Effects of light and nutrients on seedlings of tropical Bauhinia lianas and trees
Z.-Q. Cai (1, 2, 3), L. Poorter (2, 4), Q. Han (5) and F. Bongers (2)
1. Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, P.R. China / 2. Forest Ecology and Forest Management Group, Centre for Ecosystem Studies, Wageningen University, P.O. Box 47, 6700 AA Wageningen,
The Netherlands / 3. Corresponding author () / 4. Resource Ecology Group, Centre for Ecosystem Studies, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands / 5. Department of Plant Ecology, Forestry and Forest Products Research Institute (FFPRI), Ibaraki 305-8687, Japan / Received July 2, 2007; accepted February 20, 2008; published online June 2, 2008
Summary
Lianas differ from trees in many life history characteristics, and we predicted that they are phenotypically more responsive
to environmental variation than trees. We analyzed responsiveness to light and nutrient availability of five Bauhinia species (three lianas and two trees). Seedlings were grown in a shade house in two light regimes (5 and 25% of full sunlight)
and two nutrient supply regimes (field soil and N fertilization equivalent to 100 kg ha–1), and important growth-related physiological and morphological plant parameters were measured. Light availability affected
most of the measured variables, whereas N addition had only weak effects. In the four light-demanding species (two lianas
and two trees), relative plant biomass growth rate increased and specific leaf area (SLA) decreased with increased light availability,
whereas a shade-tolerant liana did not respond. Leaf N concentration and light-saturated photosynthetic rate per unit leaf
area increased in response to increased irradiance or soil N in the light-demanding tree species and the shade-tolerant liana,
but not in the two light-demanding lianas. The light-demanding lianas also had higher SLA and leaf mass ratio, resulting in
a higher leaf area ratio (LAR) in high light, whereas the light-demanding trees did not. Across all treatments, mean plasticity
indices of physiological and morphological traits, and all traits combined were similar among the studied species. Plasticity
was higher in response to light than to N, indicating that light is the main factor controlling seedling responses of the
studied species. Although lianas and trees did not differ in mean plasticity in response to light and N, the light-demanding
lianas were phenotypically less plastic in LAR and in photosynthetic rates and biomass allocation than the trees. Light and
N interacted in their effects on most physiological variables, but the consequences for relative growth rate differed little
among species. We conclude that, contrary to our predictions, lianas were no more responsive to variation in light and N availability
than trees.
