semi-steppe rangelands are a complex, highly dynamic and often multi-layered mosaic of grassland, shrubland, and intermediate communities. a few recent studies have explicitly or implicitly developed synthetic hypotheses about how interactive effects of human made disturbances initiate dynamic changes in plant community composition to cause a shifting mosaic of vegetation pattern across the lan...

Grazing changes plant species composition of grassland ecosystems by selective removal and trampling. Grazing also alters soil physical and biogeochemical properties and can dramatically change hydrologic processes that can impact water budgets and quality. For these reasons, practical means are needed to assess grazing management practices and its impacts upon the land. This study examines whe...

Background. A large proportion of natural grasslands around the world is exposed to overgrazing resulting in land degradation and biodiversity loss. Although there is an increasing effort in the promotion of sustainable livestock management, rangeland degradation still occurs because animals' foraging behaviour is highly selective at different spatial scales. The assessment of the ecological me...

In contrast with the marine reaches of estuaries, few studies have dealt with zooplankton grazing on phytoplankton in the upper estuarine reaches, where freshwater zooplankton species tend to dominate the zooplankton community. In spring and early summer 2003, grazing by microand mesozooplankton on phytoplankton was investigated at three sites in the upper Schelde estuary. Grazing by mesozoopla...

This study focused on confirming the grazing selectivity of sheep, more and less selective, in pasture New Zealand, under two different phenological stages forage. Two experiments were conducted: 1) Comparison selective non-selective sheep irrigated with perennial ryegrass white clover. 2) A comparison was performed a high rate senescence composed ryegrass, barley barnyard grass. The botanical ...

Using the seawater dilution technique, we measured phytoplankton growth and microzooplankton grazing rates within and outside of the 1999 Bering Sea coccolithophorid bloom. We found that reduced microzooplankton grazing mortality is a key component in the formation and temporal persistence of the Emiliania huxleyi bloom that continues to proliferate in the southeast Bering Sea. Total chlorophyl...

The grazing behaviour and diet selection by Dorper sheep, as well as other related aspects (pasture intake, walking habits and trampling) is reviewed. It was clear that Dorper sheep are less-selective grazers, compared to Merino-type breeds. Dorpers utilised shrubs and bushes to a greater extent, but grass to a lesser extent in relation to Merino sheep. The Dorper also utilised a larger number ...

Although nutrient availability and oceanographic context can influence top-down processes in intertidal communities, the reciprocal effects of consumers on bottom-up processes, such as nitrogen uptake by macroalgae, are less well-documented. We used a combination of field observations, mesocosm experiments, and laboratory nitrate-uptake measurements to evaluate the interaction between the kelp ...

Decreasing body size has been suggested as the third universal biological response to global warming after latitudinal/altitudinal range shifts and shifts in phenology. Size shifts in a community can be the composite result of intraspecific size shifts and of shifts between differently sized species. Metabolic explanations for the size shifts dominate in the literature but top down effects, i.e...