Effects of a large flood on woody vegetation along the regulated Missouri River, USA

Abstract

In 2011, a large, long‐duration flood occurred on the regulated Missouri River following six decades without flooding. This study evaluated the effects of the flood on riparian forest structure and composition. In 2012, 168 forest sites sampled in 2006–2009 were resampled on five floodplain segments between Montana and Missouri, with 80 sampled again in 2013–2014. Changes in riparian forest area over 2006–2012, by age class and segment, were assessed using aerial imagery and GIS. Repeated‐measures analysis of variance was used to examine (a) the initial effects of the flood (preflood to 2012) on tree and shrub stem densities, (b) postflood (2012–2014) changes in stem density, and (c) species‐level responses for cottonwood (Populus deltoides), eastern red cedar (Juniperus virginiana), and Russian olive (Elaeagnus angustifolia). Across the study area, forest area declined 6–38% among age classes, with the greatest declines in the youngest classes. Tree density declined 19–49% across segments from preflood to 2012 but did not change significantly from 2012 to 2014. Shrub density declined 52–89% across segments from preflood to 2012, with 73–78% declines in the two youngest age classes, but increased by 42% from 2012 to 2014. Cottonwood and Russian olive, but not red cedar, showed partial recovery in the shrub/sapling layer, increasing from 2012 to 2014. Although flooding is important for floodplain forest health, the 2011 flood had mixed effects, with significant mortality of native floodplain trees and shrubs and only limited cottonwood recruitment. The initial decline in invasive species (Russian olive and red cedar), however, suggests that flooding may be an effective management tool.

Analysing the influence of a large flood on eastern redcedar (Juniperus virginiana) distribution along the Missouri River using remote‐sensing techniques

“…Greene and Knox (2014) observed redcedar mortality on flooded lower surfaces, whereas there were healthy redcedar individuals on non‐flooded upper surfaces. Boever et al (2019) reported a mixture of dead and live individual redcedars on many riverine forest sites after the flood within the study area. Aside from the visual observations by Greene and Knox (2014) and the stand‐based estimates of redcedar declines by Dixon et al (2015) and Boever et al (2019), there has been no comprehensive assessment of the effects of the 2011 flood on redcedar within the Missouri River floodplain.…”

“…This flood was different from pre‐regulation floods because of its exceptionally long duration, as some locations were inundated for more than 3 months (e.g., June to September) (Dixon et al, 2015) (Figure 2 inset). As a result, the flood killed a significant proportion of redcedar and Russian‐olives within the floodplain (Boever, Dixon, Johnson, Scott, & Malloy, 2019; Dixon et al, 2015; Greene & Knox, 2014). Greene and Knox (2014) observed redcedar mortality on flooded lower surfaces, whereas there were healthy redcedar individuals on non‐flooded upper surfaces.…”

Satellite View of Vegetation Dynamics and Drivers Over Southwestern China

“…One is that factors cannot be explained by climate variables are classified into human factors by RESTREND. Therefore, fires, floods, pests and diseases that cause vegetation dynamic could be mistaken for human activities (Liu et al 2013;Boever et al 2019;Yuan et al 2017). Another is RESTREND cannot detect human activities which driving vegetation throughout the study period.…”

Short‐term geomorphological and riparian vegetation responses to a 40‐year flood on a braided, dryland river

“…Asterisks indicate significant differences before and after the flood, for a given type of plot, following a mixed model (p < .05). Sediments were not analyzed in any of the reset plots changes to plant composition in unregulated (e.g., Renöfält et al, 2007;Stromberg et al, 1993) and regulated rivers (Boever, Dixon, Johnson, Scott, & Malloy, 2019;Dixon et al, 2015).…”