It is assumed that trees and plants maximize their growth rate by optimally adjusting tissue nitrogen concentrations, leaf area index, and fine root biomass. Based on this principle, forest responses to elevated CO2 , soil nutrient availability and other factors can be explained.

Key results and conclusions so far :

• The model could explain forest productivity and LAI responses to elevated CO2 in four face experiments
• The role of soil nutrient availability in limiting forest CO2 responses was explained in general and for the Duke and Oak Ridge FACE sites.
• The optimiality theory and/or related ecological principles has the potentail to improve and simplify vegetation modelling

Publications:

Dewar RC, Franklin O, Mäkelä A, Mcmurtrie RE, Valentine HT. 2009. Optimal Function Explains Forest Responses to Global Change. BioScience 59: 127-39.

Franklin O, McMurtrie RE, Iversen CI, Crous KY, Finzi AC, Tissue DT, Ellsworth DS, Oren R, Norby RJ. 2009. Forest fine-root production and nitrogen use under elevated CO2: Contrasting responses in evergreen and deciduous trees explained by a common principle. Global Change Biology 15, 132–144.

Franklin O. 2007. Optimal nitrogen allocation controls tree responses to elevated CO2. New Phytologist 174: 811–822.

Franklin O, Högberg P, Ekblad A, Ågren G I. 2003. Pine forest floor carbon accumulation in response to N and PK additions – Bomb 14C modelling and respiration studies. Ecosystems 6: 644-658.

Ågren G I, Franklin O. 2003. Root:shoot ratios, optimisation and nitrogen productivity. Annals of Botany 92: 795-800.

Franklin O. 2003. Plant and Forest Dynamics in Response to Nitrogen Availability. Doctoral thesis, Silvestria 285, Swedish University of Agricultural Sciences. (summary)

Franklin O, Ågren G I. 2002. Leaf senescence and resorption as mechanisms of maximizing photosynthetic production during canopy development at N limitation. Functional Ecology 16: 727-733