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Sample Date and Time: 2/7/21 10:40AM
For my initial sampling, I chose to use the systematic sampling method utilizing five 0.25 m2 quadrats spaced approximately two meters apart along a transect that ran in the heading of 110 degrees for approximately eleven meters. This transect was placed along my initially observed gradient of elevation from sea level. My initial sampling location was along the western rocky outcrop of the headland island. Within each quadrat, percent cover was recorded and indicated with one of five classes of percent cover ranges.
The most obvious difficulty for sampling the abundance of the stonecrop is and will be the accessibility to the sample points. As the stonecrop appears most abundant on the steeper rocky faces, some sample points may not be accessed safely and easily. When placing additional transects within each study area, this will have to be accounted for while trying to minimize sampling bias. Repeat transects within each study area will help minimize any bias from adjusting the transect locations.
My initial data collection generally agreed with my initial hypothesis that stonecrop abundance is negatively affected by increased substrate moisture as a higher abundance was measured at areas with well-draining, rocky substrate. However, it was noted that substrate alone may not be the best indicator as two samples that had rocky substrate had very little to no abundance of the stonecrop. It was also noted that the substrate type was generally consistent throughout the entire transect indicating that either a better predictor variable is needed or the transects should be longer (i.e run farther inland). The absence/presence of moss on the rocky substrate or degree of slope seem to be better predictors based on this initial sampling.
Going forward with full sampling I will continue to use transects and quadrats as these seem to be the most effective and efficient methods to capturing stonecrop abundance. Transect lengths will be increased which will necessitate additional quadrats. Each of the three study areas will have five transects with evenly spaced quadrats along each transect. An additional alteration will be to the percent cover classes used as my lowest class used (0-20%) may be too large a range to capture very small abundances.
