Impacts of flooding on successional species turnover in restored floodplain wetlands (presentation)

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Restoration is often described in terms of facilitating or accelerating natural succession. Assumed successional patterns, such as increasing species richness and a temporal shift in plant community dominance from annual to perennial species, are borne out across a variety of plant community types including many wetlands. Vegetation change occurs rapidly in the first few years following major disturbance, land abandonment or restoration, but the initially rapid rates of species turnover and colonization by new species predictably decrease over successional time. Decreasing colonization rates can be caused by competition from previously established plants and the increasingly limited availability of microsites for germination, and because as sites age and species richness increases, an increasing proportion of the incoming propagules are from species that have already established at the site. Despite these regular trends, successional trajectories may be erratic in frequently disturbed habitats like floodplains. We investigated the effects of flood exposure and time since restoration on annual rates of plant species colonization and local extinction in 20 restored floodplain wetlands. Vegetation was surveyed in each site for 4 to 8 consecutive years, and a flood exposure index was calculated from continuous hydrologic data for each site and year. Annual rates of species loss were unrelated to time since restoration but increased significantly in years with greater flood exposure. Up to 46% of the plant species were lost from sites in years with major flood disturbances. Years with high flood exposure coincided with increased losses of both annual and perennial plant species and both hydrophytes and non-hydrophytes. Of these groups, non-hydrophytes had local extinction rates that were most strongly accelerated by increasing flood exposure. As expected based on previous successional studies, annual colonization by new species was highest in recently restored wetlands and generally declined with time since restoration. However, colonization rates of annuals and non-hydrophytes also increased the year following major a flood year, contributing to a rapid recovery of species richness after disturbance. Although colonization by new species tends to decrease as sites age, suggesting stabilization, restoration trajectories can be difficult to predict in frequently disturbed ecosystems. Floods temporarily decrease plant species richness by removing many species, especially those species more typical of uplands. Rapid colonization after floods, however, possibly due to the input of propagules via hydrochory and the creation of suitable sites for germination and establishment, maintains resilience in the successional trajectories of restored floodplain wetlands.
Original languageEnglish (US)
Title of host publication9th INTECOL International Wetlands Conference: Wetlands in a Complex World
Subtitle of host publicationConference Abstracts
PublisherInternational Association for Ecology
StatePublished - 2012
Event2012 INTECOL International Wetlands Conference: Wetlands in a Complex World - Orlando, United States
Duration: Jun 3 2012Jun 8 2012
Conference number: 9


Conference2012 INTECOL International Wetlands Conference
Country/TerritoryUnited States


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