Riparian Soil Development Linked to Forest Succession Above and Below Dams Along the Elwha River, Washington, USA

Perry, Laura G.; Shafroth, Patrick B.; Perakis, Steven S.

doi:10.1007/s10021-016-0080-1

Cited by 9 publications

(13 citation statements)

References 112 publications

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“…The changes in plant community composition across landforms were correlated with flood‐associated environmental variables. Bar plots had relatively more sand and gravel, and larger particle sizes, whereas terrace plots had finer soil texture, more litter, and higher total exchange capacity, consistent with previous findings along the Elwha River (Perry et al, 2017).…”

Section: Discussionsupporting

confidence: 89%

Does large dam removal restore downstream riparian vegetation diversity? Testing predictions on the Elwha River, Washington, USA

Brown

Thomas

Cubley

et al. 2022

Ecological Applications

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Large dams and their removal can profoundly affect riparian ecosystems by altering flow and sediment regimes, hydrochory, and landform dynamics, yet few studies have documented these effects on downstream plant communities.Ecological theory and empirical results suggest that by altering disturbance regimes, reducing hydrochory, and shifting communities to later successional stages, dams reduce downstream plant diversity. Dam removal could reverse these processes, but the release of large volumes of sediment could have unexpected, transient effects. Two large dams were removed on the Elwha River in Washington State, USA, from 2011 to 2014, representing an unprecedented opportunity to study large dam removal effects on riparian plant communities.

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Section: Discussionsupporting

confidence: 89%

Does large dam removal restore downstream riparian vegetation diversity? Testing predictions on the Elwha River, Washington, USA

Brown

Thomas

Cubley

et al. 2022

Ecological Applications

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“…However, plantavailable inorganic N pools and N transformation rates measured in soil during the peak growing season immediately prior to the annual return of salmon were largely unaffected by salmon enhancement. Indeed, the 20 yr of cumulative salmon N additions in the zone near the stream in our study (~6690 kg N/ha) greatly exceeded typical riparian surface soil N pools (500-2500 kg N/ha; Walker 1989, Morris and Stanford 2011, Perry et al 2017, suggesting that even partial retention of salmon N inputs in soils should have increased soil [N org ]. Given numerous conventional long-term fertilization experiments worldwide have shown a consistent pattern of elevated soil inorganic N pools and N transformations (H€ ogberg et al 2006(H€ ogberg et al , Lu et al 2010, it was surprising that 20 yr of MDN inputs did not clearly accelerate soil N cycling in our study.…”

Section: Discussionmentioning

confidence: 65%

“…Soils are the dominant (>70%) sink for added N in forests worldwide (Templer et al 2012), and tree growth in high-latitude conifer forests is often strongly N-limited (Nordin et al 2001), both of which should have fostered retention of salmon N inputs to our site. Indeed, the 20 yr of cumulative salmon N additions in the zone near the stream in our study (~6690 kg N/ha) greatly exceeded typical riparian surface soil N pools (500-2500 kg N/ha; Walker 1989, Morris and Stanford 2011, Perry et al 2017), suggesting that even partial retention of salmon N inputs in soils should have increased soil [N org ]. The lack of increase in soil [N org ] due to salmon that we observed is consistent with the lack of increase in N availability, because soil [N org ] fuels long-term , Table 1) for ½NH þ 4 and ½NO À 3 , net mineralization and nitrification, [N org ], and gravimetric water content for both the salmon-enhanced and the salmon-depleted banks of Hansen Creek at 1, 3, 6, 10, and 20 m from the edge of the creek bed with 95% confidence intervals (dashed line) for predicted values.…”

