Articles | Volume 11, issue 24
Biogeosciences, 11, 7331–7347, 2014
Biogeosciences, 11, 7331–7347, 2014

Research article 19 Dec 2014

Research article | 19 Dec 2014

Contrasting photosynthetic characteristics of forest vs. savanna species (Far North Queensland, Australia)

K. J. Bloomfield1,*, T. F. Domingues2,**, G. Saiz3,***, M. I. Bird4, D. M. Crayn5, A. Ford6, D. J. Metcalfe6, G. D. Farquhar1, and J. Lloyd7,8,* K. J. Bloomfield et al.
  • 1Division of Plant Sciences, Research School of Biology, The Australian National University, Canberra, ACT 2601, Australia
  • 2Universidade de São Paulo, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, São Paulo, Brazil
  • 3Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Garmisch-Partenkirchen, Germany
  • 4School of Earth and Environmental Sciences and Centre for Tropical Environmental and Sustainability Science, James Cook University, Cairns, Queensland, Australia
  • 5Australian Tropical Herbarium and Centre for Tropical Biodiversity and Climate Change, James Cook University, Cairns, Queensland, Australia
  • 6CSIRO Ecosystem Sciences Tropical Forest Research Centre, Atherton, Queensland, Australia
  • 7Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, SL5 7PY, UK
  • 8School of Marine and Tropical Biology and Centre for Tropical Environmental and Sustainability Science, James Cook University, Cairns, Queensland, Australia
  • *previously at: School of Geography, University of Leeds, Leeds, LS2 9JT, UK
  • **previously at: School of Geosciences, University of Edinburgh, Edinburgh, EH8 9XP, UK
  • ***previously at: School of Geography & Geosciences, University of Saint Andrews, Saint Andrews, KY16 9AL, UK

Abstract. Forest and savanna are the two dominant vegetation types of the tropical regions with very few tree species common to both. At a broad scale, it has long been recognised that the distributions of these two biomes are principally governed by precipitation and its seasonality, but with soil physical and chemical properties also potentially important. For tree species drawn from a range of forest and savanna sites in tropical Far North Queensland, Australia, we compared leaf traits of photosynthetic capacity, structure and nutrient concentrations. Area-based photosynthetic capacity was higher for the savanna species with a steeper slope to the photosynthesis ↔ nitrogen (N) relationship compared with the forest group. Higher leaf mass per unit leaf area for the savanna trees derived from denser rather than thicker leaves and did not appear to restrict rates of light-saturated photosynthesis when expressed on either an area or mass basis. Median ratios of foliar N to phosphorus (P) were relatively high (>20) at all sites, but we found no evidence for a dominant P limitation of photosynthesis for either forest or savanna trees. A parsimonious mixed-effects model of area-based photosynthetic capacity retained vegetation type and both N and P as explanatory terms. Resulting model-fitted predictions suggested a good fit to the observed data (R2 = 0.82). The model's random component found variation in area-based photosynthetic response to be much greater among species (71% of response variance) than across sites (9%). These results suggest that, on a leaf-area basis, savanna trees of Far North Queensland, Australia, are capable of photosynthetically outperforming forest species at their common boundaries.

Final-revised paper