Offered Papers Theme A: Efficient Production from Grassland

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Grazing of sheep in arid grasslands is risky; sudden shifts to lower functional states may occur when the ecosystem is stressed (Scheffer et al., 2001). To avoid the stresses that shift states, easy-to-recognise critical thresholds need to be identified (Westoby et al., 1989). Preliminary analysis of perennial grass survival in a drought indicated a critical threshold based on co-occurrence of drought and grazing. Crossing this threshold collapses grass populations (Hodgkinson, 1994). Here we examine the relationships between basal area change and rainfall and grazing levels based on a 10-year period and propose a management guideline.

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Sheep Grazing During Drought Collapses the Perennial Grass Resource in Australian Semiarid Wooded Grasslands

Grazing of sheep in arid grasslands is risky; sudden shifts to lower functional states may occur when the ecosystem is stressed (Scheffer et al., 2001). To avoid the stresses that shift states, easy-to-recognise critical thresholds need to be identified (Westoby et al., 1989). Preliminary analysis of perennial grass survival in a drought indicated a critical threshold based on co-occurrence of drought and grazing. Crossing this threshold collapses grass populations (Hodgkinson, 1994). Here we examine the relationships between basal area change and rainfall and grazing levels based on a 10-year period and propose a management guideline.