We investigated the possible spatial structure and temporal patterns that may determine the distribution and cover of Eleocharis macrostachya and Orcuttia tenuis within two vernal pools located in Tehama County, California. Rock cover, soil depth to hardpan, and basin elevation were compared with E. macrostachya and O. tenuis cover to investigate spatial structure. Yearly E. macrostachya and O. tenuis cover were compared with yearly precipitation and air temperature to assess temporal patterns.
The spatial results suggest that soil depth to hardpan may determine E. macrostachya distribution. Rock cover and basin elevation appeared to have little effect on either E. macrostachya or O. tenuis distribution.
Temporal analyses suggest that biotic interactions such as life history traits and competition may be important factors for E. macrostachya and O. tenuis distribution and density. Orcuttia tenuis cover is relatively stable at scale of 1.0 m2 but varies at a 0.25 m2. Variability at a micro scale could be due to variations in annual air temperatures causing a possible shifting mosaic steady state. Orcuttia tenuis life history traits coincide with adaptations expected for warmer temperatures.
Even though abundance is relatively stable for O. tenuis and E. macrostachya in both pools, there is significant negative correlation and spatial structure between them. Eleocharis macrostachya may dictate O. tenuis density within a pool through a combination of abiotic and biotic features.
