Mitchell grass death in Queensland: extent, economic impact and potential for recovery

Citation

Land & Water Australia. 2007. Mitchell grass death in Queensland: extent, economic impact and potential for recovery . [Online] (Updated June 10th, 2008)
Available at: http://lwa.gov.au/node/7 [Accessed Sunday 21st of March 2010 07:23:10 AM ].

Summary

Mitchell grass is an important economic resource for graziers in western Queensland. Mitchell grasslands have seen a marked decline in condition across large areas. Queensland Department of Primary Industries & Fisheries (DPI&F) researcher David Phelps and colleagues are working with Queensland graziers to assess the extent and economic impact of Mitchell grass dieback and to devise recovery strategies. Funding for the research is joint initiative of Meat & Livestock Australia and Land, Water & Wool. The research is on-going but at this stage management of tillers during and after drought seems to be of key importance.

Aims

Following nearly 5000 field assessments, a comprehensive information kit for graziers and their advisors has been developed. The kit will also be integrated in the EDGEnetwork™ Grazing Land Management Extension module. The kit recommends strategies such as wet season spelling, delayed re-stocking and reduced stock numbers to help restore pasture health and maximise productivity as quickly as possible. Importantly, early grazing of drought affected tillers reduces seed supply and energy reserves in the plant’s roots. On the other hand, deferred grazing of drought affected tillers allows it to complete its lifecycle, so that it can continue to supply energy to the tussock, produce seed and serve as a point for more tillers to grow along its stem.

Preliminary analysis of relationship between rainfall, grazing and burning regimes on the survival of Mitchell grass tussocks and pastures has been undertaken while a rapid assessment procedures for use by landholders have also been established.

The project has resulted in better understanding of the ecological requirements of Mitchell grass and accordingly, a better understanding of how it should be managed. Healthier stands of Mitchell grass are leading to better production, improved landscape function (for example, in terms of reducing wind erosion) and better drought resilience. Mac Drysdale, from ‘Perola Park’ near Augathella in Queensland, is one of the landholders guiding the project. Mac says that the real value of the project is in focussing the grazier’s attention on the resources and productivity of his or her land – “It’s an important homing of your skills that is imperative to the long-term viability of grazing.”

Specific key findings are as follows:

Economic modelling estimates that, for four Shires in Central-West Queensland alone, loss of production could climb as high as $15 million per year due to the decline in land condition associated with Mitchell grass death.
Soil seed bank samples collected and analysed to date have revealed low levels of Mitchell grass seed present, which suggests that recovery from the latest drought will be slow.
Anecdotal evidence suggests that fire and grazing management affect Mitchell grass growth after drought but this is still under investigation.

Outcomes

By mid-2007, the project aims to:

Estimate the geographic extent of poor pasture condition, especially in relation to death, or ‘dieback’ of Mitchell grass plants;
Assess the impact of dieback on the profitability of enterprises; and
Encourage and assist graziers to restore pastures to good condition and begin to understand how to improve management during future droughts.

Background

Mitchell grasslands represent 19 per cent of Queensland’s native pasture area and support more than 40 per cent of the State’s Merino sheep flock and 10 per cent of the beef cattle herd.

During the 2001-04 drought, large areas of Mitchell grass tussocks died primarily through extended moisture stress and possibly grazing of young sweet growth. The most severely affected area is the Central West of Queensland - in the affected areas, tussock mortality is estimated to be as high as 90 per cent across entire properties. For these areas to recover, Mitchell grass density will have to increase through seedling recruitment.

This project was conducted by Queensland Department of Primary Industries & Fisheries (DPI&F) and managed by Meat & Livestock Australia (MLA), with Australian Wool Innovation (AWI) (through Land & Water Australia as manager of Land Water & Wool) as a contributor. MLA will continue to mange the project beyond the life of Land, Water & Wool.