Technical highlights - Department of Primary Industries ...

Part 1 Integrated weed management
1. Understanding grader grass (Themeda quadrivalvis) ecology for improved management
Project dates
July 2006 – June 2015
Project leader
Dr Wayne Vogler
Tropical Weeds Research Centre
Tel: (07) 4761 5707
Email: wayne.vogler@deedi.qld.gov.au
Other staff in 2010–11
Laura Roden
Objectives
• Examine the effect of fire frequency
and timing on grader grass biomass
and overall pasture composition.
• Quantify the seed longevity of grader
grass.
Rationale
Management of invasive grasses has
received little attention compared to
research undertaken on other exotic
weeds. There is a general lack of
understanding of appropriate control
options, particularly ones that are
economical to apply over large areas
of low-value land and in areas of high
conservation value.
Grader grass (Themeda quadrivalvis)
has the potential to change biodiversity,
reduce conservation values and reduce
grazing-animal production over large
areas of the tropical savannas. The
Queensland Government Department of
Environment and Resource Management
(DERM) has identified this as a
critical conservation issue threatening
biodiversity in national parks. Also,
the pest management plans of several
local governments identify the weed as
a significant threat both economically
and environmentally; the Mitchell River
Watershed Management Group classifies
it as a significant weed species.
This project aims to explain some basic
ecological aspects of grader grass in
response to management and natural
conditions, so that management
recommendations are based on science
rather than anecdotal evidence.
Methods
Effect of fire frequency and timing
In a replicated plot trial we impose each
treatment (fire during dry season, fire
at start of wet season, fire at end of
wet season) at yearly, two-yearly and
four-yearly intervals. For comparison,
we also apply the herbicide paraquat
(concentration of 250 g L –1 ) at 2 L ha –1
prior to seed set at yearly intervals.
Changes in pasture species and biomass
composition are measured using the
Botanal methodology.
Progress in 2010–11
Seed longevity
Artificial seed-bank trials were
completed in 2010. For the final results,
see Technical highlights 2009–10.
Photo 1.1 Grader grass dominates a yearly burn plot at Undara National Park, 2011
Photo 1.2 Perennial grass dominates a herbicide plot at Undara National Park, 2011
Part 1 Integrated weed management 3