Riparian plant community responses to increased flooding: a meta‐analysis

Abstract

A future higher risk of severe flooding of streams and rivers has been projected to change riparian plant community composition and species richness, but the extent and direction of the expected change remain uncertain. We conducted a meta-analysis to synthesize globally available experimental evidence and assess the effects of increased flooding on (1) riparian adult plant and seedling survival, (2) riparian plant biomass and (3) riparian plant species composition and richness. We evaluated which plant traits are of key importance for the response of riparian plant species to flooding. We identified and analysed 53 papers from ISI Web of Knowledge which presented quantitative experimental results on flooding treatments and corresponding control situations. Our meta-analysis demonstrated how longer duration of flooding, greater depth of flooding and, particularly, their combination reduce seedling survival of most riparian species. Plant height above water level, ability to elongate shoots and plasticity in root porosity were decisive for adult plant survival and growth during longer periods of flooding. Both 'quiescence' and 'escape' proved to be successful strategies promoting riparian plant survival, which was reflected in the wide variation in survival (full range between 0 and 100%) under fully submerged conditions, while plants that protrude above the water level (>20 cm) almost all survive. Our survey confirmed that the projected increase in the duration and depth of flooding periods is sufficient to result in species shifts. These shifts may lead to increased or decreased riparian species richness depending on the nutrient, climatic and hydrological status of the catchment. Species richness was generally reduced at flooded sites in nutrient-rich catchments and sites that previously experienced relatively stable hydrographs (e.g. rain-fed lowland streams). Species richness usually increased at sites in desert and semi-arid climate regions (e.g. intermittent streams).

Higher genetic diversity in recolonized areas than in refugia of Alnus glutinosa triggered by continent‐wide lineage admixture

“…Wetland habitats are strongly endangered by recent climate changes, which influence the water supply and flooding regime, altering the distributions of many species (Erwin ; Garssen et al . ). Our study brings evidence that populations of Alnus glutinosa , a keystone species of European swamp habitats, exhibit high genetic diversity in northerly located populations due to continent‐wide admixture of different genetic lineages.…”

Early plant recruitment stages set the template for the development of vegetation patterns along a hydrological gradient

“…; Garssen et al . ) and drought (Garssen, Verhoeven & Soons ) in riparian zones. Perhaps, earlier studies focused particularly on the flooded part of the riparian zone, where seedling survival was strongly inhibited also in our experiments.…”

Impacts of Climate Change on Riverine Ecosystems: Alterations of Ecologically Relevant Flow Dynamics in the Danube River and Its Major Tributaries

“…On the other hand, many fish species can benefit from those flood and high flow events that restore river-floodplain connectivity, thus leading to an increase in abundance/biomass or enhancing recruitment [47][48][49]. Riparian plant communities are also strongly affected by the duration and depth of flooding, as revealed in a recent meta-analysis by Garssen et al [50]. The results for the indicator ∆DOY peak are evaluated as absolute changes expressed in the number of days.…”