In the previous portion of my field research project, I focused on observing five replicates in Location 2 of my selected sites. The trees along the road were numbered, and I randomly selected five individual trees using an online number generator. This sampling method was effective given the layout of the trees, which allowed for easy identification as discrete units. However, I anticipate difficulties in applying this method to my other two locations due to a higher number of trees, so I will likely need to adopt a different sampling strategy for those areas.
The sample unit was each selected tree, and I took measurements on the four cardinal faces of each trunk to ensure consistency, especially since determining sunlight exposure on each face can be challenging. Initially, I planned to record a categorical response variable (lichen presence/absence), but I found that nearly all the trees exhibited some degree of lichen growth. This prompted me to adjust my approach to measure lichen cover as a percentage instead.
To accomplish this, I used a chicken wire grid with 10 horizontal and 10 vertical holes, positioned at chest height on each tree trunk. For instance, if half of the hexagonal spaces contained lichen, I estimated a 50% lichen cover. However, the grid was too large for some trunks, extending beyond their edges, and the hexagonal shapes complicated the establishment of clear measurement boundaries. To address this issue, I will use a smaller-sized measuring grid for the remainder of the project.
The results I gathered were both unexpected and unsurprising, as I feel I still lack sufficient information to draw any definitive conclusions about the relationship between lichen growth and sunlight exposure at this stage.
Sounds like a good start! Things are always confusing in field studies, focus on your sampling strategy and what will work and don’t worry too much about the results, they will be what they are!