Around 8:30 this morning, I went out with my friend Roxanne for a walk at the Jepson Prairie Preserve with one of my Certified California Naturalist graduates and botany expert, Charlie, and a handful of other folks (including several of my former students). Altogether there was Charlie and his wife Lynn, Roxanne, Karlyn, Kelli, Deborah, Karen, Bill, and David.
And, OMG, I learned so much from Charlie, I can hardly begin to remember it all. First, though, let’s talk a little bit about the preserve itself. It’s overall about 2.5 square miles and comprised of relatively prairie land, mima mounds, and a variety of vernal pools. It’s one of the few surviving vernal pool habitats and native bunchgrass prairies in the state.
The whole thing is surrounded by agricultural land. The largest, deepest pool is called Olcott Pool, a large “playa pool” that can be seen, when it’s full, on both sides of the road. In 2021, there was so little rain that the water covered an area about the size of a bath tub. This year, it was much more impressive. Part of the pool was turgid, dirty-looking, and Charlie explained that was because the clay in the bottom of the pool is super fine and stays in suspension all the time.
Part of the property is divided by rail road tracks, another part is divided by a road, and there are huge powerline towers that crackle with electricity. They’re owned by PG&E.
The preserve is primed for wildflowers each years by allowing sheep to graze the land in a managed fashion.
“…Two years after the Nature Conservancy purchased the 1,566-acre site, it was dedicated as the Willis Linn Jepson Prairie Preserve in 1982. In 1983, the University of California brought the preserve into the University’s Natural Reserve System. In 1987 the National Park Service designated Dixon Vernal Pools, of which Jepson is the centerpiece, a National Natural Landmark…” So, it’s a very special place.
Here is part of the writeup on the place from the preserve’s website and brochure:
“…Vernal pools are temporary bodies of fresh water created by winter rains. A clay layer just under the surface soil expands and creates an impermeable barrier, so rainwater fills the low spots as the soil is saturated. These pools become the habitat for a complex world of plants and animals which adapted over time to survive a habitat that floods in winter and then dries completely during the hot summer months…
“…The reserve protects several seasonal playa lakes and one of the best remaining networks of clay-pan vernal-pool habitat in the Central Valley… Altogether over 400 species and 64 families of plants, including 15 rare and endangered plants, are found on site…
“Many of the showiest vernal pool flowers (Yellow Carpet, Meadowfoam, Goldfields, and Downingia) are pollinated by native specialist bees in the family Andrenidae. These solitary, ground-nesting bees use the pollen of specific flowers to feed their young. And, during the course of collecting pollen to provision their nests, they perform the vital function of cross-pollinating the vernal pool flowers…Each of the four plant groups listed above has one or more native specialist bees that collects pollen only from them. The life cycle of these bees is closely synchronized with that of their pollen host flowers. While generalist and non-native bees, such as the honey bee, and other insects also visit most of these flowers and may potentially pollinate them, research shows that at least some of these flowers may require their specialist pollinators for successful reproduction and seed set…”
You can read more in an article from Bay Nature magazine HERE.
This was the first time I’d been there, and even though I couldn’t walk as much of the landscape as I would have liked – [no stamina] – I was impressed.
The first thing Charlie, who is a docent there, did for us was to go into the larger pool before we arrived and fished out some samples of the tiny creatures and larvae that swam in the water. He wasn’t able to find any Tiger Salamander larvae or the rare Conservancy Fairy Shrimp, but he did find lots of copepods, some California Clam Shrimp, and some Vernal Pool Tadpole Shrimp [which look like tiny Horseshoe Crabs to me]. Such fascinating stuff.
Here’s more information on them from the preserve’s website and brochure:
“…Vernal pool tadpole shrimp complete their entire lifecycle within the seasonal pools flooded by winter and spring rains. Adults can reproduce several times within one wet season, and some adults can produce fertilized eggs on their own. Adult Vernal pool tadpole shrimp die when the pools dry out, but eggs are surrounded by a shell that protects the embryo from drying out. These cysts remain in a dormant phase — also called diapause — for years if necessary. With suitable temperatures and rainfall, some cysts in the vernal pool soils will hatch, sometimes in as few as four days. The rate at which the young reach sexual maturity depends on water temperature, but sexual maturity usually occurs between 21 and 28 days… Cysts can pass unharmed through the digestive system of other organisms and may be deposited in new locations through this process… With no guarantee that a pool will stay wet long enough for hatching cysts to complete their lifecycle, having only a portion of cysts hatch in any given season makes it possible for the species to survive years of insufficient rainfall…”
Charlie told us the anecdotal story of a rock filled with the cysts sitting on the shelf in the office of a biology lab for about 70 years, and when the rock was submerged in water, the shrimp hatched out. He said there was also an experiment of putting one of the cysts over a Bunsen burner and then putting it into water… and the shrimp emerged unharmed. Amazing little critters!
