Shadow Cliffs Regional Recreation Area is a park in between the cities of Pleasanton and Livermore, CA. It is managed by the East Bay Regional Park District. The man-made 80 acre lake was a former gravel quarry, and the area around the lake is popular for recreation. But, a bit farther away from the lake is natural habitat with hiking trails. Some of the ecosystems/landforms here include oak woodlands, riparian woodlands, tule wetland, vernally flooded areas, coyote brush scrub, and small pockets blue oak-gray pine woodland & sage scrub.
The landscape has been highly disturbed by industrial mining & invasive species, but the plants are what gives us a glimpse into the past. Starting off, geographically, the Shadow Cliffs park is at the area where the Diablo Range foothills and the Livermore Valley meet. The Arroyo Del Valle creek also flows through here. It is clear that the former gravel mining area used to be low elevation foothills, as seen from other mines nearby.
Oak woodland here is comprised of mainly Coast Live Oak (Quercus agrifolia) and Valley Oak (Quercus lobata). Some Blue Oaks (Quercus douglasii) are present aswell, concentrated on the southeast corner near Leevee Trail. Old growth Valley Oaks are also found on the south side of the park and on the adjacent Park Access Road. Miners Lettuce/Rooreh (Claytonia perfoliata) is found under oaks.
The Jolon Oak (Valley x Blue oak) is very common hybrid here. I have also found one occurance of the Gander Oak (Coast Live x Black oak).
I've also just found a uncommon and disjunct occurance of Alvord Oak/Quercus Alvordiana (Blue x John-Tucker oak) here.
Riparian woodland trees consist of Valley Oak (Quercus lobata), Fremont Cottonwood (Populus fremontii), Willows (Salix sp.), Northern California Black Walnut (Juglans hindsii), Western Sycamore (Platanus racemosa), California Buckeye (Aesculus californica), California Bay Laurel (Umbellularia californica), and Mulefat (Baccharis salicifolia).
There is a one individual Bigleaf Maple (Acer macrophyllum) by the west side creek.
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The understory includes Blackberry (Rubus Ursinus), Poison Oak (Toxicodendron diversilobum), Marsh Baccharis (Baccharis glutinosa), Wild Licorice (Glycyrrhiza lepidota), Spreading Rush (Juncus patens), Spanish Clover (Acmispon americanus), California Beeplant (Scrophularia californica), Mugwort (Artemisia douglasiana), and Rosilla (Helenium puberulum).
Wetlands consist of mainly Tule (Schoenoplectus acutus), Cattails (Typha sp.), and Willows (Salix) The surface of water is usually dominated by the aquatic Mosquito Fern (Azolla ficuloides).
On the edges of lakes/ponds you will find Tall Flatsedge (Cyperus eragrostis), Frogruit (Phyla nodiflora), Fringed Willowherb (Epilobium cilatum), Western Goldenrod (Euthamia occidentalis), Alkali Mallow (Malvella leprosa), and Alkali Heliotrope (Heliotropum curassivicum)
Honorable mentions: Coyote Brush (Baccharis pilularis) and Toyon (Heteromeles arbutifolia) are common shrubs around the park. There's a couple stands of Narrowleaf Milkweed (Asclepias fasicularis), but have not observed any monarchs near them.
In Conclusion, the Shadow Cliffs Regional Recreation Area is a small refuge for native ecosystems & wildlife, surrounded by the highly urbanized cities and active mines. I've spent a hundred hours here studying everything, and there's still lots to learn. Despite all these native plants, its still not enough. Invasive weeds have taken over a large area aswell. I am going to be restoring AND introducing some of the native biodiversity back responsibly by planting seed grown seedlings from local sources. Pleasanton & Livermore both used to have extensive wetland and creek systems, so I will be restoring riparian trees around both of those cities aswell. If anyone has any questions, comments, or concerns, please message me on Inaturalist or on instagram @momos.garden
All plant observations mentioned in this post have been associated with this journal post, see below
Shadow cliffs. Blue oaks and valley oaks both occur within the park, so obviously hybrids will form. This looks like a hybrid
Multiple young valley oaks growing on this slope, right next to a storm water runoff hole. They look so happy and growing so well with all that moisture. It’s a large cluster I assume the acorns were planted there by squirrels
Large population of Gray Pine in this area. Lots of mature trees and seedlings, and they are reproducing generously. I estimate around 70-100 individuals here.
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There are also 5-10 other scattered individuals in other parts of the Shadow Cliffs park. Looking at the geography and plants around it, I’ve come to the conclusion that this area is actually Diablo range foothills, and there used to be blue oak gray pine woodland here. The gray pine population must’ve been pushed to this corner when gravel mining started and the small hills were destroyed
Local yellow variety
Large patch of telegraph weed here, comes back every year in the disturbed area where grass is cut
Interesting leaf variation
Growing In the blue oak woodlands located in the corner of shadow cliffs regional recreation area, bordering the cemex mining area
Cluster of soap plants here, maybe 30-50 individuals total. They are also found on a slope on the adjacent park access road
Small patch of Deerweed on this slope, around 10-15 plants. Looking at the surrounding vegetation, this seems to be a remnant of the sage scrub ecosystem which probably once dominated this area. I’ll be further propagating this plant and planting in appropriate locations around this park to revive the biodiversity
Large patch of ithuriels spear and soap plant on this slope. Some blue eyed grass is present aswell
Large patches of Willowherb here
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