Vernal Pool Management at Olcott Lake, Jepson Prairie Preserve-Solano Land Trust Project
The 1566-acre Jepson Prairie Preserve, owned by the Solano Land Trust, is one of California’s best remaining examples of claypan vernal pool and native bunchgrass prairie, habitats once widespread in the Central Valley but now mostly converted to agricultural or other development. The pools host a unique assemblage of plants and animals through a brief life cycle which must be completed before the pools and grasslands dry in the unremitting summer heat.
Vernal pools exceeding an acre in size are generally termed playa lakes and the largest of these within the Jepson Prairie Preserve is the 93-acre Olcott Lake. This vast lake usually reaches full capacity by January and is one of the last to dry as summer approaches.
Compared to the surrounding landscape, Olcott Lake supports a disproportionately high number of threatened and endangered species (Table 1). These species are well adapted top the extreme conditions in the lake and most spend the dry season in varying states of dormancy.
Table 1. Threatened and endangered species at Olcott Lake
Common Name |
Scientific Name |
Status |
Plants |
|
|
Gratiola heterosepala |
SE |
|
Neostapfia colusana |
FT/SE |
|
Tuctoria mucronata |
FE/SE |
|
Navarrettia leucocephala spp. bakeri |
R |
|
Downingia pusilla |
R |
|
Animals |
|
|
Branchinecta conservatio |
FE |
|
Lepidurus packardi |
FE |
|
Elaphrus viridis |
FT |
|
Ambystoma californiense |
R |
FE=Federally Endangered SE=State Endangered
FT=Federally Threatened R=Rare
* Not seen in over 5 years.
Because Olcott Lake presents such difficult living conditions, the threat of non-native invasive species is much less than the uplands region within the preserve. However, physical disturbance continues to pose a threat via unrestricted sheep access and off road vehicles. The Land Trust closely controls grazing on the preserve so that livestock damage is minimal. However, the threat of off road vehicles is high because of the close proximity of the Argyle Park motorcycle and go-kart track. Off road vehicle traffic from Argyle Park occasionally ventures down Cook Lane, the County road that bisects the preserve. In the summer time, the desiccated clay surface of the Olcott Lake presents a tempting area in which to ride. To date, there has been little trouble with vehicles entering the dry lake but the fence is currently in a state of major disrepair both along the frontage roads and within the one of the pastures. The easy access to the lake will undoubtedly be viewed as an invitation to some. Additionally, as the fences continue to deteriorate, it will become increasingly difficult to control sheep movement.
The Land Trust proposed to replace the fencing along approximately 3,800 feet of frontage road and 1,400 feet bordering the Eucalyptus pasture. By doing so, it is able to more effectively manage livestock and make certain that off road vehicles do not stray into this extremely sensitive and rare habitat. Four hiker accessible gates will be installed to allow movement of sheep for grazing and vehicle entry for prescribed burning. Signs will be posted informing visitors of the fragile nature of the habitat.
The project was completed in April of 2004.
