title: Photosynthetic rates in relation to leaf phosphorus content in pioneer versus climax tropical rainforest trees.
abstract: In Guyana dense rainforest occurs on intensely weathered acid soils, low in soil phosphorus. To investigate whether low P availability limits photosynthesis of trees growing on these soils more than N does, leaf P and N content, and their relationship with the photosynthetic capacity (Asat, μmol CO2m-2s-1) were studied for nine pioneer and climax tree species in a range of light climates. Light environment was described using hemispherical photographs. For both pioneer and climax species, leaf P content (r2=0.71 and 0.23, respectively) is a more important determinant of Asatthan leaf N content (r2=0.54 and 0.12, respectively). Pioneer species have a higher leaf P and N content than climax species. At similar P or N content, pioneers have a higher Asatthan climax species. The saplings studied had a relatively high Asat, considering their low P concentration (15-30 μmol P g-1). All species studied had a constant leaf P and N concentration and photosynthetic capacity across light climates, because specific leaf mass (g m-2) increased similarly with light availability. This acclimation to a change in light environment makes a possible limitation of Asatby P or N independent of light environment.
authors.affiliation: Department of Plant Ecology and Evolutionary Biology, Utrecht University, P.O. Box 800.84, 3508 TB, Utrecht, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Raaimakers
authors.affiliation: Tropenbos Office, Lot 12E Garnettstreet, Campbellville, Georgetown, Guyana.
authors.forename: R G A
authors.initials: RG
authors.lastname: Boot
authors.affiliation: AB-DLO, P.O. Box 14, 6700 AA, Wageningen, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: Dijkstra
authors.affiliation: AB-DLO, P.O. Box 14, 6700 AA, Wageningen, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Pot
keywords: Climax tree species; Phosphorus Photosynthesis; Pioneer tree species; Tropical rainforest