User: | Open Learning Faculty Member:
The organism I would like to study is Douglas Maple (Acer glabrum). More specifically, variation in its abundance along a spatial gradient from a mature Western Cedar (Thuja plicata).
For initial observations compass bearings of 20°, 40°, and 60° were taken from the base of the T. plicata. Along each of these bearings, plot centers were established at 5, 10, and 15 m. Each plot was 1m2 and the number of A. glabum within each was recorded, as shown in the table below.
| Distance from T. Plicata in m | # of A. glabrum along 20° bearing | # of A. glabrum along 40° bearing | # of A. glabrum along 60° bearing |
| 5 | 0 | 0 | 0 |
| 10 | 3 | 8 | 4 |
| 15 | 5 | 2 | 6 |
During the time observations were taken, the entire plot site that was <5m from T. Plicata was in the shade and the 5-10m part of the site was in full sun.
The entire site is located on west facing hill that is has a 12% slope.
I did the above observations before watching the study design videos and I now know that what I did is a systematic sampling method. Upon further reflection, and after watching all the vids, I’m thinking it makes more sense to do a random sample method as explained by Lyn Baldwin. So, I did a second sample methodology using an app to generate random compass bearings and paces to locate 1×1 m plots in 10 different locations within the site. The following was observed using this method:
| Paces from base of T. Plicata | Compass bearing (°) | Number of A. Glabrum in plot |
| 2 | 35 | 0 |
| 5 | 34 | 0 |
| 3 | 22 | 0 |
| 6 | 92 | 0 |
| 15 | 19 | 5 |
| 11 | 88 | 2 |
| 3 | 42 | 0 |
| 5 | 84 | 0 |
| 0 | 57 | 0 |
| 6 | 79 | 0 |
Some processes that may be causing the variation in species abundance is the shade from the large conifer, differences in soil moisture content, differences in mineral composition, or distance from the conifer. However, my main hypothesis is that the shade created by the T. plicata reduces the stand density of A. glabrum by reducing the availability of incoming solar radiation. To help test this hypothesis, observations will be made as to how much sunlight and shade the site is in throughout the day.
The response variable is A. glabrum and all of the processes listed above are predictor variables. The response variable is continuous as it is being quantified by counting and the predictor variables are all continuous. Therefore, I infer that this is a regression experimental design and inductive methods will be utilized to test my hypothesis since initial observations of reduction in stand density as distance from the conifer increases will try to be explained.
