Predicting spread of invasive exotic plants into dewatered reservoirs after dam removal on the Elwha River, Olympic National Park, Washington

Woodward, Andrea; Torgersen, Christian E.; Chenoweth, Joshua; Beirne, Katherine; Acker, Steven A.

doi:10.3133/ofr20111048

Cited by 6 publications

(13 citation statements)

References 28 publications

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“…Colonization and spread of nonnative plants on former reservoir sediments is a common concern of resource managers. This CMC applies across various land management objectives, including protection and maintenance of natural ecosystems and species diversity (Chenoweth and Acker, ; Woodward et al ., ), or municipal‐park management (Orr and Stanley, ). However, the acceptable range of nonnative plant colonization or expansion varies with each dam‐removal case and management entity, though it is likely that most resource managers would find it unacceptable if one or a few nonnative species came to dominate a former reservoir site.…”

Section: Evaluating the Cmcsmentioning

confidence: 99%

“…These propagule sources may vary depending on surrounding land use and interact with time since removal, landform, and the direct management actions discussed above. Through surveys of nonnative plant populations in areas upstream and surrounding a dam-removal site, managers can evaluate potential nonnative plant propagule pressure prior to dam removal to help assess the likelihood of significant invasion (Woodward et al, 2011).…”

Section: Journal Of the American Water Resources Associationmentioning

confidence: 99%

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Synthesis of Common Management Concerns Associated with Dam Removal

Tullos

Collins

Bellmore

et al. 2016

J American Water Resour Assoc

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Managers make decisions regarding if and how to remove dams in spite of uncertainty surrounding physical and ecological responses, and stakeholders often raise concerns about certain negative effects, regardless of whether these concerns are warranted at a particular site. We used a dam‐removal science database supplemented with other information sources to explore seven frequently raised concerns, herein Common Management Concerns (CMCs). We investigate the occurrence of these concerns and the contributing biophysical controls. The CMCs addressed are the following: degree and rate of reservoir sediment erosion, excessive channel incision upstream of reservoirs, downstream sediment aggradation, elevated downstream turbidity, drawdown impacts on local water infrastructure, colonization of reservoir sediments by nonnative plants, and expansion of invasive fish. Biophysical controls emerged for some of the concerns, providing managers with information to assess whether a given concern is likely to occur at a site. To fully assess CMC risk, managers should concurrently evaluate site conditions and identify the ecosystem or human uses that will be negatively affected if the biophysical phenomenon producing the CMC occurs. We show how many CMCs have one or more controls in common, facilitating the identification of multiple risks at a site, and demonstrate why CMC risks should be considered in the context of other factors such as natural watershed variability and disturbance history.

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Section: Evaluating the Cmcsmentioning

confidence: 99%

Section: Journal Of the American Water Resources Associationmentioning

confidence: 99%

Synthesis of Common Management Concerns Associated with Dam Removal

Tullos

Collins

Bellmore

et al. 2016

J American Water Resour Assoc

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“…Several projects completed before dam removal suggested that native plants may be slow to colonize the newly dewatered reservoirs (Chenoweth ; Michel et al ), while invasive alien species may be rapid and abundant colonizers (Woodward et al ). Michel et al () predicted the spread of the invasive species Canada thistle ( Cirsium arvense ) on the newly exposed substrates due to its ability to thrive on infertile soils, but this has yet to be observed.…”

Section: Discussionmentioning

confidence: 99%

“…Michel et al () predicted the spread of the invasive species Canada thistle ( Cirsium arvense ) on the newly exposed substrates due to its ability to thrive on infertile soils, but this has yet to be observed. Woodward et al () expected the invasion of several other exotic species after the dam had been removed, but this too has not yet occurred. They also suggested that restoration by planting trees would facilitate bird‐dispersed invasive alien species such as Himalayan blackberry ( Rubus armeniacus ).…”

