Redwood Understory

 

Overview

            The warmer temperature of inland California draws a massive amount of fog off the Pacific Ocean.  A high surface area of the Coast Redwood’s leaves collect this moisture, providing year round access to water for the tree as well as the underlying ecosystem.  A dynamic food web has long been established and is well adapted to this shady habitat, utilizing an abundance of resources provided by these trees.

 

            The massive trees that dominate this plant community, Sequoia sempervirens, have been found on California’s coastline for millions of years. The oldest known specimens exceed 2,000 years of age; it is common to find trees living for over a millennia. The fossil record contains specimens from the genus Sequoia present during the Eocene (34 million years ago), indicating its long-standing presence on the western edge of what is now the United States. Stretching from southwest Oregon to central California, the Coast Redwood’s distribution closely follows fog patterns seen on the west coast.  California’s distinct Mediterranean climate is far too harsh for the survival of these massive trees. Without the occurrence of fog on our coastline, this plant community could not thrive and support the dynamic ecosystem beneath the forest canopy, which relies on a source of moisture in dry months. In addition, without the presence of the Redwood trees to intercept the incoming fog, moisture would bypass these ecosystems, drastically affecting the underlying community. For millions of years the Redwood forest has persisted while countless understory plant species have adapted to these damp and dark conditions. Animals and other organisms alike depend on the health of these understory plants (in return dependent on the health of the Redwood forest) for their survival and access to resources.

          Redwood Trees are able to have long lifespan because of the specie's thick, tannin-rich bark and heartwood.  Its red appearance is also from the high levels of tannic acid present in these tissues. Tannins destroy proteins, nucleic acids, and alkaloids of invading predators and pathogens protecting the attacked plant (S.sempervirens) from harm. For these reasons, the Coast Redwood is able to persist for thousands of years unharmed and able to grow hundreds of feet tall (tallest specimen pushing 500 feet).

 

-Interesting facts about Sequoia sempervirens:

i. In favorable conditions, S.sempervirens grows up to one meter per year

ii. Redwood forests have the largest biomass loadings of any ecosystem on earth

iii. After a disturbance, Redwoods commonly resprout from their stumps.

iv. During a resprouting event in deep shade, growing Redwood sprouts (blocked from light) attain resources from the mother plant allowing it to successfully regrow.

 

            Researchers estimate that only four percent of the original old growth strands of Redwoods remain. The large trees produce highly sought after wood with desirable woodworking qualities. Old growth Redwoods produce an immense quantity of this valuable wood that resulted in a logging frenzy from the days of the Spanish until the early 20th century. Today, conservation efforts work to maintain these unparalleled landscapes, ensuring the security of remaining old growths and maintaining the health of the highly dynamic ecosystem lying beneath the forest canopy.

 

A photo take looking up at the canopy of the a redwood forest, which is shrounded in fog.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig A: Sequoia sempervirens trapping the dense coastal California fog

 

 Ferns

            A Characteristic feature of Redwood forests is the abundance of ferns occupying the moist and well-shaded regions under the forest canopy. The aesthetic appeal of these plants come from the large leaves, known as fronds, that branch in radiating patterns.  In temperate regions, like California, fronds branch from the ground. In tropical regions, nearly one third of fern species are epiphytes (found growing on another plant) or have fronds that branch from a trunk that is much like a tree (hence the name tree fern).  

 

The curled up fiddlehead of a fern. Resembles a green fist and will eventually become a new fond on the fern.

 

 

 

 

 

 

 

 

 

 

 

Fig B: a fiddlehead unraveling eventually to become a fully developed frond

 

            Ferns belong to an ancient lineage of plants dating back to The Carboniferous period (over 300 million years ago). The most recent common ancestor with conifers and flowering plants occurred well over 100 million years ago. This time has allowed the fern lineage to evolve in a completely separate direction than that of the conifers (cone bearing plants) and the flowering plants seen today (see “coastal scrub” for a more detailed analysis of evolution). Ferns are often misunderstood for justifiable reasons. One, they do not produce fruit, cones, or seeds like many familiar plants. Two, ferns produce spores that divide and mature into a gametophyte. And three, this gametophyte is completely independent of the sporophyte. Before one can fully conceptualize these key differences, a sound understanding of the plant life cycle must be attained.

 

A diagram of the Alternation of generations of plants. The gametophyte produces gameters which are - and +. These gametes fuse to form a 2n zygote, which becomes a mature sporophyte. The sporophyte produces spores and each individual spore becomes a 1n gameophyte.

 

 

 

 

 

 

 

Fig C: The generalized life cycle of vascular and non-vascular plants. Gametophyte: gamete (sperm and egg) producing structure. Sporophyte: spore producing structure.

 

            From careful analysis of Figure C, one can see there are clearly two stages in a plant’s life cycle; a sporophyte stage, and a gametophyte stage. In cone bearing and flowering plants, the gametophyte stage is highly reduced and found well within the ovules of the cones and flower. In contrast, ferns have a completely separate gametophyte that exists on its own and is much larger. Essentially, the fern has two variations in its morphology depending on what stage of the lifecycle it is in. This independent gametophyte often goes unobserved, as it is generally too small (although much larger than conifers and flowering plant’s gametophyte) to identify in the field. Figure D is an example of an independent gametophyte; the product of the spores produced on the underside of fronds.

 

A close up photo of a fern gameophyte. It doesn't have fonds like the sporophyte, but instead has wide waxy leaves.

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig D: The independent gametophyte of a fern

 

Glossary

-Conifer: aka Gymnosperm; plant without seeds produced in an enclosure (ovary).

-Epiphyte: a plant that grows on another plant.

-Fiddlehead: unraveling frond of a fern.

-Flowering plant: aka Angiosperm; plant with seeds produced within an enclosure (ovary).

-Frond: large fern leaf with branching leaflets.

-Gametophyte: the gamete (sperm and egg) producing structure.

-Genus: see “Coastal Scrub” for an entire review of systematics and taxonomy.

-Mediterranean climate: long, dry summers contrasted by wet winters.

-Old growth: a forest with limited human disturbance, natural canopy openings from downed individuals, downed wood at various stages of decay, multi layered canopies, and intact soil.

-Pathogen: an organism that causes disease.

-Rhizome: a horizontal underground stem.

-Spore: single celled structure that divides into the gametophyte.

-Sporophyte: stage of life cycle that produces spores.

 

Species on Display

Vaccinium ovatum

Blechnum splicant

Dicentra formosa

Iris douglasiana

Polypodium scouleri

Gaultheria shallon

Clinopodium douglasii

Corylus cornuta

Asarum caudatum

 

References

- Peter Raven, Ray Evert, and Susan Eichhorn. Biology of Plants. Sixth. New York: W.H. Freeman and Company, 1999. Print.

-Kaesuk Yoon, Carol. "Redwood Fog Drip." Bio.net. The Oregonian, 2 12 1998

-Earle, Christopher. "Sequoia sempervirens." The Gymnosperm Database. N.p., 30 11 2012

-Boulay, M. "Redwood (Sequoia sempervirens)." Biotechnology in Agriculture and Forestry. Springer, n.d. 1989.

--Calflora: Information on California plants for education, research and conservation.

[web application]. 2008. Berkeley, California: The Calflora Database [a non-profit organization].

Available: http://www.calflora.org/ (Accessed: Oct 20, 2008).

-All photographs: Creative Commons Attribution