Event Title

Resilience of novel riparian forests of the regulated Missouri River

Presenter Information

Malia Volke
W. Carter Johnson

Location

USU Eccles Conference Center

Event Website

www.restoringthewest.org

Abstract

Cottonwood forest regeneration has sharply declined along the Missouri River and other western U.S. rivers due primarily to flow regulation by dams. Novel river habitats, including delta formations where tributaries empty into reservoirs, are one of the few places along the Missouri River where there is successful cottonwood regeneration. The delta formed at the confluence of the White River and Fort Randall Reservoir in South Dakota represents such a novel habitat. Time-series analysis of riverine cross-sections indicated that there has been a trend of channel and floodplain aggradation within the postdam delta, facilitating expansion of delta surfaces into and above the reservoir pool. Likewise, time-series analysis of aerial photography showed that forest area increased by 69 percent in the postdam era. Field inventories determined that a heterogeneous mixture of cottonwood forests exists within the White River delta region, and that the composition and structure of these forests differs from those along natural river reaches. Although there has been an overall trend of increasing forest area, turnover of forest patches is common, especially for patches at the lowest elevations vulnerable to prolonged reservoir inundation. Flooding of the expanding delta has increased over the last two decades and is likely to become more typical in the future due to climate change and ageing of the reservoir system, including formation of larger deltas and reduced reservoir storage capacity. Knowledge of the existing vegetation patterns and morphology of the White River delta can reveal how reservoir pools could be managed to favor the expansion and survival of delta forests over the long-term.

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Oct 16th, 12:55 PM Oct 16th, 1:00 AM

Resilience of novel riparian forests of the regulated Missouri River

USU Eccles Conference Center

Cottonwood forest regeneration has sharply declined along the Missouri River and other western U.S. rivers due primarily to flow regulation by dams. Novel river habitats, including delta formations where tributaries empty into reservoirs, are one of the few places along the Missouri River where there is successful cottonwood regeneration. The delta formed at the confluence of the White River and Fort Randall Reservoir in South Dakota represents such a novel habitat. Time-series analysis of riverine cross-sections indicated that there has been a trend of channel and floodplain aggradation within the postdam delta, facilitating expansion of delta surfaces into and above the reservoir pool. Likewise, time-series analysis of aerial photography showed that forest area increased by 69 percent in the postdam era. Field inventories determined that a heterogeneous mixture of cottonwood forests exists within the White River delta region, and that the composition and structure of these forests differs from those along natural river reaches. Although there has been an overall trend of increasing forest area, turnover of forest patches is common, especially for patches at the lowest elevations vulnerable to prolonged reservoir inundation. Flooding of the expanding delta has increased over the last two decades and is likely to become more typical in the future due to climate change and ageing of the reservoir system, including formation of larger deltas and reduced reservoir storage capacity. Knowledge of the existing vegetation patterns and morphology of the White River delta can reveal how reservoir pools could be managed to favor the expansion and survival of delta forests over the long-term.

http://digitalcommons.usu.edu/rtw/2013/Poster/1