17th December – FIFWA Newsletter 1 National Story

Retired firefighter and current Chair of the Friends of Wellington Discovery Forest, Don Spriggins has decades of expert experience in forest management in south west WA and shares his thoughts on the ABC article that links the recent devastating Queensland fires to climate change.

The Wellington Discovery Forest is a “One stop Shop” for people to increase their knowledge and understanding of the jarrah forest. There are long-term vegetation monitoring plots to observe and measure the impacts of this reducing rainfall trend, and growth plots to measure the increased diameter growth rates of thinned stands and the increase in leaf area.

Many experienced foresters reject the notion of blaming every serious bushfire on climate change and using it as an excuse for failed land management. One factor Don is certain that contributes to higher bushfire risk and intensity since rainfall started declining in the mid 1970s, is the reduced moisture content in live trees, understorey, ground vegetation and the soil profile, at least in the jarrah forest. Much of this is due to overcrowding, or a heavily stocked forest. This can be managed to some extent through thinning, or reducing the number of relatively small stemmed trees, which reduces overcrowding and competition.

The impact of drought deaths and reduced water in the soil increases the chances of scrub and understorey species also collapsing, as well as becoming more inflammable in summer. The jarrah/marri forest tries to reduce transpiration loss by shedding more leaves. All of this increases the fuel load on the ground, all with a much lower moister content compared to pre 1975 conditions. When a drier year than the average comes along, drought deaths become common as these overstocked stands start to collapse.

Below are some words directly from Don:

Wellington Discovery Forest and Fire Impact Observations

The 684 hectare Wellington Discovery Forest located on the headwaters of the Ferguson River catchment was first established in 1992 and later gazetted in 2004 as a special reserve for the purpose of education, research, and management of the jarrah forest. At the time, many people in the community were arguing that all native forests in the South West should be National Parks and any management intervention excluded.

As with many popular ideas, what is popular is not necessarily the best path to follow. Two things are essential for a healthy jarrah forest, regular fuel reduction about every five years to minimise the impact of intense summer bushfires and reducing (also known as thinning) the highly overstocked forest for the reduced rainfall being received today. Rainfall decline in the South West started in 1975 and so far shows no sign of stopping. Drought deaths of jarrah trees and understorey plants is now a common occurrence closer to Perth in low rainfall years. Metropolitan dams now contribute little to Perth’s water supplies and irrigation dams in the South West are commonly only partially full.

Other evidence that overstocked, (unthinned) jarrah forest is starved of water is the observation both in the January 2016 Waroona bushfire and a 2013 bushfire that burnt a small section at the Discovery Forest, that few of the trees burnt in these fires did not produce epicormics shoots but remained stone dead. Normally after a summer fire (e.g. the 1961 Dwellingup Fire), most jarrah trees although defoliated by the fire, produce epicormic shoots and new leaves within a few months.

Mild prescribed burn WDF

Mild fuel reduction burn to minimise the effect of intense summer bushfires.

2015-16 thinning WDF

Recently thinned stand at Wellington Discovery Forest in 2015-16, taken not long after thinning.

2017 post thining WDF

The same area taken in 2017. Note the increase in tree crown size and extra leaves.

Apart from National Parks where thinning is prohibited, thinning of jarrah stands in the northern jarrah forest, i.e. State Forest and removal and sale of the non-mill log residue would have a positive benefit for fire management as well as drought-proofing the jarrah forest.

Don Spriggins

 

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