Ellen Bauder

Diapause allows aquatic organisms to survive periods of drydown in intermittent pools. However, often not all of the individuals hatch in response to a filling event. This prolonged diapause can be a bet-hedging adaptation to unpredictability in the duration of filling events. Under the simplest bet-hedging model of selection on prolonged diapause, the fraction of eggs hatching in any filling event should approximate the fraction of filling events lasting long enough for successful reproduction. We quantified filling durations in seven vernal pools in San Diego County inhabited by the endemic fairy shrimp Branchinecta sandiegonensis (Branchiopoda: Anostraca) for all winter and spring events from 1983 to 1996. For any given rainfall event, larger, deeper pools held water longer than smaller, shallower pools. However, the distributions of filling durations did not differ significantly among these pools, so selection should be similar across pools. Approximately 28 percent of the filli...

Because resources are finite, conservation practices can be based on shortcuts (i.e., a quicker way to a desired outcome). For example, indicator species are often used as a shortcut to justify conservation at greater organizational levels (i.e., communities, ecosystems, landscapes). Conversely, "coarse-filter" approaches to protect landscapes are often assumed to conserve organizational levels nested within that landscape. But is conservation biology fundamentally different from other applied sciences, in which shortcuts appear rare or absent? To evaluate this question requires a rarity; much data across organizational levels in numerous well-defined systems. We used data collected in vernal pools (N = 61) in greater San Diego, California and seasonal wetlands (N = 70) in Florida. Data for plant species of concern, plant community diversity, ecosystem function, and landscape integrity were evaluated using partial least-squares structural equation models. Three a priori al...

Vernal pools are small, temporary ponds that fill are filled by winter rains and dry up by late spring. Often the ponds are well defined, sometimes functioning more or less independently, but usually they are interconnected by shallow drainages, especially in rainy years. In some cases the entire habitat consists of drainages and swales with the pool or pond component less noticeable. Occasionally the ponds are large enough to be considered vernal lakes, the center of which may actually hold water year around or at least long enough for a fresh water marsh to develop. Pools form in flat or gently sloping landscapes over an impervious soil layer, usually clay, which can be underlain by basalt, granitic rocks or a hardpan formed of clays or cobbles cemented together. In San Diego County, the majority of the pools, have in addition to clay surface soils, a hardpan layer beneath them made up of cobbles held together by a combination of iron and silica.

This Draft Guidebook is an assessment tool that focuses on the functioning of vernal pool wetlands within the Southern Californian eco-region, specifically San Diego County. Its purpose is to provide trained practitioners the means to achieve efficient, reproducible and logical functional assessment results for vernal pool wetlands in San Diego County, California. Results of these assessments can then be used in a variety of ways, such as evaluation of sites for restoration potential, assessment of impacts from existing or proposed projects and monitoring restoration success. Due to the high degree of variability experienced by temporary wetlands in arid climates, we have developed both direct and indirect functional indices for four of the five functions we identified. Direct assessments can only be made when there is sufficient precipitation to elicit the responses that demonstrate function, and we have sought to objectively define "sufficient." Consistent with an HGM ap...

California vernal pools were used to develop and test hypotheses related to species response patterns and distributions along environmental moisture and elevation gradients. Data from three rainfall years were examined for patterns of plant distribution in relation to length and frequency of inundation and relative elevation. Field distributions on elevation and inundation duration gradients were characteristic of each species, with species distributions overlapping along the gradient. Plants with limited inundation tolerance (`Non-Pool' species) responded to wet years by shifting their distributions toward the dry end of the moisture gradient and in the dry year toward the wetter end. These species have most of their distribution outside of pools. Species with limited tolerance to the gradient extremes had their peak frequency in intermediate positions (`Edge' species). `Pool' species had substantial inundation tolerance. Several were near the limits of inundation tolerance in the deepest study pools, but others withstood longer inundation. `Pool' species had static distributions on the elevation gradient, growing in whatever conditions prevailed in a particular year. A number of annual `Pool' species had their highest frequency in the intermediate, moderately wet year. The dry year had a strong negative effect on the frequency of a few `Pool' annuals, but established perennials persisted regardless. In general, results of the regression analyses can be understood given the other information available on pool hydrology and vegetation. They do not produce any obvious hypotheses to test. For a given species, variables have different predictive value, depending on the year.