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Raised litter traps underneath 7-year-old E.
gunni plantation, south-east Queensland
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Leaf fall and total monthly rainfall in
7-year-old subtropical eucalypt plantations, south-east Queensland.
Error bars show variation between species. (March rainfall is
incomplete: only for week three onwards)
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HemiView image of E. gunni plantation
(stand has been pruned and thinned)
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In forests, the exchange of carbon and water between the
atmosphere and the soil is driven by canopy leaf area, its turnover
and its distribution in space and time. Mila Bristow, a
postdoctoral research scientist, and her Queensland colleagues have
been investigating these factors and related forest processes such
as crown architecture and decomposition in subtropical plantations
near Gympie in Queensland.
An important part of transferring our understanding of temperate
and Mediterranean forest systems to the tropics and subtropics is
to understand the processes that allow us to establish parameters
and apply predictive models like CABALA and 3PG. There are
differences in absolute values, as well as seasonality, of
temperature and rainfall in these northern environments compared
with the better understood southern environments. This means that
plant architectural characteristics as well as processes such as
foliage turnover and decomposition are likely to be quite
different.
We have been tracking monthly litter fall and decomposition and
comparing this to climatic conditions in Eucalyptus
dunnii, E. cloeziana and Corymbia citriodora
subsp. variegata plantations near Gympie in southern
Queensland. Analyses from the initial six months of this
study indicate that monthly rainfall is driving canopy dynamics as
less leaf litter falls in the months in which there is greater
total rainfall.
To complement our measures of leaf litter fall, we are examining
hemispherical canopy photos with Greg Unwin from the University of
Tasmania. Greg’s photos allow us to describe the light
environment in these eucalypt plantations with digital estimation
and modelling of leaf area index (LAI), radiation load, canopy and
subcanopy light description. In March 2008 HemiView data confirmed
that C. citriodora subsp. variegata has an LAI
less than half that of E. dunnii. Measurements were
repeated in December, and will be taken again in March 2009. The
results will help us to address questions about efficiency of
resource capture and allocation for these species.
Dr Mila Bristow
Postdoctoral Research Fellow, Project 1.4
Tel: 07 5482 0865
Mila.Bristow@dpi.qld.gov.au
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