For my ongoing field observations, I visited Pipers Lagoon on Sunday, January 17th at 9:43 am. The weather was overcast, 6 degrees in temperature, and no wind.
1. Identify the organism or biological attribute that you plan to study.
The organism I plan to study is the Broad-Leaved Stonecrop, sedum Spathurifolium.
Figure 1: Broad-Leaved Stonecrop
2. 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.
During my first field observation, I had noted that the Broad-Leaved Stonecrop was generally only found along the ocean-facing rocky outcrops and not present on the lagoon facing ones. The plant is able to grow within various cracks and crevasses in the rocky outcrops. During this field observation, I decided to use the elevation from sea level as my gradient as well as exposure to the sun and the ocean. I also decided to focus on just the headland island portion of the park.
I chose three different locations along the headland island, all with similar topography (open, exposed cliffs, primarily moss/lichen/stonecrop dominant). These were the northeast rocky outcrop, northwest rocky outcrop, and the south/southwest portion of the headland island.
Figure 2: Observation Locations
Along the rocky outcrop of the northeast side of the headland island, the stonecrop generally grew from mid to high elevation from sea level, with no growth at all below the high watermark. It was typically most abundant mid to high elevation, with less abundance along the plateau. As the amount of sun exposure throughout the day differed (i.e morning vs afternoon) it was noted that the abundance and distribution of the stonecrop increased (i.e more abundant and more area covered along the west side of the rocky outcrop than the east). Again, the growth was most pronounced at mid to high elevation and tapered off along the plateau. It was also noted that the stonecrop more exposed to the sun throughout the day had a more reddish color to its leaves than those that were in less sun-exposed areas.
The northwest rocky outcrop of the headland island had a similar growth regime (i.e mid to high elevation, tapering off at the plateau). It was noted that the stonecrop distribution spread beyond strictly the rocky outcrop on this portion of the headland island. A large abundance was observed along a steep slope farther inland than the rocky outcrop.
The Southwest portion of the headland island had virtually no presence of stonecrop, despite being a similarly rocky, sun-exposed area. However, there was certainly more soil and much less hard rock here than the more sea cliff type rocky outcrops in the other areas. This area also has no exposure to the open ocean while elevation gain from sea level was much more gradual and smaller than the much sharper increase in northeast and northwest portions of the headland island.
3. Think about underlying processes that may cause any patterns that you have observed.
Some underlying processes that may cause the patterns observed include the moisture and drainage of the substrate that the stonecrop grows in, the type of substrate, and the amount of sunlight exposure.
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.
Based on my observations of where the stonecrop was found to be thriving I hypothesize that stonecrop abundance is negatively impacted by increased substrate moisture. Therefore I predict that the stonecrop will be most abundant in areas with at least half-day sun exposure and bare, exposed rock.
4. 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.
One potential response variable would be the abundance of stonecrop while one potential explanatory variable is substrate type. Substrate type would give an indication of the amount of moisture the stonecrop is exposed to as well as the drainability of water in the area. The response variable would be considered continuous (i.e abundance in terms of percent cover) while the predictor variable would be considered categorical (i.e type of substrate). This would classify the experimental design as being ANOVA.
Field Notes: