Current Research 1

Saturday, October 22 at 8:00-9:40 am, Oak Room

*note alternate instance of this session – Saturday at 10am

Session Description: This students-only session provides a venue to highlight research that focuses on the California flora. A number of topics will be explored in this session, including plant taxonomy, rare plant biology, and plant ecology of both native and invasive plant species.

Session Chairs: Dena Grossenbacher (California Polytechnic State University, San Luis Obispo, San Luis Obispo, CA, USA) and Natalie Love (California Polytechnic State University, San Luis Obispo, San Luis Obispo, CA, USA)

34.1    The role of competition and soil chemistry in the community assembly of the vertic clay endemic annual plant communities of the San Joaquin Desert

Emma R. Fryer (California Polytechnic State University, San Luis Obispo, San Luis Obispo, CA, USA), Ryan O’Dell (Bureau of Land Management, Central Coast Field Office, Marina, CA, USA), and Nishanta Rajakaruna (California Polytechnic State University, San Luis Obispo, San Luis Obispo, CA, USA) 

The San Joaquin Desert (SJD) supports a high diversity of rare, endemic annual plants notable for their massive floral displays following high rainfall winters. In such years, their blooms on the extremely high clay content soils of the SJD form a patchwork of color that reflects the heterogeneous pattern of soil texture and salinity across the landscape. These vertic clay soils are physically extreme to annual plants, as the clay content of these soils causes extensive cracking upon drying, reducing soil moisture access and creating physical stress for plant roots. These soils are also often chemically extreme due to high sodium content, further rendering them inhospitable to most plants. Like species endemic to other extreme substrates (e.g., serpentine) in California, vertic clay endemic species appear to be specially adapted to these harsh soils. The non-native annual grasses have invaded the vertic clay ecosystems in some areas and begun to displace the vertic clay endemic species. The combination of a diverse suite of vertic clay endemic species (species pool), extreme physical and chemical soil abiotic factors (habitat filter), and the invasion of Bromus madritensis (competition filter) make this system ideal for studying the factors contributing to plant community assembly. This study examined twelve SJD native annuals across three vertic clay soils spanning three orders of magnitude of sodium content, and the role of competition from invasive species as a biotic factor acting on these species was addressed by a duplicate set of each species sample with added Bromus madritensis plants in each native species’ pot. Through the combination of exploratory fieldwork with these greenhouse studies, the factors shaping this community and their interaction can be understood, and the community better characterized.

34.2    We didn’t start the fire: Multi-institutional undergraduate collaboration to monitor monthly post-wildfire vegetation succession and comparison to community science datasets

Richard Rachman (California State University, Northridge, Los Angeles, CA, USA), Joey Curti (University California, Los Angeles, Los Angeles, CA, USA), Casey terHorst (California State University, Northridge, Los Angeles, CA, USA), Brad Shaffer (University California, Los Angeles, Los Angeles, CA, USA)

Wildfires are becoming more frequent and destructive in the Western United States. Human impacts on vegetation communities contribute to increased fire frequency and intensity; thus, understanding anthropogenic drivers of fire is essential to effective management. The Santa Monica Mountains, near Los Angeles, California, experience a unique combination of climatic and anthropogenic stressors that make native vegetation communities especially vulnerable to abnormal fire regimes. Among these threats are conversion of perennial shrubland habitats to ones dominated by invasive annual forbs and grasses, which often result from increased fire frequency. The Woolsey Fire in December 2018 was one of the largest wildfires in the history of the area. This wildfire burnt almost 90% of the federal land in the Santa Monica Mountains, and over 50% of the entire mountain range. We used this natural experiment to study the impacts of the Woolsey Fire and document post-fire recovery of native and invasive flora in the following six months. Undergraduate students from local universities and community colleges around Los Angeles monitored 36 sites for one to six months, starting in February 2019. Vegetation data were collected by 10 1×1 m quadrats along a 100 m transect and documented species presence, percent cover, and burn severity from burnt shrub limb thickness. Students returned month after month to collect data and photograph changes to the post-wildfire landscape. We identified species in plot photos in 2020 using student photographs and keys in the Jepson Manual (2nd edition). Statistical analysis has shown lower burn intensity associated with non-native species, particularly invasive species like annual grasses. We have also found evidence of type conversion showing increases of species richness immediately after the disturbance, mostly of fire follower forbs and invasive species. iNaturalist data was examined and found to be heavily biased towards charismatic flora, but that some species were potential indicators for high and low burn intensity. We hope this work advances both science and the careers of students often underrepresented in academia.

34.3    Long-term recovery of restored Sacramento River floodplains

Brook Constantz (University of California, Santa Cruz, Santa Cruz, CA, USA)

This research documents the vegetation characteristics of aging restored and reference forests along the Sacramento River. By the 1980s only about five percent of the Great Central Valley riparian forest remained, so the state of California setup a large restoration program to restore natural processes and habitat adjacent to the river. This research project evaluates the change over time of plant species composition and structure by following up on prior overstory and understory field surveys. My pilot data suggests that restored forests differ from reference forests in three key ways: (1) restored forest understories still have lower native species cover and (2) more exotic shrubs than reference forests, and (3) restored overstories have a similar stem density and basal area to reference forest, but a tree species composition more typical of an older floodplain.

34.4    The impacts of drought on floral traits and pollinator choice in three native southern California forbs

Annika Rose-Person (she/her) (University of California, Riverside, Riverside, CA, USA), Sydney Glassman (University of California, Riverside, Riverside, CA, USA), Louis Santiago (University of California, Riverside, Riverside, CA, USA), Nicole Rafferty (University of California, Riverside, Riverside, CA, USA)

Anthropogenic climate change is impacting plant-pollinator interactions by altering precipitation regimes. Plant-pollinator interactions are critical to the well-being of both ecosystems and humans: they maintain wild plant biodiversity and are responsible for approximately a third of global food production. However, plants and the pollinators they rely on are threatened by drought. Droughts are increasing in severity and frequency in California due to climate change, and models predict that this pattern will continue in future years. To understand how drought affects plant-pollinator interactions, we ask how water stress impacts floral traits and foraging preference of a native solitary bee, Osmia lignaria Say, using three forbs native to southern California: Phacelia campanularia (Boraginaceae), Nemophila menziesii (Boraginaceae), and Collinsia heterophylla (Plantaginaceae). In the summer of 2021, we grew individuals of P. campanularia, N. menziesii, and C. heterophylla in a greenhouse at the University of California, Riverside. Half of individuals were given ample water, and half were exposed to drought conditions. For each plant, we measured the number of flowers produced, flower size, nectar concentration, and nectar volume. We found that across species, drought plants produced flowers that were smaller (p<0.0001) and produced less nectar (p<0.001). In C. heterophylla and N. menziesii, plants exposed to drought produced nectar with higher sugar concentration (p<0.0001 and p<0.05, respectively). To explore the impact of these drought-driven shifts in floral traits on bee behavior, we will perform a choice trial experiment in May 2022. In this experiment we will record preference of female O. lignaria for drought versus ample-watered plants. This research provides novel insights into the potential multitrophic impacts of drought stress on plants and their interactions with pollinators, and explores mechanisms behind bee foraging behavior.