Download Population-level impact of density-dependent seedling mortality on

Chris Free
April 16th 2010
Research Symposium
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Valuable timber species
 Workable, durable, beautiful
 Decorative woodwork, furniture, etc
 Single tree - $20,000, $1800 m-3
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Vulnerable to exploitation
 Natural range – rapid anthropogenic land conversion
 Life history - low density, secondary colonizer,
disturbance dependent seedling regeneration
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Deforestation over 63% of mahoganies range
Selective logging of 85-90% remaining adults
Grogan et al. 2009
Grogan et al. 2009
Grogan et al. 2009
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CITES Appendix II - demonstration of
sustainable harvest by exporting country
Little empirical basis for evaluating
sustainability of proposed regulations
Inclusion in Appendix II of the neotropical populations of Swietenia
macrophylla King, (Meliaceae), including logs, sawn timber, veneer
and plywood, in accordance with Article II, