Plant Establishment from the Seed Bank of a Degraded Floodplain Wetland: A Comparison of Two Alternative Management Scenarios

Abstract

There has been little research examining the soil seed banks of degraded floodplain wetlands and their contribution to wetland rehabilitation in Australia. Our aim was to assess the establishment of plants from the seed bank that may occur following the delivery of an environmental water allocation to Kanyapella Basin, a 2950 ha wetland located on the floodplain of the Goulburn and Murray Rivers in northern Victoria, Australia. Two hypothetical water regimes were investigated (flooded and dry) in a glasshouse experiment, where plants were left to establish from the seed bank over a period of 124 days. Differences in the establishment of plants from the seed bank indicated that the return of a flooding regime is likely to have a significant effect on the composition of the wetland vegetation. Mapping of the distribution of plant species indicated that propagules were highly dispersed across the wetland for the majority of taxa, in contrast to the localised distribution of many of the plant species represented in the extant vegetation. Inundation favoured the establishment of native wetland and floodplain plants, although many areas of Kanyapella Basin that are currently 'weed-free' have the potential to become colonised and potentially dominated by introduced plants if the wetland is not managed appropriately. Overall, results supported the aim of management to reestablish a wetting and drying regime through use of an environmental water allocation. This study presents a significant example of the application of seed bank investigations in wetland ecology and management.

Alterations in flood frequency increase exotic and native species richness of understorey vegetation in a temperate floodplain eucalypt forest

“…A previous spatial analysis (Robertson and James 2007) in the Kanyapella Basin (approximately 6 km south-east of Barmah forest) compared soil seed bank composition and distribution to extant wetland plant communities, concluding that seeds for most taxa were highly spatially dispersed, in contrast to the more localised distribution of many plant species in the extant vegetation. Such results indicate that seed dispersal is not limiting establishment and community composition is filtered by the spatial and temporal distribution Mean % cover of J. ingens Fig.…”

“…Increased representation of exotic flora in soil seed banks may alter the composition of regenerating plant communities following floods. Recent studies that assess seed banks of degraded floodplain wetlands in Australia to determine their contribution to wetland rehabilitation (Casanova and Brock 2000;Nias et al 2003;Nicol et al 2003;Robertson and James 2007;Williams et al 2008) collectively report establishment of exotic species during dry phases of the flooding cycle. An appropriately timed flood of sufficient depth and duration may eliminate the ability of exotic annuals to germinate and/or establish.…”

Composition of soil seed banks in southern California coastal sage scrub and adjacent exotic grassland

“…Bars indicate standard error after disturbance. Such management efforts will be greatly influenced by the state of the soil seed bank and therefore, must incorporate analysis of these seed banks to determine appropriate actions (Major and Pyott 1966;van der Valk and Pederson 1989;Fahnestock et al 2003;Hesse et al 2007;Robertson and James 2007).…”

Plant species richness in ephemeral and perennial reaches of a dryland river

“…This distribution may develop because Xood Xows broadly disperse seeds within river corridors, homogenizing species pools (Johansson et al 1996;Goodson et al 2003;Jansson et al 2005;Boudell and Stromberg 2008b), or because of episodic in situ seed production during very wet conditions. Precipitation and stream Xow are highly variable through time in desert environments, and the diVering meteorological and hydrological conditions trigger germination of diVerent assemblages of species from soil seed banks (Nicol et al 2003;Robertson and James 2007;Capon 2007). Several hydric, mesic and xeric species persisted at the perennial sites of Cienega Creek during the dry season, and additional species in all these groups established in seasons with moderate rains and Xoods.…”