This experiment, part of the ‘TropAdapt’ project
(
https://tropadapt.org/) was conducted across three common garden
trials established within the Wet Tropics bioregion of far north
Queensland, Australia: two in the coastal lowlands and one in the
uplands. The first lowland site is located at the Daintree Rainforest
Observatory (DRO) in Cape Tribulation (−16.10449 °S, 145.4511 °E) with
an elevation of 52 m (a.s.l.), mean annual temperature (MAT) of 24.5 °C
and a mean annual precipitation (MAP) of 3026 mm. The soil at the site
is acidic, dystrophic, brown dermosol, formed in the colluvium from the
metamorphic and granitic mountains to the west (Murtha 1989). The second
lowland site was established on an old airstrip in Cow Bay (−16.22406
°S, 145.4220 °E) with a MAT of 24.4 °C and a MAP of 3439 mm. Although
soils in the area were originally dominated by haplic, dystrophic, red
ferrosols formed on an alluvial fan derived from basalt (Murtha 1989),
an anthropogenic reworking of the site and augmentation with sand and
gravels to form the airstrip have left the soils poorly structured. The
upland study site is in the southern Atherton Tablelands (−17.43025 °S,
145.5153 °E) on Thiaki Creek Nature Reserve
(
https://www.biome5.com.au/thiaki) at an elevation of 980 m a.s.l.
It has a MAT of 19 °C and receives a MAP of 2264 mm. The site is on a
formed from Cainozoic Basalt (Malcolm
et al. 1999). The property
was previously managed as a cattle pasture for approximately 70 years,
and subsequently used as a research site for several previous
reforestation experiments (Charles
et al. 2018) (Preece
et
al. 2015, Preece
et al. 2017). The common garden plot used for
this study is dominated by exotic grass species (e.g.
Melinis
minutiflora ,
Urochloa (
Brachiaria )
decumbens and
Setaria sphacelata ) and receives no shading from nearby trees.
The two lowland sites, DRO and Cow Bay are both located within the
Daintree Rainforest and as such are similar both geographically and
climatically. They differ primarily in soil nutrient status. The upland
site Thiaki provides a climate contrast with MAT differing by
~ 5.5 °C and MAP differing by ~ 969 mm
compared to the two lowland sites but does not suffer in terms of soil
nutrient availability like the Cow Bay site. Comparison of tree
performance across these three sites allows assessment of the effects of
both climatic (upland vs lowland sites) and edaphic factors (low
nutrient vs high nutrient sites).