Earthworms have colonized most of Portland’s forested natural areas and have transformed many aspects of the soil, plant interactions, and nutrient cycling. Earthworms eliminate the soil duff layer by consumption of plant material and bioturbation. They transform the spongy topsoil layer into a compacted one with nutrient-rich worm castings on the surface. This creates conditions ideal for disturbance resistant plant species and can impact habitat for amphibians, invertebrates, and ground-nesting birds. Earthworms increase the leaching of nitrogen and phosphorus, reduce mycorrhizal abundance, increase water infiltration, increase soil bulk density, and reduce the diversity of native plants. Using the mustard extraction method, we surveyed forested natural areas throughout Portland for earthworms. We found introduced earthworms to be abundant on most plots with some sites have densities of over 2 million per acre. The effects of these “ecosystem engineers” have been overlooked and need serious consideration in the management of natural systems. With no realistic way of eliminating earthworms, managers need to determine new strategies for achieving restoration goals in colonized sites.
Acknowledging the effects of earthworms will change our perception of how natural systems function. Is what we assumed as plant-plant competition a shift in the underlying ground rules, manipulated by earthworms?
We will learn about a few common earthworms and how to identify them. And we will look at their impacts, how they travel, and where they have been found in Portland. And we will examine what new approaches we can take, now that we understand their transformative force.
When: March 15, 2018 , 5:30-8:00 (room opens at 5:00)
Where: Rogue East Side, 928 SE 9th Ave.
Who: Toby Query
What: Portland's Got Worms! How earthworms are transforming the ecosystem