Dynamics and Sustainable Use of Species-Rich Moist Forests a Process-Based Modelling Approach
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PhD Dissertation 16/2006 Dynamics and sustainable use of species-rich moist forests A process-based modelling approach Nadja Rüger Helmholtz-Zentrum für Umweltforschung GmbH – UFZ Permoserstraße 15, 04318 Leipzig Internet: www.ufz.de Phd Dissertation 16/2006 Phd Dissertation ISSN 1860-0387 Dynamics and sustainable use of species-rich moist forests A process-based modelling approach Dissertation zur Erlangung des Doktorgrades der Naturwissenschaften (Dr. rer. nat.) am Fachbereich Mathematik/Informatik der Universität Osnabrück vorgelegt von Nadja Rüger aus Weimar Osnabrück 2006 Vom Fachbereich Mathematik/Informatik der Universität Osnabrück am 30. Juni 2006 als Dissertation angenommen. Erstgutachter: Prof. Dr. Horst Malchow Zweitgutachter: Dr. habil. Andreas Huth Tag der mündlichen Prüfung: 10. November 2006 “The prerequisite for our survival and for peace among humankind is compliance with the many tolerance limits of the geo-biosphere’s dynamic stabilization, of the limits of robustness of our natural foundations of life and their regeneration cycles.” Potsdam Manifesto 2005 “We have to learn to think in a new way” Abstract Sustainable use of species-rich moist forests is hampered by an insufficient under- standing of their dynamics and long-term response to different wood harvesting strategies. This thesis contributes to a better understanding of natural forest dynamics, explores the productivity of native forests subjected to different management strategies, and quantifies the ecological impacts of these strategies. The thesis focuses on two study regions: tropical montane cloud forest (TMCF) in central Veracruz, Mexico, and Valdivian temperate rain forest (VTRF) in northern Chiloé Island, Chile. The process-based forest growth model FORMIND is applied to study natural forest succession, to assess long-term ecological implications of fuelwood extraction on TMCF, to explore the potential of secondary TMCF for provision of ecosystem services and fuelwood, and to compare potential harvesting strategies for VTRF regarding forest productivity and ecological consequences. Simulation results show that both forest types have a high potential for wood production. As wood extraction increases, the forest structure becomes simplified because large old trees disappear from the forest. The species composition shifts to tree species that are favoured by the respective harvesting strategy. The overall ecological impact increases linearly with the amount of extracted wood. Simulation results allow to define management strategies that balance conservation and production objectives, promote the regeneration of desired tree species, or minimise shifts in the species composition of the forest. Process-based forest models enhance our understanding of the dynamics of species-rich moist forests and are indispensable tools to assess long-term implications of anthropogenic disturbances on forest ecosystems. Thereby they contribute to the conservation and sustainable use of native forests outside protected areas. Contents 1 Introduction . 1 VII 1.1 Relevance . 1 1.2 Aims . 2 1.3 Approach . 3 1.4 Structure of the thesis . 4 1.5 References . 5 2 The study areas . 7 2.1 Tropical montane cloud forest in central Veracruz, Mexico . 7 2.1.1 Introduction to tropical montane cloud forests . 7 2.1.2 Abiotic conditions and forest characteristics . 9 2.1.3 Land use . 11 2.2 Valdivian temperate rain forest in northern Chiloé Island, Chile . 12 2.2.1 Introduction to temperate rain forests in southern South America . 12 2.2.2 Abiotic conditions and forest characteristics . 13 2.2.3 Land use . 15 2.3 References . 17 3 The process-based forest growth model FORMIND2.3 . 21 3.1 General description . 21 3.1.1 Purpose . 21 3.1.2 State variables and scales . 21 3.1.3 Process overview and scheduling . 22 3.1.4 Design concepts . 22 3.1.5 Initialisation . 23 3.1.6 Input . 23 3.2 Adaptations of FORMIND2.3 . 24 3.2.1 Recruitment . 24 3.2.2 Growth . 24 3.2.3 Geometry . 25 3.2.4 Logging . 25 3.2.5 Natural disturbances . 25 3.3 References . 25 VIII 4 Dynamics of tropical montane cloud forest in central Veracruz, Mexico . 27 4.1 Introduction . 28 4.2 Methods . 29 4.2.1 Study sites . 29 4.2.2 Model description . 29 4.2.3 Model parameters . 30 4.2.4 Simulations . 34 4.3 Results . 34 4.3.1 Comparison of model predictions with field observations . 34 4.3.2 Simulation of forest regeneration after disturbance . 37 4.4 Discussion . 38 4.4.1 Model parameters . 38 4.4.2 Verification of model results . 38 4.4.3 Forest regeneration . 39 4.5 Conclusions . 39 4.6 References . 39 5 Ecological impacts of fuelwood extraction on tropical montane cloud forest in central Veracruz, Mexico . 43 5.1 Introduction . 44 5.2 Methods . 46 5.2.1 Study sites . 46 5.2.2 The process-based forest growth model FORMIND . 47 5.2.3 Model evaluation . 48 5.2.4 Selective logging of old-growth forest . 49 5.2.5 Assessment of logging scenarios . 50 5.3 Results . 51 5.3.1 Tree biomass . 51 5.3.2 Example simulations . 52 5.3.3 Total yield . 53 5.3.4 Forest structure and composition . 54 5.4 Discussion . 58 5.4.1 Implications of “tala hormiga” for forest structure and composition . 58 5.4.2 Recommendations for sustainable fuelwood extraction . 60 5.5 Conclusions . 62 5.6 References . 62 6 Secondary tropical montane cloud forests: potential for provision of IX ecosystem services and fuelwood . 67 6.1 Introduction . ..