 Abstract | Tree clearing is practised for greater beef production and hence monetary gains from grazing
systems of central Queensland. The high rates of clearing in the past and even recently (577,
000 ha/yr during 1999-2001) were mainly to develop land for pastures. The sustainability of
cleared pasture systems over the long-term is questioned.
Three major types of tree communities i.e. Eucalyptus populnea F. Muell., E. melanophloia F.
Muell. and Acacia harpophylla F. Muell. ex. Benth. were selected on one property in central
Queensland to quantify the impacts of clearing on pasture production and composition, and
soil properties. The impacts were measured over time-since-clearing (recent (<5 years),
medium (11-13years) and old (>30 years)) in unreplicated cleared pastures in comparison to
their replicated uncleared/intact woodland pastures of each tree community.
Measures of pasture above-ground biomass production on a single property over time-sinceclearing
in cleared systems showed that gains were not sustained over the long-term. The
difference in response to clearing between tree communities was evident and important to
support the future policy decisions. The impact of clearing on soil properties (physicochemical
and biological) was confirmed, and explained the lesser availability of nutrients with
time of clearing in cleared pastures. The changes in some soil properties underscored the
associated risks and changes in ecosystem functions due to clearing. Less litter was produced
at cleared than uncleared pastures, but nutrient release was faster at cleared compared to
uncleared systems. The overall effect of clearing in terms of pasture and litter production, and
major soil parameters were analysed using multivariate analyses. |
