Disentangling the Formation of Contrasting Tree-Line Physiognomies Combining Model Selection and Bayesian Parameterization for Simulation Models

Authored by Thorsten Wiegand, Isabel Martinez, Camarero J Julio, Enric Batllori, Emilia Gutierrez

Date Published: 2011

DOI: 10.1086/659623

Sponsors: European Union Spanish Ministries

Platforms: No platforms listed

Model Documentation: ODD Mathematical description

Model Code URLs: Model code not found

Abstract

Alpine tree-line ecotones are characterized by marked changes at small spatial scales that may result in a variety of physiognomies. A set of alternative individual-based models was tested with data from four contrasting Pinus uncinata ecotones in the central Spanish Pyrenees to reveal the minimal subset of processes required for tree-line formation. A Bayesian approach combined with Markov chain Monte Carlo methods was employed to obtain the posterior distribution of model parameters, allowing the use of model selection procedures. The main features of real tree lines emerged only in models considering nonlinear responses in individual rates of growth or mortality with respect to the altitudinal gradient. Variation in tree-line physiognomy reflected mainly changes in the relative importance of these nonlinear responses, while other processes, such as dispersal limitation and facilitation, played a secondary role. Different nonlinear responses also determined the presence or absence of krummholz, in agreement with recent findings highlighting a different response of diffuse and abrupt or krummholz tree lines to climate change. The method presented here can be widely applied in individual-based simulation models and will turn model selection and evaluation in this type of models into a more transparent, effective, and efficient exercise.

Tags

Dynamics population Climate-change Forest Spatial-patterns Chain monte-carlo Multicriteria assessment Seedling recruitment Spanish central pyrenees Pinus-uncinata