The ecosystems and plants of Shadow Cliffs Regional Recreation Area

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.
  ...
  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)

• Blue Oak Gray Pine woodland. Around the perimeter of the park, Blue Oaks (Quercus douglasii) and Gray Pines (Pinus sabiana) are found in scattered locations on slopes and hills, so we can infer that this woodland was widespread throughout a large portion of the park. This is a common ecosystem of the Diablo Range foothills, and similar habitat can be seen in the foothills of Sycamore Grove Park in Livermore
• Sage Scrub. There are sparse remnants of the sage scrub ecosystem scattered throughout the park. These include California Sagebrush (Artemisia californica), Black Sage (Salvia mellifera), California Buckwheat (Eriogonum californicum), Naked Buckwheat (Eriogonum nudum), Deerweed (Acmispon glaber), Yerba Santa (Eriodictyon californicum), Sticky Monkeyflower (Diplacus auranticus), Bluewitch Nightshade (Solanum umbelliferum), and Soap Plant (Chlorogalum pomeridanium).
• The presence of Yerba Santa (a large clonal cluster found on a single slope) makes me wonder if there would've been chaparral instead of simply sage scrub. Yerba Santa is a fire-dependent germinator, a feature which differentiates chaparral from sage scrub. In Del Valle Regional Park (Diablo Ranges), the chaparral and blue oak-gray pine woodland grow adjacent to eachother, sometimes even overlapping. I can only imagine it looked the same here

All plant observations mentioned in this post have been associated with this journal post, see below

Posted on September 8, 2024 10:41 PM by scion882