be in varying health dependent on location (the environmental gradient).
I sampled 21 trees from 15 locations, and further divided these locations into 5 closely clustered regions as a way to measure how different environments effect the species and environmental gradient. The first grouping (1) contains 3 locations and 4 trees in a thick forested region. Group 2 contains 4 locations and 5 trees in a less dense forested region. Group 3 contains 3 locations and 3 trees in an even thinner forested region with some areas that appear open and free of large trees. Group 4 contains 2 locations and 2 trees in an area that is filled with sparse forest and more regions of cliffs and a lack of tall trees. The 5th group contains 3 locations and 9 trees. This area has the most open spaces, sparse vegetation and open cliffs.
In general Arbutus trees seemed to be smallest and with a larger proportion of unhealthy leaves in forested areas, and particular in areas where the surrounding area consisted of tall trees above the arbutus species.
The largest arbutus trees with the most healthy leaves were all in the least forested areas and particularly those growing on the cliffs.
The black leaves may be caused by a fungus or other microorganism, but I believe that trees that face environmental factors that hinder their ability to grow and stay healthy will be more susceptible to disease. In particular I believe that Arbutus trees have a very hard time growing and staying healthy in areas where they are overcrowded by the canopy of taller trees and competition for resources in the soil, hence why I have observed trees in poor health all in heavily forested areas with tall tree canopies, and very little ill health on cliffs and in sparsely patches of forest with smaller trees. Other factors such as access to water can be discounted as Arbutus trees are very hardy and can withstand long periods of drought. Additionally the unhealthy leaves persisted throughout the summer and the winter, which are periods where Denman Island experiences a dry season and then a wet season.
This topic is very interesting. You seem to have a good grasp of what it is you need to do in order to complete this study, and if it were up to me, I wouldn’t constructively criticize you at all. The only things that jump out at me are the different number of locations and number of trees within those locations. It would seem to me that statistically, those areas, such as group 4 with 2 trees, may not provide you with enough information to statistically compare to other groups properly, such as group 5 which has 9 trees. But I also understand that time and space are limited, so I think you have done your due diligence in conducting a study with the resources available. Again, I think it is a good hypothesis and best of luck!