Phenotypic plasticity of seedlings of five tropical tree species in response to different light and nutrient availability

Gong, H. D.

TROPICAL ECOLOGY

2016

57

4

Wang, H; Cai, ZQ

There is an ongoing debate to which extent the phenotypic plasticity is associated with the shade-tolerance of species along a broad environmental gradient. Seedlings of five species of varying shade tolerance were grown under each of the four combinations of high and low light or nutrient availabilities in shade houses. Leaf, fine root and whole-plant traits were measured to evaluate the phenotypic plasticity in seedlings of five species in response to light and nutrition gradients. Generally, leaf nitrogen and phosphorus concentrations, specific leaf area (SLA), leaf area ratio, specific fine-root length and surface area (SRL, SRSA), leaf mass ratio, and relative growth rate decreased, whereas total root mass ratio increased with increasing shade tolerance of species, indicating light-demanding species had higher ability to capture above-and below-ground resources and thus had higher growth rate than shade-tolerant species. Light was a more important limiting factor than soil nutrients for the five studied species; and the light responsiveness at different nutrient availability for most morphological variables was similar among different species. In response to light and nutrient gradients, the mean plasticity index of all variables measured did not differ significantly among the five species, indicating that the species with contrasting shade tolerance have similar plasticity. There were significantly positive correlations in leaf area (mass) and fine-root surface area (mass) for each species along light and nutrient gradients. Moreover, there were significant correlations between leaf and fine-root nitrogen and phosphorus concentrations, leaf area and fine-root surface area, SLA and SRL or SRSA across all species and treatments. Our result thus provided an evidence of a common leaf and root traits syndrome linking traits to effects on plant and ecosystem process.