Selected Highlights of the April 16, 2022 Field Trip to Jepson Prairie
Field Trip Leaders: Charlie Russell and Russ Huddleston, Solano Land Trust
Field trip Report: by Susan Schlosser
In late Fall vernal pool plants start to grow in the inundated areas of the Jepson Prairie pools. By early March a succession of wildflowers start blooming in large masses along the edges of evaporating vernal pools providing a colorful and beautiful site. A succession of flowers will bloom as the pools dry down, through the end of May. In the vernal pools, aquatic invertebrates hatch from eggs and cysts to complete their life cycle in a few months. California Tiger Salamanders crawl from their burrows on dry land back to the pools to reproduce. We enjoyed this beautiful and delightful ecosystem on a cool and cloudy day with our field trip leaders, Charlie Russell and Russ Huddleston.
Figure 1. Group photo on shore of Olcott Lake
The Solano Land Trust owns Jepson Prairie Preserve and manages it with the University of California Natural Reserve System. The primary goal is to maintain the native species and their habitats. Vernal pools used to be a very common habitat in the Sacramento/ San Joaquin River Delta and in the Central Valley. They are now rare and few are protected.
We started out sitting on picnic benches facing Olcott Lake, the largest pool at Jepson Prairie. Much research on the vernal pool ecosystem has been completed over the last few decades. We heard a fascinating introduction to vernal pools, the soils that created them, the adaptations of plant and animals that live here, and their seasonal ecosystem.
An impenetrable layer of clay, about 1 foot below the surface now, washed down from the nearby Inner Coastal Ranges over the preceding millennia. Rain fills the pools in winter and they dry out by evaporation through summer. The visible water of the vernal pools is an exposed water table. There is also a large “playa” vernal pool here that receives some runoff from the watershed. Jepson Prairie is relatively flat with some small hummocks called ‘mima mounds’ that are not inundated and whose origin is still being studied.
A succession of plants and animals grow and reproduce in the vernal pool habitat. Plants tend to be annuals that grow, flower and produce seeds that are dropped and dry in place. Animals such as shrimp and salamanders have complex life cycles that utilize the wet, winter phase to grow and reproduce. Many invertebrates produce cysts that survive over summer in the in bottom of the pool and hatch out when the rains start. California Tiger Salamanders, crawl to burrows on land within 100 days of hatching. When winter rains start when mature adults return to the pools to start their cycle again.
Figure 2. Tadpole shrimp (live, in aquaria)
At Olcott Lake. Russ Huddleston gave an outstanding presentation with live animals he had netted that morning. Isopods, aquatic insects, fairy shrimp, tadpole shrimp and juvenile California Tiger Salamanders were shown individually, in small clear plastic aquaria that were passed around for each participant to see while Russ described their life history. It was extremely fascinating and interesting to see the fauna living right there in Olcott Lake. Many of these animals live here as their predators, fish, cannot survive in such seasonal waters.
Figure 3. Juvenile California Tiger Salamander (live, in aquaria)
As we stood learning about the aquatic life at Olcott Lake, at our feet were many of the flowers we came to see. Right there, just inside the gate of the public trail, were Lasthenia fremontii, one of the seven Lasthenia species found here and keyed before the field trip by Charlie. 
Figure 4. D. insignisThese species require a microscope to dissect the flower and then determine the species. Other wildflowers within feet of where we stood, included two species of Downingia: Dwarf Downingia, D. pusilla and Cupped Downingia, D. insignis, field owl’s clover (Castilleja campestris ssp. campestris), Baker’s navarretia (Navarretia leucocephala ssp. bakeri), semaphore grass (Pleuropogon californicus var. californicus), pale spikerush (Eleocharis macrostachya), and on the nearby mima mounds: alkalai-meadow mallow (Malvella leprosa,plant only), Purple needle grass (Stipa pulchra), gold nuggets (Calachortus luteus, Charlie commented they were blooming 2 weeks earlier than he had ever seen in 10 years of leading tours), dwarf brodiaea (Brodiaea terrestris) and many non-native grasses.
Across the road we traversed large areas of L. fremontii and maroon-spotted downingia, D. concolor var. concolor. Other plants we saw in this alkaline playa pool area included: Coyote-thistle (Eryngium vaseyi), blow-wives (Achyrachaena mollis), brass-buttons (Cotula coronopifolia), smooth goldfields, which is a rayless species (L. glaberrima), woolly-marbles (Psilocarphus brevissimus), popcorn flowers (Plabiobothrys spp., seeds are the definitive characteristic and not visible yet), 
Figure 5. D. concolor var. concolor and Navarretia leucocephala ssp. bakeriminiature lupine (Lupinus bicolor), winter vetch (Vicia villosa ssp. villosa), alkali heath (Frankenia salina), hyssop loosestrife (Lythrum hyssopifolia), purslane speedwell (Veronica peregrina ssp. xalapensis, plants in seed), salt grass (Distichlis spictata), northern barley (Hordeum brachyantherum ssp. brachyantherum), Sacramento beardstyle (Pogogyne zizyphoroides), white brodiaea (Tritelia hyacinthina), lowland cudweed (Gnaphalium palustre), and the irresistibly named turkey tangle frog fruit (Phyla nodiflora ,plant only).
Jepson Prairie Preserve has many uncommon, rare and endangered plants. This article only touches on a few of them. There is a public trail at Olcott Lake where anyone can view many of these plants from easily visible footpaths. It is well worth a visit to see the plants, enjoy the expansive beautiful landscapes and views of surrounding mountains, and watch herons, egrets, hawks, and many other birds in the pools and surrounding area.
All photos by Susan Schlosser.
Figure 6a. Landscape at Playa Pool
Figure 6b. Identifying plants