Today’s post is all about the work I’ve been doing at a University of California Natural Reserve in eastern Riverside County, Oasis de los Osos. For nearly 2 years, I’ve been visiting Oasis de los Osos regularly to monitor plants and arthropods.
Oasis de los Osos is a small reserve (65 hectares) adjacent to the Snow Creek community of Palm Springs, CA. A perennial stream “Lamb’s Creek” runs through the reserve and supports dense riparian vegetation, amphibians, and many other critters seeking reprieve from the desert heat. The remains of a former home sit alongside the stream near the southwestern edge of the reserve; it was allegedly built in the 1930s by Denver and Lucy Ellen Lamb (see this site for more details).
My monitoring study is set up to assess the plant and arthropod biodiversity that occurs close to and distant from the perennial stream, and changes that occur along its drying portion. In particular, I aim to figure out how plants and arthropods respond to the presence and dominance of the invasive weed, Brassica tournefortii.
Twelve transects are established at every 100 meters along the stream, from the perennially flowing region at slightly higher elevation, to the seasonally wet/dry region below. Within each of these transects, five plots are set up at 0, 4, 8, 16, and 32 meters away from the stream edge. This design allows me to compare the identity and diversity of plants and arthropods that occur at varying positions along the stream, and at varying distances away from it.
At each plot, I have set up one pitfall trap and one platform for a set of pan traps. Pitfall and pan traps are used to passively sample arthropods that occur in the area. Pitfall traps capture critters walking along the ground, and are often used when targeting detritivores, predators, and shy critters. Pan traps capture flying arthropods that come in to land on what they likely thought was a flower; pan traps are generally used when targeting pollinators and other flower-visitors. Because they sample different kinds of arthropod critters, I use both kinds of traps at each plot to assess what kinds of animals live there.
Pitfall and pan traps are left open for 24 hours each census period. At this time, the plants growing at each plot are also censused to document variation in which species are present.
Several people help me with each census – 60 plots is a lot! We each set up traps at a few transects on the first day, carefully opening pitfall traps, attaching pan traps, and filling them with soapy water. Hiking with water jugs is made much easier with several helping hands.
On day 2, we each work at a few transects to collect all of the specimens captured in the pitfall and pan traps at every plot. The soapy water and contents are emptied from the trap cups into special baggies to be transported back to the lab, all the cups are collected, and the pitfall traps are closed and covered up to prevent any critters getting in there between censuses.
We’ve found some pretty interesting critters in these traps! There have been 30 different orders of arthropods identified (An order is a taxonomic grouping level above family but below class. For example, ants and bees are in the order Hymenoptera, while butterflies and moths are in the order Lepidoptera).
Back at the lab, all the samples are transferred to glass vials with ethanol and given labels to keep track of where and when they came from.
Once all specimens are transferred into glass storage vials with ethanol, they are ready to be examined under a microscope, identified and counted. This data will be used to understand the arthropod community at Oasis de los Osos, how it changes in response to the plant community, time of year, and other environmental variables.
Stay tuned for updates as more data is generated and analyzed!
Unless otherwise noted, all photos used here are my own. Please feel free to comment or contact me with questions!