A Walk Around Turtle Back, China Camp State Park
by Kathy Cuneo and Nona Dennis
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."