Among the samples Charlie had fished from the pool were some of the crabs with eggs. I was hoping to get a photo of that, but those individuals were uncooperative and kept their backs to my camera. The shrimp are hermaphrodites and according to Encyclopedia.com, “…[Individuals] surviving to large size may lay up to six clutches of eggs, totaling about 861 eggs in [its] lifetime. The eggs are sticky and readily adhere to plant matter and sediment particles. A portion of the eggs hatch immediately and the rest enter diapause and remain in the soil to hatch during later rainy seasons…”
“…They eat (and swim) by beating their leaf-like feet in a wavelike motion from front to back. They catch food with their feet. Their feet then move food up a groove that runs up the middle of their underside, toward their mouth. They are very aggressive omnivores. They eat algae, bacteria, protozoa, rotifers, aquatic earthworms, insects, Fairy Shrimp, frog eggs and tadpoles…”
When we were done looking at the creatures, Charlie returned them back to the pool so they could go on with their day and their lives.
CLICK HERE for the full album of photos.
Then we went wildflower hunting. We saw quite a few different species, most of them adapted to growing in the vernal pool environment, some of them quite short and stunted, or very, very small. My favorites were the Maroonspot Calicoflower [a kind of downingia], the Dwarf Brodiaea, and the Sea Mullia [which I’d never seen before].
I couldn’t keep up with the entire group after a while and had to return to the car, but the group went on to fine two other species of downingia. So exciting!
Charlie was telling us about how the invasive vetches [which are members of the pea family] can severely alter the alkali prairie by their presence. They fix nitrogen in the soil thereby changing the profile of the ground to a less alkaline state – one not in tune with the preserve’s natural environment. It’s a very specialized, unique and somewhat tenuous habitat that needs to be protected or we’ll lose all of the rare, endemic, and endangered species currently found there.
After our walk, Rox and I went into Dixon for lunch, and stopped at Bud’s Pub and Grill for sandwiches before heading back to Sacramento.
- American Avocet, Recurvirostra americana
- Backswimmer, Notonecta sp.
- Bee, European Honeybee, Western Honeybee, Apis mellifera
- Blow Wives, Achyrachaena mollis
- Blue Dicks, Dipterostemon capitatus capitatus
- Brass Buttons, Cotula coronopifolia
- Bufflehead Duck, Bucephala albeola
- Canada Goose, Branta canadensis
- Chilean Trefoil, Acmispon wrangelianus
- Clover, Bearded Clover, Trifolium barbigerum
- Copepods, Family: Cyclopidae
- Crow, American Crow, Corvus brachyrhynchos
- Downingia, Maroonspot Calicoflower, Downingia concolor [vernal pool]
- Dwarf Brodiaea, Brodiaea terrestris terrestris
- Fiddleneck, Common Fiddleneck, Amsinckia menziesii
- Field Owl Clover, Castilleja campestris campestris
- Fremont’s Goldfields, Lasthenia fremontii
- Goldfields, Smooth Goldfields, Lasthenia glaberrima [tall]
- Gopher, Botta’s Pocket Gopher, Thomomys bottae [burrows, mounds]
- Grasses, Purple Needlegrass, Nassella pulchra
- Grasses, Ripgut Brome, Bromus diandrus
- Grasses, Saltgrass, Distichlis spicata
- Grasses, Silver Hairgrass, Aira caryophyllea
- Great Blue Heron, Ardea herodias
- Groundsel, Common Groundsel, Senecio vulgaris
- Johnny Tuck, Butter-and-Eggs, Castilleja eriantha eriantha
- Ladybeetle, Convergent Lady Beetle, Hippodamia convergens
- Lomatium, Biscuitroot, Lomatium sp.
- Lupine, Miniature Lupine, Lupinus bicolor
- Meadowfoam, Rosy Douglas Meadowfoam, Limnanthes douglasii rosea [vernal pool]
- Pineappleweed, Chamomilla suaveolens
- Popcorn Flower, Greene’s Popcorn Flower, Plagiobothrys greenei
- Purple Sanicle, Sanicula bipinnatifida
- Red-Winged Blackbird, Agelaius phoeniceus
- Sea Mullia, Muilla maritima [white flowers, sort of like onion]
- Shining Pepperweed, Lepidium nitidum
- Shrimp, California Clam Shrimp, Cyzicus californicus
- Shrimp, Vernal Pool Tadpole Shrimp, Lepidurus packardi
- Smooth Cat’s Ear, Hypochaeris glabra
- Stork’s Bill, Mediterranean Stork’s-Bill, Erodium botrys
- Tree Swallow, Tachycineta bicolor
- Vetch, Hairy Vetch, Winter Vetch, Vicia villosa villosa
- Violet, California Golden Violet, Viola pedunculata
- Water Boatman, Subfamily: Corixinae
- Western Meadowlark, Sturnella neglecta
- White-Faced Ibis, Plegadis chihi
- Woolly Marbles, Low Woolly Marbles, Psilocarphus brevissimus
- Yarrow, Common Yarrow, Achillea millefolium
- Yellow Carpet, Glue-Seed, Blennosperma nabium var.nanum [tiny yellow flower with white pollen]
- ?? dragonfly larvae, Suborder: Anisoptera
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