Why is plant-growth response to elevated CO2 amplified when water is limiting, but reduced when nitrogen is limiting? A growth-optimisation hypothesis
- 1 January 2008
- journal article
- research article
- Published by CSIRO Publishing in Functional Plant Biology
- Vol. 35 (6), 521-534
- https://doi.org/10.1071/fp08128
Abstract
Experimental evidence indicates that the stomatal conductance and nitrogen concentration ([N]) of foliage decline under CO2 enrichment, and that the percentage growth response to elevated CO2 is amplified under water limitation, but reduced under nitrogen limitation. We advance simple explanations for these responses based on an optimisation hypothesis applied to a simple model of the annual carbon–nitrogen–water economy of trees growing at a CO2-enrichment experiment at Oak Ridge, Tennessee, USA. The model is shown to have an optimum for leaf [N], stomatal conductance and leaf area index (LAI), where annual plant productivity is maximised. The optimisation is represented in terms of a trade-off between LAI and stomatal conductance, constrained by water supply, and between LAI and leaf [N], constrained by N supply. At elevated CO2 the optimum shifts to reduced stomatal conductance and leaf [N] and enhanced LAI. The model is applied to years with contrasting rainfall and N uptake. The predicted growth response to elevated CO2 is greatest in a dry, high-N year and is reduced in a wet, low-N year. The underlying physiological explanation for this contrast in the effects of water versus nitrogen limitation is that leaf photosynthesis is more sensitive to CO2 concentration ([CO2]) at lower stomatal conductance and is less sensitive to [CO2] at lower leaf [N].Keywords
This publication has 77 references indexed in Scilit:
- The response of photosynthesis and stomatal conductance to rising [CO2]: mechanisms and environmental interactionsPlant, Cell & Environment, 2007
- Optimal Photosynthetic Characteristics of Individual Plants in Vegetation Stands and Implications for Species CoexistenceAnnals of Botany, 2004
- What have we learned from 15 years of free‐air CO2 enrichment (FACE)? A meta‐analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2New Phytologist, 2004
- Atmospheric CO2 elevation has little effect on nitrifying and denitrifying enzyme activity in four European grasslandsGlobal Change Biology, 2004
- Evolutionarily Stable Leaf Area Production in Plant PopulationsJournal of Theoretical Biology, 2002
- Effects of Elevated Co2 and Nitrogen Fertiliser on Biomass Productivity, Community Structure and Species Diversity of a Semi–Natural Grassland in IrelandBiology and Environment: Proceedings of the Royal Irish Academy, 2002
- Self-shading, carbon gain and leaf dynamics: a test of alternative optimality modelsOecologia, 1999
- Interactions between elevated CO2 concentration, nitrogen and water: effects on growth and water use of six perennial plant speciesPlant, Cell & Environment, 1998
- Rice responses to drought under carbon dioxide enrichment. 2. Photosynthesis and evapotranspirationGlobal Change Biology, 1997
- Optimal leaf area indices in C3 and C4 mono‐ and dicotyledonous species at low and high nitrogen availabilityPhysiologia Plantarum, 1995