Take Me To the River

photo credit: Western Sycamore Achene Balls by Eugene Zelenko on creative commons

Winter's flood stage on the Nacimiento River has calmed down to a clear running flow. Trees that were stranded bare and submerged in running water several months ago are now solidly perched on the streambanks and beginning to green with spring growth. It's incredible that anything could survive such forceful surges but many of the species we encounter down at the river depend upon seasonal flooding.

Willows (Salix sp.) are well-adapted to inundation. Their extensive root systems help anchor them against strong currents. If they remain underwater for more than a few days they produce specialized roots directly from their trunks and branches. These roots absorb oxygen from the air and deliver it to submerged tissue. Their tenacity creates the foundation for stabilized river banks and the resulting habitat for a diverse number of species. As if this were not enough, willows are insect-pollinated and attract flying insects. These in turn provide food for birds, bats, and amphibians.

Alongside the willows, western sycamores (Platanus racemosa) and white alders (Alnus rhombifolia) share the canopy and help to anchor the moist banks. White alder, named for its pale foliage, is a deciduous tree with smooth, silvery-gray bark covered with lace-like colonies of white lichen.

The sycamores are identifiable by their peeling bark in patches of tan, gray, and white. The fruits mature in a burr-like ball that hangs from the branch. The ball is not a single fruit but rather, a globe made up of many tiny hairy fruits. They are light and float on water, which aids in their dispersal. The sycamores are important host plants for the Western Tiger Swallowtail butterflies emerging now in numbers since the weather has warmed.

Below the trees, clumps of sedge (Carex) form tufts of flat leaves and delicate catkins on triangular stems. Their extensive system of rhizomes helps bind soils and prevent streambank erosion. Like their tree neighbors, the sedges provide food and cover for a variety of animals. 

My favorite resident of the riverbank is the chick lupine (Lupinus microcarpus var. densiflorus). Although pink and purple lupines abound in our area, the densiflorus variety of chick lupine is the only white lupine in California.

 

In the Pacific Coast Ecoregion, 60 percent of amphibian species, 16 percent of reptiles, 34 percent of birds, and 12 percent of mammals are considered obligate riparian species (Kelsey and West 1998). Once again I am reminded how fortunate I am to live here and how important it is to champion this sacred trust.