The survival of individuals in the experiment was generally high.
The lowest number of survivors was 21 out of the 30 initial individuals
in L. major at 30 ◦C, but in all other treatments between 26
and 30 individuals survived. The effects of temperature and light
on the surviving individuals of each species are shown in Fig. 1 and
analyzed by two-way ANOVA (Table 2).
In E. densa the RGR was highest at the intermediate temperature
and this effect was strongest in the high light treatment.
Photosynthetic rates increased with temperature and the effect was
highest in the low light availability. At high light the root DW constituted
a higher proportion of the total DW in low compared to
high temperatures whereas root allocation was unaffected by temperature
at low light availability. Stem length was longest in the low
light availability and this effect was strongest at the intermediate
temperature. Number of branches increased with increased temperature
but only under the high light. Lateral spread and branching
degree increased with light and lateral spread also increased with
temperature.
For E. canadensis RGR was higher at 25 ◦C than 20 ◦C and 30 ◦C,
and much higher at 50% compared to 25% light (Fig. 1, Table 2). Photosynthetic
rate increased with temperature but more in the low
than high light treatment. At 50% light the root DW relative to total
DW decreased with temperature but not at 25% light where allocation
to roots was much lower than at 50% light. For stem length,
lateral spread, and branching degree there was no temperature
effect but a strong light effect. However, number of branches was
affected by temperature, with highest number of branches at low
temperature.
For L. major RGR and root weight ratio was highest at low temperature
but only at 50% light whereas in low light these parameters
peaked at 25 ◦C (Fig. 1, Table 2). The photosynthetic rates increased
with temperature in the 50% light treatment but in the 25% light
treatment were lower at the highest temperature. Stem length
decreased with temperature and was unaffected by light. Number
of branches and lateral spread decreased with both light and
temperature, whereas branching degree only decreased with light.
Chlorophyll content did not differ significantly between species
at either light availabilities, but was higher in the high-light treatment
(5.28 mgChl a g DW−1 ±
1.15) than the low light treatment
(9.40 mgChl a g DW−1 ±
1.22; t-test, t =
−7.36, p < 0.001).