Abundance and composition of plant species along grazing gradients in Australian rangelands

Abstract

Summary1. The widespread provision of livestock drinking water in previously dry Australian rangelands has supported concomitant increases in cumulative grazing pressure. While the associated impacts on plants of pastoral importance have been well documented, far less is known about the rest of the flora. 2. To address this deficiency, we measured the frequency of occurrence of all plant species at sites along water-centred grazing gradients in commercial paddocks located in the rangelands of central and southern Australia. Four gradients were in chenopod shrubland vegetation, and four in acacia woodlands. Each gradient extended to a reference site remote from all waters, where grazing by stock was minimal. Five further sites were sampled along each gradient, at locations progressively closer to the gradient's watering point. 3. Ground-layer species far outnumbered those in upper layers (466 and 134, respectively). Most were geographically localized (72% found at one gradient only) and locally uncommon (46% per gradient occurred with a frequency < 5% per site). 4. Species showing trends of decreasing frequency with proximity to water significantly outnumbered those showing increasing trends. Significantly more species that were recorded only once occurred at the sites furthest from water, where long-term grazing pressure was least. Some gradients also showed an overall decline in species richness with increasing proximity to water. 5. Most species were native, and among these there were no clearly identifiable 'global winners' (i.e. no widespread species advantaged by grazing and associated disturbances). In contrast, the majority of the few exotic species, including two of the three most widespread species found, showed increasing abundance with proximity to watering points. 6. Synthesis and applications. The results from this study indicate consistent and substantial changes in plant composition that are probably related to the accumulated long-term impacts of water-centred grazing. The consequences are potentially severe, because artificial watering points are now extremely widespread in the Australian rangelands. Identification and protection of representative, water-remote refugia for the most grazing-sensitive species should therefore be a high priority for regional conservation.

Anthropogenic dust emissions due to livestock trampling in a Mongolian temperate grassland

“…2a). Many studies proved that livestock density (i.e., grazing pressure) is usually highest close to water sources or settlements and decreases with distance away from such localities (Andrew and Lange, 1986;FernandezGimenez and Allen-Diaz, 2001;Landsberg et al, 2003;Sasaki et al, 2008;Cheng et al, 2011). According to Stumpp et al (2005) the livestock spatial densities were higher in the first 300 m of the transects from the local centers.…”

Ecosystem structure, function and composition in rangelands are negatively affected by livestock grazing

“…These included measures of species diversity, taxon richness, diversity, similarity, abundance, and frequencies of different biota. These measures again are known to be correlated and are widely used in studies investigating the impacts of livestock grazing (Landsberg et al 2003). The attribute function is concerned with the fluxes of energy and matter within ecosystems.…”

Meeting the ecological challenges of agricultural change: editors’ introduction

“…Here, even small changes, for example the provision of stock-watering or stock-holding facilities, can have disproportionate ecological consequences (Landsberg et al . 2002(Landsberg et al . , 2003Riginos & Hoffman 2003).…”

“…These papers illustrate the coverage of comparative agricultural ecology across global regions and ecosystems in the Journal of Applied Ecology, for example ranging from North American forest wetlands (Middleton 2003), through riparian wetlands in mainland Europe (Clément et al 2003;Kleijn & Sutherland 2003), conventional farmlands in the British Islands (Hutton & Giller 2003;Wickramasinghe et al 2003) to rangelands in Australia (Landsberg et al 2003). These papers illustrate effects related to agriculture not only directly in the farmed landscape, but also in changes and processes involving hydrological run-off through riparian zones and into the open waters that receive agricultural drainage (Clément et al 2003;Wickramasinghe et al 2003).…”

“…Perhaps most of all, these seven papers illustrate very effectively the array of approaches used by applied ecologists in addressing agricultural questions including modelling (Stephens et al 2003), meta-analysis Ecological Society, Journal of Applied Ecology, 40, 939-946 (Kleijn & Sutherland 2003), surveys (Wickramasinghe et al 2003), transect studies (Landsberg et al 2003), experiments (Hutton & Giller 2003), seedbank assays (Middleton 2003) and process studies based on modern ecological methods (Clément et al 2003). In so doing, the papers in this special profile reconfirm the role of the Journal of Applied Ecology in showcasing and developing some of the best methods currently available for problem solving in ecology.…”