Data from: Trade-offs in juvenile growth potential vs. shade tolerance among subtropical rainforest trees on soils of contrasting fertility

Plant adaptation to gradients of light availability involves a
well-studied functional trade-off, as does adaptation to gradients of
nutrient availability. However, little is known about how these two major
trade-offs interact, and thus, it remains unclear whether and how the
nature of the growth–shade tolerance trade-off differs on soils of
contrasting fertility. We asked whether juvenile growth–shade tolerance
trade-offs differed in slope and elevation between tree assemblages on
nutrient-rich basalt and nutrient-poor rhyolite soils in an Australian
subtropical rain forest. We measured the growth of, and the range of light
environments occupied by, juveniles (40–120 cm tall) of eight basalt
specialists, six rhyolite specialists, and one generalist that was common
on both substrates. In situ minimum light requirements were estimated from
the 5th percentile of the distribution of naturally regenerated juveniles
in relation to daily light transmittance. Stem growth was measured for
12–16 months across a wide range of light environments to estimate the
light compensation point of growth of each species. Light compensation
points of growth showed nearly a 1 : 1 correspondence with in situ minimum
light requirements of species, indicating that whole-plant carbon balance
is a key driver of ecological success in low light. Minimum light
requirements were negatively correlated with relative growth rate in low
light, but correlated positively with growth in high light. Soil type had
no effect on either the slope or the elevation of this trade-off, all
species aligning around a common growth–shade tolerance trade-off, but our
results do show a wider range of growth rates and shade tolerance on the
nutrient-rich basalt soil than on the nutrient-poor rhyolite. Our results
suggest that adaptation to light availability involves fundamentally
similar trade-offs on these two substrates of differing fertility.
However, a wider range of growth rates and shade tolerance on the
nutrient-rich basalt soil than on the nutrient-poor rhyolite may help to
explain the higher species richness and greater structural complexity of
forest stands on the former substrate.