Sedgwick Reserve

19 Jun, 07 PM - 23 Jun, 10 AM

Over the last 7 years, I have observed an extensive, seemingly stable population of Camissonia graciliflora (Hook. & Arn.) Raven on a serpentine-Paso Robles formation contact on the slopes of the San Raphael Mountains, California. The site is located in the upper Lisque Canyon of the UCSB Sedgwick Reserve. Beginning in 2001 I have observed some annual variation in populations size exhibited at this location. The dominant form found in the populations is cleistogamous (CL) individuals. These plants exhibited minute, sealed corollas perched on rapidly developing capsules in the very early growing season (late December-January). By mid-season (March-early April), the fruit matures with the capsule appressed downward against the soil surface. The stem dries in this position and remains so over the summer drought period. Once fall rains arrive, the capsule stands erect immediately after the onset of precipitation and the capsule dehisces. The open valves form a splash cup structure and the seeds are likely dispersed by raindrops. Selfing plants are most common on the stable serpentine derived soils between tussocks of native perennial bunchgrasses (Nassella pulchra) whereas outcrossing or chasmogamous (CH) individuals are very uncommon and isolated at the edge of slightly weathered Thomomys bioturbation mounds. I hypothesize that the cleistogamous (CL) populations develop in stable soils with chasmogamous plants developing in the looser soils of the rodent burrows in response to increased soil moisture and organic matter. Considering the size of the selfing populations, I predict that establishment of individuals from seed of the autogamous parents will be greater on un-bioturbated microsites than on those sites with evidence of bioturbation. In these later sites, the chasmogamous seed would more successful establish seedlings. In the two years of the study, I will conduct both field and greenhouse experiments to test the hypothesis. Following, initial observations and seed collection in 2007, I propose conducting detailed surveys in the field in winter-spring 2008 and 2009 to characterize the seedling establishment of the CL and CH derived seed in relation to presence or absence of bioturbation. In the greenhouse study, I will compare seedling establishment in a variety of soil types and compactions. I would propose very local and minor (hand dug using trowel) artificial manipulations to simulate rodent bioturbation in the reserve study site. Outside of this hand troweling, limited seed collection, marking with wire, plastic flagging and painted nails set at ground level, I do not anticipate any other disturbance to the field sites.

Visit #12969 @Sedgwick Reserve

Approved

Under Project # 8515 | Research

The ecological role of facultative cleistogamy in a serpentine annual plant

faculty - Butte College

Reservation Members(s)

Michael Williams Jun 19 - 23, 2007 (5 days)

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