ecological modelling 199 ( 2 0 0 6 ) 421–432 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ecolmodel Modelling dynamics of managed tropical rainforests—An aggregated approach Britta Tietjen a,b,* , Andreas Huth a a UFZ Centre for Environmental Research Leipzig-Halle, Department of Ecological Modelling, P.O. Box 500 136, D-04301 Leipzig, Germany b Potsdam University, Research Group Plant Ecology and Nature Conservation, P.O. Box 60 15 53, 14415 Potsdam, Germany article info Article history: Published on line 1 August 2006 Keywords: Aggregation Differential equation Forest model Genetic algorithm Logging Tropical rainforest abstract The overuse of rainforests in the last century and its consequences necessitate a rethinking of logging policies. To this end models have been developed to simulate rainforest dynamics and to allow optional management strategies to be evaluated. Parameterisation of presently existing models for a certain site needs a lot of work, thus the parameterisation effort is too high to apply the models to a wide range of rainforests. Hence, in this paper we introduce the simplified model FORREG using the knowledge we have gained from a more complex model, FORMIX3-Q. The FORREG model uses differential equations to determine the volume growth of three successional species groups. Parameterisation is simplified by a genetic algorithm, which determines the required internal model parameters from characteristics of the forest dynamics. The new model is employed to assess the sustainability of various logging policies in terms of yield and damage. Results for three forests are discussed: (1) the tropical lowland rain forest in the Dera- makot Forest Reserve, (2) the Lambir National Park in Malaysia and (3) a subtropical forest in Paraguay. Our model reproduces both undisturbed forest dynamics and dynamics of logged forests simulated with FORMIX3-Q very well. However, the resultant volumes of yield and damage differ slightly from those gained by FORMIX3-Q if short logging cycles are simu- lated. Choosing longer logging cycles leads to a good correspondence of both models. For the Deramakot Forest Reserve different logging cycles are compared and discussed. © 2006 Elsevier B.V. All rights reserved. 1. Introduction Sustainable management has been widely discussed during the last decade as one key strategy for reducing the ongoing depletion and destruction of tropical rain forests. Different certification systems have since been established to eval- uate whether a forest management practice is sustainable (Mendoza and Prabhu, 2000). One option that has been proposed towards sustainable management and decreasing logging damage is ‘reduced- ∗ Corresponding author. Tel.: +49 331 977 1938; fax: +49 331 977 1948. E-mail address: tietjen@uni-potsdam.de (B. Tietjen). impact’ logging. This involves the detailed planning and supervision of logging operations combined with special timber transport systems (e.g. skyline yarding, Kleine and Heuveldop, 1993). Empirical studies have shown that such logging methods have positive effects on the conservation of biodiversity and the stability of yields in the short-term (Pinard and Putz, 1996; Pulkki, 1997; Putz et al., 2001). Nev- ertheless, tropical forest field studies only cover a period of a few years, up to a few decades at best. To assess the sustain- ability of management, we need to know about the long-term 0304-3800/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolmodel.2005.11.045