SCALING FROM TREES TO FORESTS: TRACTABLE MACROSCOPIC EQUATIONS FOR FOREST DYNAMICS

Authored by Nikolay Strigul, Denis Pristinski, Drew Purves, Jonathan Dushoff, Stephen Pacala

Date Published: 2008

DOI: 10.1890/08-0082.1

Sponsors: No sponsors listed

Platforms: SORTIE

Model Documentation: Other Narrative Mathematical description

Model Code URLs: Model code not found

Abstract

Individual-based forest simulators, such as TASS and SORTIE, are spatial stochastic processes that predict properties of populations and communities by simulating the fate of every plant throughout its life cycle. Although they are used for forest management and are able to predict dynamics of real forests, they are also analytically intractable, which limits their usefulness to basic scientists. We have developed a new spatial individual-based forest model that includes a perfect plasticity formulation for crown shape. Its structure allows us to derive an accurate approximation for the individual-based model that predicts mean densities and size structures using the same parameter values and functional forms, and also it is analytically tractable. The approximation is represented by a system of von Foerster partial differential equations coupled with an integral equation that we call the perfect plasticity approximation (PPA). We have derived a series of analytical results including equilibrium abundances for trees of different crown shapes, stability conditions, transient behaviors, such as the constant yield law and self-thinning exponents, and two species coexistence conditions.

Tags

Age Growth-model Crown asymmetry Field-measurements Plant-populations Pinus-sylvestris Size-structure Physiological processes Community structure Local competition