I went back to the Desierto de Los Leones National Park in Mexico City to continue my sampling. I’m focusing on a flower commonly known as the mountain rose (Eryngium monocephalum) as my subject of study. The park is located in mountainous terrain, and during my first visit there, I found the plant only at the top of the mountains. My current hypothesis is that E. monocephalum requires large amounts of incident light to grow, and any tree coverage or other shadow sources will hinder their growth. My prediction is that the abundance of mountain roses increases with elevation.
To verify my prediction, I plan to measure the number of E. monocephalum per area at different elevations. To minimize background variation, I decided to conduct my sampling on the side of one mountain, “Cerro El Caballete .” That way, incident light, temperature, and other important variables are assumed to be constant across all samples. In addition, I chose this mountain because of its accessibility from below and above – there is a trail on the top and another in the middle.
I decided to do systematic sampling along five different elevations and take 10 samples on each (50 total). My predictor variable is elevation which I will measure alongside each sample using the altimeter on my Garmin (fenix 6 pro). For my predictor variable, I will be measuring the density of mountain roses using a 2×2 m sample unit. Using Google Earth, I traced approximately where I would sample (Image 1) on the mountain.
I went on my third field site visit on May 8th. I arrived at 9:33 am and left at 1:20 pm after doing a 12 km in and out hike to the top of El Caballete hill. It was a very hot day with an average temperature of 29 C, with a max of 35 C and a low of 24 C.
I went to take the first 5 measurements and see the viability of my proposed sampling strategy. I decided to start at the top, next to the trail. I took five samples every 15 meters by placing my quadrant and alternating between the left and right of my “elevation line.” Since I was on the trail, I didn’t have much difficulty taking the samples; however, when I tried to go a bit off-trail, it was hard to walk due to the tall grasses and rocky terrain, which might make it difficult to take samples at the lower elevations.
From the data I collected, I was surprised to see that the flower appears to grow in clumps because it had large numbers where I could find it, but otherwise, it was pretty sparse. For example, I had 16 specimens in one sample (Image 2) and 0 for the rest. I will continue using this approach, but if I find it difficult to measure beyond the trail, I will have to think of another sampling technique.
