Effects of Knotweed Restoration on Riparian Vegetation
Japanese, giant, and bohemian knotweeds are invasive plants that
spread aggressively and reduce plant species diversity by establishing
dense knotweed monocultures. Restoration efforts require many years
of intensive surveys and chemical applications to the knotweed. The
restoration objective and assumed outcome is a return to a native plant
assemblage. To examine this assumption, we are measuring the diversity
and composition of plant species in riparian areas treated for knotweed
in the Chehalis Basin of Washington.
Collaborators: The Nature Conservancy, Chehalis Basin Knotweed Project
U.S. Fish and Wildlife Service, Western Washington Fish and Wildlife Office
Knotweed Leaf Litter Decomposition
Leaf litter inputs from riparian plants are an important source of
nutrients and organic matter for aquatic organisms in small streams.
When the riparian vegetation changes from diverse native plants to
a monoculture of knotweed the quantity, quality, and timing of these
inputs is altered and may negatively affect aquatic insects and fish.
Our objectives are to examine the nutrient and decomposition properties
of knotweed leaf litter as compared to native species, along with the
aquatic fungi and macroinvertebrates utilizing the leaf litter.
Collaborators: Dr. Carri LeRoy, The Evergreen State College
Debris Flows and Stream Biota Recovery
Climate change models for the Pacific Northwest predict more
extreme climatic events. Therefore, our understanding of natural
biotic recovery from major disturbances is important. In December
2007, a rain-on-snow event triggered large-scale debris flows
down two adjacent streams in Capitol State Forest, WA, removing
all riparian vegetation. We are monitoring stream temperatures,
fish and amphibian abundances, fish movement, aquatic insect
assemblages, and riparian vegetation succession before and
after the debris flows.
Collaborators: Washington Department of Fish & Wildlife Habitat Program
Macroinvertebrates and Dam Removal
Hemlock Dam, in the Gifford Pinchot National Forest, was removed
from Trout Creek during the summer of 2009 in order to improve habitat,
productivity, and passage for fish. The intent of this study is to monitor
the impacts of dam removal and stream channel restoration on benthic
macroinvertebrate assemblages of Trout Creek upstream and downstream
of the removed dam. Certain macroinvertebrates are sensitive to
environmental stress and thus are representative of stream health.
Link: Gifford Pinchot National Forest