CSIRO Publishing blank image blank image blank image blank imageBooksblank image blank image blank image blank imageJournalsblank image blank image blank image blank imageAbout Usblank image blank image blank image blank imageShopping Cartblank image blank image blank image You are here: Journals > Australian Journal of Botany   
Australian Journal of Botany
Journal Banner
  Southern Hemisphere Botanical Ecosystems
blank image Search
blank image blank image
blank image
  Advanced Search

Journal Home
About the Journal
Editorial Structure
Online Early
Current Issue
Just Accepted
All Issues
Special Issues
Turner Review Series
Sample Issue
For Authors
General Information
Submit Article
Author Instructions
Open Access
Awards and Prizes
For Referees
Referee Guidelines
Review an Article
Annual Referee Index
For Subscribers
Subscription Prices
Customer Service
Print Publication Dates

blue arrow e-Alerts
blank image
Subscribe to our Email Alert or RSS feeds for the latest journal papers.

red arrow Connect with us
blank image
facebook twitter LinkedIn

red arrow PrometheusWiki
blank image
Protocols in ecological and environmental plant physiology


Article << Previous     |     Next >>   Contents Vol 58(7)

The ratio of foliar nitrogen to foliar phosphorus: a determinant of leaf attributes and height in life-forms of subtropical and tropical plant communities

Ray L. Specht A C, Alison Specht B

A Emeritus Professor of Botany, The University of Queensland, 107 Central Avenue, St Lucia, Qld 4067, Australia.
B Program Manager, Terrestrial Ecosystem Research Network, The University of Queensland, Queensland 4072, Australia.
C Corresponding author. Email: r.specht@uqconnect.net
PDF (370 KB) $25
 Export Citation


In the species-rich overstorey of tropical and subtropical closed-forests (rainforests), a series of life-forms (emergent trees, canopy trees, subcanopy trees, mid-stratum trees and shrubs, interlaced with lianes) of increasing basal area, height and foliage attributes (leaf area, leaf specific weight and internode length) develop in equilibrium with aerodynamic fluxes (frictional, thermal, evaporative ± atmospheric salinity) in the atmosphere as it flows turbulently over and through a plant community. In both closed-forest and open-forest communities in eastern Australia, the translocation of high-energy nitrogen and phosphorus compounds into developing leaves – during the driest season of the year – increases as soil water becomes more available in the climatic gradient from the subhumid to the per-humid zone. Foliage attributes (leaf area and leaf specific weight) of vertical shoots are determined by the rate of input of high-energy compounds into developing shoot apices. Increasing nutrient input in the transpiration stream results in a greater number of leaves (with similar leaf specific weights) on vertical foliage shoots. The leaf area index of the tree is thus enhanced and leads to increased biomass, basal area and height at maturity. In each life-form within a closed-forest, the size of the root system is allometrically related to aboveground attributes. The ability of the root system to explore available nitrogen and phosphorus stored in the surface soil thus determines the attributes of developing foliage shoots in each of these life-forms. Both leaf areas and leaf specific weights decrease from maxima in canopy trees to leaves of subcanopy and mid-stratum trees in the milder climate under the dense structure of per-humid rainforests. In contrast, in the open-structured, subhumid rainforests, although leaf areas decrease in the gradient from canopy to mid-stratum trees – all exposed to direct solar radiation – leaf specific weights increase as temperatures in the boundary layer around growth-apices increase. The production of nitrate ions in soil, exposed to solar radiation in gaps, increases the uptake of nitrogen into leaves of pioneer trees. Larger and thinner leaves, with higher foliar N : P ratios and nitrate reductase activity, result in and enable rapid regeneration of the rainforest.

Subscriber Login

Legal & Privacy | Contact Us | Help


© CSIRO 1996-2015