Rangelands Management and Fire Ecology

Flashcards covering rangeland management, the history of fire use in Australia, woody thickening, and specific fire management strategies for pasture and conservation.

How long have traditional owners managed the Australian continent through the use of fire?

For 60,000 years or more (approximately 1,000 generations).

What is an "obligate fire germinator"?

A species of plant whose seeds will not germinate unless they have been exposed to fire.

What characterizes the "mosaic" of burn patterns seen in historical photos of the Great Sandy Desert?

Different areas burned at different time points over cycles of years or decades, creating patches with varied fuel loads and vegetation ages.

What term describes the increased density and size of native and introduced woody species observed since colonial settlement?

Woody thickening.

What three factors have likely contributed to woody thickening in the last 50 years?

Higher rainfall, increasing atmospheric $CO_2$ from greenhouse gas emissions, and the removal of traditional fire management.

How did early European explorers describe the landscape of the Australian interior, such as Chinchilla?

As "park-like" open woodland grassland, managed to prevent trees from touching and competing for space.

In resource-marginal rangelands, how do trees contribute to soil nutrition?

Through leaf fall, which cycles nutrients like nitrogen and phosphorus from above-ground biomass into the topsoil and subsoil.

What is a major economic impact of woody thickening on grazing systems?

It reduces sustainable carrying capacities due to trees and shrubs outcompeting grasses.

How does woody thickening increase the risk of losing mature trees during a fire?

It accumulates high fuel loads that allow fires to burn hot and high into the canopy, whereas open grasslands only support low-intensity grass fires that leave mature trees unharmed.

How does grazing typically influence the balance between trees and grasses?

Grazing tends to suppress grasses (which ruminants evolved to eat) in favor of trees, unless browsing animals like goats are used.

How do perennial tussock grasses protect themselves from fire?

Their structure serves an insulating role to protect the base of the plant and the roots from excessive heat.

How does fire management help favor 3P grasses over undesirable wiregrass?

Wiregrass seeds remain on the soil surface and are susceptible to fire, while seeds of 3P grasses like black spear grass are often buried and protected in the soil.

When is the optimal time to burn if the management objective is "improved pasture quality"?

The early wet season (spring), to ensure immediate rainfall supports the regrowth of high-quality vegetative material.

What is the primary target for fire when managing woody weeds?

Smaller saplings and suckers, typically those less than $1.5\,m$ high.

What is the recommended frequency for burning to effectively manage woody weeds?

Approximately every four years, to catch regrowth before it exceeds the height and tolerance of fire.

How do Savannah burning projects earn carbon credits via the Emissions Reduction Fund?

By implementing cool fires early in the dry season to reduce fuel loads, thereby preventing intense, high-emission wildfires late in the dry season.

Why is the early wet season considered the lowest-risk time to burn for most production objectives?

Rainfall has begun, which reduces fire intensity and allows plants to immediately regenerate and regrow.

What characteristic allows fire-tolerant Australian trees to regenerate after their leaves are scalded?

Epiphytic growth, where new leaves sprout directly from the branches and trunks rather than just the tips.

How does fire assist in managing "patch grazing" in large rangeland paddocks?

It removes rank, low-quality senescent material and stimulates fresh, palatable regrowth, which attracts livestock to previously under-utilized areas.

What is the minimum fuel load required to support a hot burn capable of killing trees?

Approximately $2,000\,kg/ha$ of dry matter.

How does dry season protein supplementation indirectly promote woody thickening?

By increasing the animal's intake, it reduces the available biomass (fuel load), resulting in fires that are too cool to kill woody weeds.