Synthesis
The data is in and honestly, it’s pretty surprising:
I expected to see a huge jump in diversity in both the scrub and forest communities as we went to communities that were more isolated. While there was definitely a steady increase in diversity with the forest community, the scrub community threw me off. Turns out, Millard Canyon offered the most biodiversity of the 3 scrub communities I studied. Switzer falls was really lacking in scrub diversity.
My hypothesis is that the level of human disturbance has a great effect on the diversity of a community.
The key word here is HUMAN disturbance. When looking back at the three sites I studied and how much humans passed through them, I can’t say I’m too surprised at my findings.
The forest communities had a reasonable level of increase in diversity. The more room these large oaks and pines had to grow, the more shade they were able to offer and the more moisture in the air and soil was being retained. This created desirable conditions for shrubby plants to grow in their understory, which served as habitat and resources for wildlife. These oaks, when left undisturbed created great and self-dependent ecosystems. In both Lower Arroyo and Millard Canyon, there were demarcated trails that passed through both forest communities. These trails are big and heavily trafficked, whereas the oak community in Switzer Falls didn’t have that level of foot traffic.
I’ve already mentioned that the scrub community was different - it was a lot harder to map out. The conditions of Millard Canyon were dry, hot and really exposed - yet it was the most diverse scrub community I saw. The community I mapped was on the side of the trails, but had a lot of room to grow upwards. The plants seemed to really benefit from the direct sunlight. The larger bushes like laurel sumac were planted higher up and created enough shade for plants like black sage and California sagebrush. While trails cut through these communities, they were not as heavily trafficked, because they were not immediately in areas where people walked through them. And the trails they were on were really empty.
In Lower Arroyo, there was just not enough nutrients. There was a wide open space for the scrub community to grow, but all the plants were really spread out from each other and the area was heavily trafficked by humans and horses. In Switzer Falls, the scrub community I studied was in the parking lot. There was a heavy staircase that went through this community and it was at a pretty steep slope. People came up and down the staircase a lot, and lots of cars drove past this community daily.