Many grasslands in Australia are under pressure from intensive grazing by cattle and sheep. This pressure is further compounded by climate change. Drought events are predicted to become more extreme in large parts of Australia potentially altering the functioning of grasslands. To optimize grazing activities for sustainable productivity of these grasslands for the future, it is necessary to understand how different plant species cope with different grazing pressures under extreme drought events. Species that are able to conserve water and nutrients will likely respond differently to grazing and drought pressures than species that are more opportunistic and whose growth depend on quick uptake of water and nutrients after rainfall events.
In this project, the uptake of water and nutrients, as well as the internal recycling of nutrients through resorption and relocation, will be investigated for different species in a grassland exposed to different levels of simulated grazing (clipping) and drought (rainout shelters). Different strategies in water and nutrient uptake and recycling among species will then be related to their temporal stability in production. A field experiment will be conducted at John Bruce Pye Farm of the University of Sydney in Bringelly, NSW. Experimental plots will be established with different frequencies of clipping. Rainout shelters will be used to remove all rainfall during certain times of the year simulating extreme drought events.
The field experiment will be complimented with growth chamber experiments under controlled environmental conditions. Stable isotope techniques (15N, 13C) will be used in field and growth chamber experiments to examine water and nitrogen dynamics within species and at the whole plant community level.
Results from this project will help provide important information about how to adjust grazing management for maintaining sustainable productivity in Australian grasslands exposed to extreme drought events that are likely to occur more frequent in the future.
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