User: | Open Learning Faculty Member:
My initial study design includes the collection of percent covers of moss species along an environmental gradient, i.e. the slope position on a bedrock outcrop. I found that deciding on which sampling strategy to use for this exercise to be somewhat challenging. I chose a strategic sampling strategy in which samples were collected at regular intervals along a gradient. A transect was established along the environmental gradient, starting at the base of the western slope of the rock outcrop, over the crest, and down the eastern slope to the depression. Samples consisted of 18 cm by 18 cm square quadrats because this is the size that my foldable ruler, which was readily available, could produce and it seemed like a reasonable size (i.e. not too big or too small). Quadrats were located along this transect and were spaced every 40 cm.
A challenge that I had when it came to implementing this sampling method was that due to the variation in the micro-topography, there was no single transect line that would include the representative areas in each of the slope positions. I therefore had to deviate from the transect line so that the quadrats located on the western slope were all along the same transect, those along the crest and eastern slope along another, and those in the depression along yet another.
At a glance, the results of this sampling did not show a strong relationship or pattern in the percent covers of the various species. The most notable pattern was that RACCAN occurred only on the crest of the rock outcrop and PYLSPL occurred only in the depression, while DICSCO and PLESCH were present in all of the samples (with the exception of one, which lacked DICSCO). Note that 10 samples were collected instead of just 5 in order to obtain adequate representation of all of the slope positions on this particular rock outcrop while maintaining consistency in sample spacing.
I think the sampling strategy should be modified to include a broader study area, i.e. additional rock outcrops. This will broaden my scope and allow for the collection of more samples, and will also decrease the impact of any localized patterns that may not be representative of other outcrops in the area. I will try out a couple of different strategies; one option being to collect one random sample from each slope position on several different rock outcrops, and another being to simply repeat the same strategic transect methodology (but perhaps using a spacing of 20 cm instead of 40 cm in order to increase the sample number) on multiple rock outcrops. The sampling method used worked well and I will continue to use this method.
