Epiphytes Provide High-Up Base for Biodiversity

Epiphyte Communities on Sitka Spruce in an Old-Growth Redwood Forest

Sitka Epiphytes.
Sitka Epiphytes.

William Ellyson and Stephen Sillett found evidence that demonstrates that epiphytes—plants that use other plants for mechanical support—play a crucial role in maintaining the biodiversity of redwood forest canopies. It’s well known that these hangers-on thrive in the old-growth Douglas-fir forests of Oregon and Washington, in places amassing the weight of two concert grand pianos per acre. Ellyson and Sillett reveal in this study that Douglas-fir has a rival in Sitka spruce, a tree that grows in and among northern coast redwood forests and supports a shockingly high diversity of epiphytes.

The researchers suspended themselves from ropes high up in the forest canopy to identify and count epiphytes on Sitka spruce trees in the old-growth redwood forest of Prairie Creek Redwoods State Park. At the end of a survey of five spruce trees, they had tallied 91 species and weighed an average of 60kg (161 lbs) of live epiphytes and 131kg (289 lbs) of dead organic matter per tree. Though they found lichens, bryophytes (i.e. mosses), and ferns co-mingling on branches, bryophytes dominated overwhelmingly.

This is especially important because the sponge-like bryophyte mats capture nutrients from rainfall. In addition, with their capacity for holding water, they make available an abundance of moisture for associated organisms. Fungi, beetles, crickets, earthworms, millipedes, and mollusks inhabit thick bryophyte mats during the rainy season. Higher order organisms including the endangered marbled murrelet, wandering salamanders, and rodents make use of them too.

It’s clear from this research that epiphytes are not only on the take. While exploiting tree branches for support, these easily overlooked plants boost biodiversity in redwood forests.

-William Ellyson’s report was published in the journal Bryologists under the title “Epiphyte Communities on Sitka Spruce in an Old-Growth Redwood Forest”

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