I am currently taking BIO 182, as apparently it was the only biology course I have NOT taken at Phoenix College, and it is required for my major. It is an interesting course, made even more so by the fact that I have an excellent instructor, John Schampel.
Recently, we were able to take a field trip to the Phoenix Mountain Preserve, aka the location of Piestewa Peak, and do some field work surveying dispersal patterns of ambrosia deltoidea. This lovely little shrub is commonly known as triangle-leaf bursage, and is an important Sonoran Desert native species that is related to sunflowers. See below.
One of the benefits that this plant provides to the desert is its status as a microbiome. Bursage prefers to grow in open areas that receive a lot of sunshine, and therefore is one of the first plants to colonize hot, open spaces that are too hot for other plant seedlings. Its dense branch canopy also prevents herbivory. Bursage thus acts as a "nurse species" for other plant varieties. Over time, seeds from other species will germinate in the shade of a bursage shrub; this leads to a variety of plant species colonizing formerly open areas after bursage has taken root.
The purpose of our field trip was to survey the number of bursage plants in 81 square-foot plots, the distance from each bursage to its nearest neighbor, and the species of that nearest neighbor. To do so, we marked off the plot with flags and hand-counted/measured distances between the applicable plants. Our hypothesis was that bursage would be found to be predominantly sheltering other plants, rather than be the sole organism in its root zone, and that those plants would likely be another species.
My plot happened to be on a hillside with a lot of loose shale, so it was a little tricky to keep my footing and not pitch off into a ravine, but with the assistance of my lab partner we were able to get the survey done fairly quickly. After analyzing the results, we determined that we had 21 bursage plants in the measured plot. Of those 21 plants, 17 of them were found to be adjacent to another plant, which is an 81% rate of adjacency. Of those 17 plants, 5 were found to be another species that appeared to have germinated within the bursage canopy, which is a 24% sheltering rate. That sheltered species was exclusively creosote bush. This low sheltering rate did not support our hypothesis, yet procedural error cannot be ruled out as a factor in this result.
The dominance of bursage in the adjacency rate may be an indication of an inaccuracy in the count procedure and may have resulted in a conclusion error regarding our hypothesis. We counted each distinct crown of bursage leaves as a separate plant; however, we could not determine with 100% accuracy if each plant was a unique individual without removing the plants and conducting an analysis of the root zone(s). Thus the rate of bursage-to-bursage adjacency may be inaccurate. However, as it is already known that bursage has a distinct alleopathic root zone that prevents other plant growth when it is found to be sheltering creosote, the creosote adjacency rate appears to be accurate.
Further data is required to make an informed conclusion. Unfortunately for our lab group, only five of us showed for the field trip, so we could only make two groups and survey two plots. This makes the data we collected statistically insignificant. Nonetheless, it was fun. I enjoyed being out of the classroom for the afternoon and getting a taste of fieldwork.
That's all for now. Have a Great Week!
P.S. According to some web sources (indicated below), bursage can be used to relieve menstrual cramps and allergies. Creosote has applications, as well; it can be used as an anti-oxidant, antiseptic, and an anti-bacterial for use in minor cuts and scrapes.
Website sources to check out:
United States Bureau of Land Management
United States Department of Agriculture: Plants
Desert Eye Education
PVCC publication
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