Transcript sheffels_limno

Potential Invasive Plant
Establishment After Dam Removal:
A Case Study of the Elwha River Dams
Trevor Sheffels
November 25, 2009
Outline
• Background
– Dam removal in the United States
– Invasive plant establishment
• Research on invasions after dam removal
• Case Study
– History of the Elwha River
– Potential invasive plant establishment
Outline
• Background
– Dam removal in the United States
– Invasive plant establishment
• Research on invasions after dam removal
• Case Study
– History of the Elwha River
– Potential invasive plant establishment
Dam Removal in the United States
• Majority of dams are nearing
end of licensing agreements
• Approximately 500 dams
have been removed in the
last decade
• Pacific Northwest is
prominent in dam removal
discussions due to salmon
migration issues
Importance to Limnology
• Conversion from
manmade lentic
reservoirs to natural lotic
rivers
• Dam removal completely
alters watershed
biogeochemical
processes
• Large-scale disturbance
that results in variety of
ecosystem impacts
Invasive Plant Establishment
• Invasive species are often
found in disturbed habitats
(Elton 1958)
• Invasive plants are often
pioneer species
• Life history strategies
allow invasive plants to
outcompete native species
Outline
• Background
– Dam removal in the United States
– Invasive plant establishment
• Research on invasions after dam removal
• Case Study
– History of the Elwha River
– Potential invasive plant establishment
Invasions After Dam Removal
• Resident seed bank can
contain viable invasive species
seeds (Nishihiro and Washitani
2007)
DAM
REMOVAL
• Natural revegetation of
exposed reservoir can be
prone to invasive species
(Auble et al. 2007)
• Natural hydrology results in
new source of invasive species
introduction downstream
(Gurnell et al. 2006)
Exposed
seed bank
Lake bed
colonization
Downstream
transport
Outline
• Background
– Dam removal in the United States
– Invasive plant establishment
• Research on invasions after dam removal
• Case Study
– History of the Elwha River
– Potential invasive plant establishment
Elwha River
Dams
• Watershed covers
20% of Olympic
National Park
• Two hydroelectric
dams constructed in
early 1900s
• Native salmon
habitat has been
severely restricted
Glines Canyon and Elwha Dams
• Glines Canyon Dam
– 210 feet tall
– Lake Mills reservoir
covers 415 acres
• Elwha Dam
– 108 feet tall
– Lake Aldwell reservoir
covers 267 acres
Reservoir Bed Seed Banks
• Seed bank is trapped
mostly in fine sediment
• 50% of Lake Mills seed
bank is viable (Brown and
Chenoweth 2008)
• 15% of these seeds are
invasive species (Brown
and Chenoweth 2008)
Exposed Sediment
• 18 million cubic yards of
accumulated sediment in two
reservoirs (Mussman et al. 2008)
• 13 invasive species are present
and likely to establish (Brown
unpublished)
• Initial establishment could result
in long-term problems (Orr and
Stanley 2006)
Invasive Species Downstream
• Large quantity of
sediment will move
downstream over short
period of time (Mussman
et al. 2008)
• Natural levels of
hydrochory will be
restored (Brown and
Chenoweth 2008)
• Establishment of natural
stream banks may be an
issue
Conclusions
• Invasive species establishment should be
considered when considering tradeoffs of dam
removal
• Processes are not well-understood and further
research is needed
• Elwha project provides a unique opportunity to
study invasive species establishment following a
large dam removal
References
Auble, G.T., P.B. Shafroth, M. Scott, and J.E. Roelle. 2007. Early vegetation
development on an exposed reservoir: implications for dam removal.
Journal of Environmental Management 39: 806-818.
Brown, R.L. and J. Chenoweth. 2008. The effect of Glines Canyon Dam on
hydrochorous seed dispersal in the Elwha River. Northwest Science 82:
197-209.
Elton, Charles. 1958. The ecology of invasions by animals and plants.
Methuen, London, England.
Gurnell, A.M., A.J. Boitsidis, K. Thompson, and N.J. Clifford. 2006. Seed bank,
seed dispersal and vegetation cover: colonization along a newly-created
river channel. Journal of Vegetation Science 17: 665–674.
Mussman, E.K., D. Zabowski, and S.A. Acker. 2008. Predicting secondary
reservoir sediment erosion and stabilization following dam removal.
Northwest Science 82: 236-246.
Nishihiro J. and I. Washitani. 2007. Restoration of lakeshore vegetation using
sediment seed banks: studies and practices in Lake Kasumigaura, Japan.
Global Environmental Research 11: 171-177.
Orr, C.H. and E.H. Stanley. 2006. Vegetation development and restoration
potential of drained reservoirs following dam removal in Wisconsin. River
Research and Applications 22:281-295.