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Plant communities in vernal pools are distributed along continuous elevation gradients associated with subtle variations in microtopography, reflected in spatially heterogeneous hydrologic regimes. We quantified the role of hydrologic and environmental variables for influencing species assemblages within two vernal pool landscapes in northeastern California. A novel combination of approaches including remote photography of water depth stage gauges, vegetation sampling along elevation gradients, and topographic surveys were used to measure hydrology and plant community composition at precise locations. Multivariate analyses were used to classify vernal pool plant communities and classification tree analysis was used to model plant community distribution across hydrologic thresholds. Three plant community groups were distinguished according to localized hydrologic regimes. Inundation period and maximum depth were the only variables found to be predictive of plant distribution. Hydrologic thresholds for the three community groups were based on inundation period: Short (< 71 days), Medium (≥ 71 days but <209 days), and Long (≥ 209 days). The distribution of plant assemblages was strongly correlated with key hydrologic gradients. Quantification of such relationships will be useful in forecasting ecohydrological responses of vernal pool vegetation to climate change, helping to guide future monitoring, management and restoration efforts for these unique ecosystems. [ABSTRACT FROM AUTHOR]

Fire-prone serotinous California Hesperocyparis L. (cypress) have been experiencing low seedling recruitment, underscoring our need to better understand these species' responses to fire. We investigated the specific heating conditions required to break cone serotiny and to promote seed dispersal by focusing on five Hesperocyparis species of interior California: Hesperocyparis nevadensis (Abrams) Bartel, Paiute cypress; H. bakeri (Jeps.) Bartel, Baker cypress (also known as Modoc cypress); H. forbesii Jeps. Bartel, tecate cypress; H. macnabiana (A. Murray bis) Bartel, McNab's cypress; and H. sargentii (Jeps.) Bartel (Sargent's cypress). A muffle furnace was used to conduct eight temperature treatments of 250 °C to 700 °C, ranging in duration from 30 seconds to 5 minutes of exposure. The heat-released seeds were tested for viability using a tetrazolium red stain. Logistic regression analysis of seed viability indicated that duration of heating alone was highly significant (P < 0.005) for all species, regardless of temperature, with durations of 1 min or less resulting in the greatest viability. Hesperocyparis forbesii and H. nevadensis were capable of tolerating temperatures as high as 700 °C. Models predicting seed viability reflected interspecific differences, with H. macnabiana and H. sargentii having higher seed viability than H. nevadensis and H. forbesii, which had higher seed viability than H. bakeri. Lab results coupled with field observations following fire suggest that fire can trigger a massive release of seeds, overwhelming the inherently low viability and allowing for greater potential for adequate seedling establishment. [ABSTRACT FROM AUTHOR]