The Time for Environmental Action is NOW!

Introduction to Natural Communities of Marin County:

A Walk Around Turtle Back, China Camp State Park

by Kathy Cuneo and Nona Dennis

Map supplied by Friends of China Camp   Turtleback is an ADA trail

Turtle Back Hill at China Camp State Park is not a large area overall, but it offers an unusually informative glimpse into three of Marin’s most common native plant communities. This walk around Turtle Back is an introduction to those communities: Tidal Salt Marsh Community and the Coast Live Oak and Native/Introduced Grassland Communities.

Begin by walking to the right on the trail, circling Turtle Back Hill in a counter-clockwise direction. 

1.  Notice that the hill to your left is made up of soil and rocks that are a light beige. These are rocks of the Franciscan Formation, probably sandstone. They are part of a prominence that was surrounded by water when ocean levels rose about 6,000 (8,000?) years ago and flooded through the Golden Gate creating the San Francisco Bay. As bay waters gradually rose, sediments washed down from the surrounding watershed were deposited in the shallows around the edges of the bay forming marshes. Because these sediments were constantly bathed by marine water, they absorbed elements of the sea salts in the same proportion as the water and thus became tidal salt marshes.   

2.  Look to the right. The extensive plant community you see is a Salt Marsh. Its apparently flat elevation is covered almost entirely with common pickle weed. The meandering “streams” are sloughs which carry freshwater runoff from the uplands during storms out to the bay, and salt water into the marsh during roughly twice-daily tidal inundation. Note that the sloughs are lined with taller plants such as salt marsh gumweed, as well as salt grass and jaumea, and at lower elevations within the edges of the sloughs are bands of California cord grass. You will also see that cord grass occurs as a broad band at the lowest marsh elevations along the bay edge. All of these plants are adapted to the clay sediment whose lower oxygen content is due to the periodic inundation by tidal water. Almost no non-native weeds grow in the Salt Marsh, as the environment is deadly to non Salt Marsh plants. Salt Marsh plants are very productive, largely perennial plants that sprout from underground roots or dormant stems each spring, flower in summer and wither in fall and winter. As the dying plant parts break up and decay into the bay water, they contribute large amounts of organic material, both as particles and eventually dissolved, which feed the large populations of filter and sediment feeders in the bay mud and water. These animals include mussels, clams, worms, shrimps, many other invertebrates and fish and these animals make possible the winter feeding stopover of the shore birds and waterfowl of the Pacific Flyway and why San Francisco Bay is the nursery for so many species.

"Deep in the waterlogged sediment and peat of salt marshes, carbon is stored at much greater rates than in land ecosystems, serving as an offset to climate change by sequestering the carbon compounds before they are oxidized to carbon dioxide (Co2) that is released to build-up in the atmosphere."

3.  To your left, and up the Turtle Back hill, you will see two plant communities forming a kind of mosaic: Native / Introduced Grassland, and Coast Live Oak Communities.  Wide areas are covered with non-native grasses that were introduced to California more than 200 years ago by the Spanish and continue to dominate many grasslands, where they out-compete native grasses. These include wild oat, soft chess, ripgut grass and Italian ryegrass, among others.  These are mingled with perennial native grasses, like purple needlegrass and wildrye, and with many native herbaceous flowering plants (wildflowers), including California poppy, owl’s clover, lupine, iris, milk maids and mule’s ears.  Grasslands, especially those with many native perennials, are typically very productive communities with roots that sequester a lot of carbon deep in the soil.  The leaves and seeds of both grasses and wildflowers support large numbers of insects and small mammals.

4.  As you proceed around Turtle Back to the north side of the hill, you will be surrounded by a woodland (Coast Live Oak Community) consisting of coast live oak, California bay, and Pacific madrone. This particular Live Oak Community is notable because it also contains three other oaks: black oak, valley oak and blue oak. The community covers much of the north side, west side and top of the hill.  Depending on amounts of open canopy, you will find a rich understory of poison oak, wild honeysuckle, snowberry, sticky monkey flower, toyon and other species. Insects feed on the leaves and wood and, in turn, are prey for birds, salamanders, lizards, and small mammals that are prey for raccoons, foxes, and bobcats. Deer are also frequent visitors, browsing on a variety of these plants. While dreaded by humans, poison oak offers valuable habitat resources for a wide variety of insects, mammals, and birds. The focal point of the community, however, is the acorn.  The acorns of the oaks are the main staple in the diets of deer, squirrels, gophers, birds such as acorn woodpeckers and quail.  In earlier times Coast Miwok people were also dependent on acorns as the basis of their diet.

Environmental Forum of Marin is a 501(c)(3) non-profit organization, and a United Way of the Bay Area Certified Agency.

© Copyright Environment Forum of Marin 2016

Powered by Wild Apricot Membership Software