Stream salinization is associated with reduced taxonomic, but not functional diversity in a riparian plant community

Abstract

Dryland salinity presents an overwhelming threat to terrestrial and aquatic habitats in Australia, and yet there remains very little empirical evidence of the impacts of secondary salinization on the biodiversity of riparian communities. Here we describe the response of a riparian plant community to stream and soil salinization, 25 years after the experimental clearing of a catchment in south-western Australia. Riparian plant species diversity was inversely related to soil salinity, and plant species composition was significantly altered by increased soil salinity. Despite the evidence for an impact of salinization on the taxonomic diversity and composition of the riparian plant community, there was little evidence for any effect of salinization on functional group diversity, or on ecological functioning, as measured by the percentage of above-ground plant cover.

Colonization of Ephemeral Water Bodies in the Wheatbelt of Western Australia by Assemblages of Mosquitoes (Diptera: Culicidae): Role of Environmental Factors, Habitat, and Disturbance

“…Nevertheless, we found secondary salinization was signiÞcantly associated with changes in the composition of the habitat of water bodies. Our study supports others, which have found relationships between terrestrial, riparian, and aquatic vegetation and salinity (Cramer and Hobbs 2002;Davis et al 2003;Lymbery et al 2003;Pinder et al 2004Pinder et al , 2005Strehlow et al 2005;Doupé et al 2006;Seddon et al 2007), such as the replacement of grasses and rushes, in fresh water areas, with salt tolerant succulents such as Sarcocornia sp. in saline areas (Lymbery et al 2003).…”

“…As water bodies become saline, there are direct physiological effects on biota (Patrick and Bradley 2000, James et al 2003, Hassell et al 2006. Habitat in secondary salinized ecosystems is simpliÞed, and both salinity and habitat are likely to have a cumulative effect on the occurrence of other organisms (Davis et al 2003, Doupé et al 2006, Lyons et al 2007). Our study has found both direct (salinityÐmos-quito) and indirect (salinityÐ environment/habitatÐ mosquito) associations between the disturbance of secondary salinization and the abundance of mosquitoes.…”

“…Salinity and its effects on habitat (Lymbery et al 2003, Doupé et al 2006, Lyons et al 2007, however, inßuence the composition of mosquito communities leading to a dominance of Ae. camptorhynchus, a known vector of RRV, in saline areas.…”

“…Secondary salinity in the Western Australia Wheatbelt is known to create novel environmental conditions in water bodies, particularly to aquatic ßora , Cale et al 2004, Doupé et al 2006, Lyons et al 2007, and changes in populations of mosquitoes have also been documented (Jardine et al 2008a, Carver et al 2009b). Jardine et al (2007) postulated that secondary salinity may inßuence the ecology of Ross River virus (RRV; Togoviridae: Alphavirus) in the Wheatbelt, by promoting dominance of mosquito communities by the halotolerant vector Aedes camptorhynchus Thomson.…”

“…Disturbance of the environment, which is often anthropogenic and chronic in nature, can create novel environmental conditions, which may have direct and indirect effects on colonizing organisms (Pappas and Pappas 1983, Taniguchi and Tokeshi 2004, Benstead et al 2005, Doupé et al 2006, Lacoul and Freedman 2006, Woodcock et al 2007, Yee and Willig 2007. Populations of mosquitoes (Diptera: Culicidae) are known to respond to a range of environmental conditions, including disturbance, which can have direct or indirect effects on their colonization events (Chase and Knight 2003, Williams 2006, Carver et al 2009b).…”