Australian Rangeland Systems and Grazing Management

Flashcards covering rangeland management, stocking rates, the Jones and Sandland model, and grazing strategies based on the lecture transcript.

Why are Australian rangelands considered ecologically important from an environmental perspective?

They are fragile ecosystems where natural processes dominate, and they are critical for maintaining biodiversity and acting as a carbon source due to tree density.

What has caused the considerable 'woody thickening' observed in Australian rangelands over time?

The removal of indigenous and traditional land management, specifically regular fire management, and its replacement with grazing production systems.

How is land condition assessed using the ABC D system in rangelands?

It is assessed by the coverage of three P perennial species, the level of soil degradation, and the thickening of woody weeds or shrubs.

What is the primary stocking recommendation for producers in rangeland systems?

Stocking at the long-term carrying capacity.

Why is assessing long-term carrying capacity currently considered a challenge in northern Australia?

Rainfall records from the last $30$ to $40$ years show a period of higher than average rainfall, making it difficult to determine if current carrying capacity assessments are truly sustainable for the future.

How does the Jones and Sandland model behave differently in rangelands compared to temperate systems?

In rangelands, per hectare productivity often appears to increase constantly with stocking rate rather than showing a peak and subsequent decline, masking the reality of land degradation.

Why does a short-term economic optimum stocking rate often conflict with the ecological optimum in rangelands?

Increased stocking rates may improve short-term profitability, but they degrade the land faster than livestock productivity responds, jeopardizing long-term sustainability.

According to the lecture, why doesn't scaling back stocking rate provide an immediate improvement in animal liveweight gain?

Because rangelands have a fixed and often short growing season, reducing stock during the dry season results in no immediate pasture growth or improved per-head yield.

What are the two main reasons animal productivity on a per head basis is lower in rangelands than in temperate systems?

Lower soil fertility and rainfall, along with environmental challenges like heat, parasites, and the long distances animals must walk.

What is 'patch grazing' and why is it prevalent in rangelands?

It is the selective grazing of specific areas or plants, driven by the high diversity of species, low stocking densities, and animal preference for high-quality feed.

What is the typical utilization rate of annual herbage growth in Australian rangelands?

Approximately $20\%$ to $30\%$, or as low as $10\%$ to $20\%$ for land in poorer condition.

Describe the impact of watering points on grazing distribution in a large paddock.

Cattle overutilize areas close to water, creating a radial effect of high grazing intensity near the source that decreases as distance increases.

What is a 'sacrifice zone' in the context of rangeland water sources?

The area within approximately a $500\,m$ radius of a water source where almost no feed is available due to extreme over-grazing.

Why might installing more watering points be more effective than fencing to reduce patch grazing?

It enables animals to spread out and utilize more of the landscape without reducing their ability to be selective, which is necessary for maintaining productivity.

What did research in the Douglas Daly region indicate regarding intensive rotational grazing in rangelands?

It resulted in lower productivity on a per head basis because animals were forced to eat lower quality feed due to the lack of selectivity.

Why did the lecturer suggest that Australian rangeland soils might not cope well with high-intensity rotational grazing?

Unlike systems in Africa, Australian soils did not evolve with cloven-hoofed animals and are easily disturbed, leading to potential losses in soil carbon and damage to bio-crusts.

What is 'wet season spelling' and why is it used?

It is the practice of removing stock during the wet season to allow perennials (three P species) to reach the reproductive phase, set seed, and improve land condition.

How long does it typically take to lift land condition by one ABC D class using wet season spelling?

It generally requires two back-to-back seasons of wet season spelling.