Section: Discussionmentioning

confidence: 67%

Riparian soil nitrogen cycling and isotopic enrichment in response to a long‐term salmon carcass manipulation experiment

et al. 2019

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Pacific salmon acquire most of their biomass in the ocean before returning to spawn and die in coastal streams and lakes, thus providing subsidies of marine-derived nitrogen (MDN) to freshwater and terrestrial ecosystems. Recent declines in salmon abundance have raised questions of whether managers should mitigate for losses of salmon MDN subsidies. To test the long-term importance of salmon subsidies to riparian ecosystems, we measured soil nitrogen cycling in response to a 20-yr manipulation where salmon carcasses were systematically removed from one bank and deposited on the opposite bank along a 2km stream in southwestern Alaska. Soil samples were taken at different distances from the stream bank along nine paired transects and measured for organic and inorganic nitrogen concentrations, and nitrogen transformation rates. Marine-derived nitrogen was measured using 15 N/ 14 N for bulk soils, and NH þ 4 and NO À 3 soil pools. Stable isotope analyses confirmed 15 N/ 14 N was elevated on the salmon-enhanced bank compared to the salmon-depleted bank. However, 15 N/ 14 N values of plant-available inorganic nitrogen exceeded the 15 N/ 14 N of salmon inputs, highlighting nitrogen isotope fractionation in soils that raises significant methodological issues with standard MDN assessments in riparian systems. Surprisingly, despite 20 yr of salmon supplementation, the presence of MDN did not cause a long-term increase in soil nitrogen availability. This finding indicates the importance of MDN to ecosystem nitrogen biogeochemistry, and riparian vegetation may be overestimated for some systems. Given that essential nutrients can also be pollutants, we urge more critical analyses of the role of MDN to inform compensatory mitigation programs targeting salmon nutrient enhancement.

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“…Overstory Thuja also occurred in 20% of plots, mainly in stands >90 years old but sometimes in relatively young stands 34–55 years old, unlike the findings of Stolnack and Naiman (), because they did not examine forests along the lower segment where almost all of the Thuja we observed were located. Higher soil calcium and magnesium in the lower segment may have contributed to higher Thuja abundance (Hawkins and Robbins ; Perry et al., in press).…”

Section: Discussionmentioning

confidence: 99%

Effects of dams and geomorphic context on riparian forests of the Elwha River, Washington

et al. 2016

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Abstract. Understanding how dams affect the shifting habitat mosaic of river bottomlands is key for protecting the many ecological functions and related goods and services that riparian forests provide and for informing approaches to riparian ecosystem restoration. We examined the downstream effects of two large dams on patterns of forest composition, structure, and dynamics within different geomorphic contexts and compared them to upstream reference conditions along the Elwha River, Washington, USA. Patterns of riparian vegetation in river segments downstream of the dams were driven largely by channel and bottomland geomorphic responses to a dramatically reduced sediment supply. The river segment upstream of both dams was the most geomorphically dynamic, whereas the segment between the dams was the least dynamic due to substantial channel armoring, and the segment downstream of both dams was intermediate due to some local sediment supply. These geomorphic differences were linked to altered characteristics of the shifting habitat mosaic, including older forest age structure and fewer young Populus balsamifera subsp. trichocarpa stands in the relatively static segment between the dams compared to more extensive early-successional forests (dominated by Alnus rubra and Salix spp.) and pioneer seedling recruitment upstream of the dams. Species composition of later-successional forest communities varied among river segments as well, with greater Pseudotsuga menziesii and Tsuga heterophylla abundance upstream of both dams, Acer spp. abundance between the dams, and P. balsamifera subsp. trichocarpa and Thuja plicata abundance below both dams. Riparian forest responses to the recent removal of the two dams on the Elwha River will depend largely on channel and geomorphic adjustments to the release, transport, and deposition of the large volume of sediment formerly stored in the reservoirs, together with changes in large wood dynamics.

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Riparian Soil Development Linked to Forest Succession Above and Below Dams Along the Elwha River, Washington, USA

Cited by 9 publications

References 112 publications

Does large dam removal restore downstream riparian vegetation diversity? Testing predictions on the Elwha River, Washington, USA

Does large dam removal restore downstream riparian vegetation diversity? Testing predictions on the Elwha River, Washington, USA

Riparian soil nitrogen cycling and isotopic enrichment in response to a long‐term salmon carcass manipulation experiment

Effects of dams and geomorphic context on riparian forests of the Elwha River, Washington

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