Section: Discussionmentioning

confidence: 99%

“…Ecological conditions before dam removal were thoroughly evaluated (Duda et al ). Seed rain and revegetation of the dewatered reservoirs were estimated prior to dam removal (Chenoweth ; Michel et al ; Woodward et al ). Studies immediately after the removal concerned the transport and re‐deposition of sediments (Draut & Ritchie ; East et al ; Magirl et al ), restoration of fish migration, especially for salmon (Tonra et al ; Magilligan et al ), and mycorrhizal influences (Cortese & Bunn ).…”

Section: Introductionmentioning

confidence: 99%

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Spontaneous and assisted restoration of vegetation on the bottom of a former water reservoir, the Elwha River, Olympic National Park, WA, U.S.A.

Prach

Chenoweth

Moral

2019

Restoration Ecology

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Early seral vegetation was studied on a former lake bottom after the removal of the 64-m-tall Glines Canyon Dam on the Elwha River. In 2015, vegetation cover of all vascular plant species was determined in 63 plots located on sites that emerged in 2011-2012. The sites had been planted and/or seeded, or were permitted to revegetate spontaneously. The plots were further classified by substrate texture: coarse sediments on the valley bottom and fine ones on the valley slopes. Plots were located randomly along random transects perpendicular to the former lake shore that extended into coarse sediment terraces perched above the floodplain. Additionally, 32 plots were sampled in surrounding native forests near these transects. Data were analyzed by detrended correspondence analysis and by canonical correspondence analysis. Substrate texture, that is whether fine or coarse, appeared to explain most of the variability in vegetation. The distance to forest and successional age, that is time since the site had been drained, were also significant explanatory variables, while assisted restoration by planting and seeding appeared to be insignificant to date. Spontaneous succession on fine sediments led to a species composition approaching that of adjacent natural forests. Invasive species were much less abundant than expected. Spontaneous restoration of vegetation on fine sediments in drained lake bottoms can rapidly produce a desirable vegetation composition and structure. On coarse sediments, active restoration may be useful to accelerate the development of native vegetation communities.

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Planting, seeding, and sediment impact restoration success following dam removal

Chenoweth

Bakker

Acker

2021

Restoration Ecology

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Large dam removals effectively restore geomorphic and hydrologic processes, but little is known about subsequent vegetation recovery and the role of active restoration. We studied whether planting and seeding affected vegetation recovery in a dewatered reservoir, and whether effects differed on landforms composed of fine or coarse-textured sediments. The dewatered reservoir is behind the former Glines Canyon Dam, which was removed from the Elwha River in Washington State (U.S.A.) in 2011-2014. We measured bare ground in 2013-2017, and species richness, relative frequency of non-native species, woody stem density, and species composition in 2016. Sediment texture affected all response variables. Several years after seeding, bare ground was reduced on coarse sediments and non-native species frequency was reduced on both textures. Planting increased species richness. Seeding and planting altered species composition on both textures, with stronger effects on coarse sediments. High densities of riparian woody plants naturally established on fine sediments, reaching a mean of 34,000 stems/ha 5 years after dam removal began; density was only a fraction of this (5,000 stems/ha) on coarse sediments. Future dam removals should incorporate sediment texture into their revegetation plans. Seeding and planting can be valuable strategies for minimizing nonnative species frequency, increasing species richness, and establishing desirable target species after dam removal, particularly on landforms composed of coarse sediments.

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Predicting spread of invasive exotic plants into dewatered reservoirs after dam removal on the Elwha River, Olympic National Park, Washington

Cited by 6 publications

References 28 publications

Synthesis of Common Management Concerns Associated with Dam Removal

Synthesis of Common Management Concerns Associated with Dam Removal

Spontaneous and assisted restoration of vegetation on the bottom of a former water reservoir, the Elwha River, Olympic National Park, WA, U.S.A.

Planting, seeding, and sediment impact restoration success following dam removal

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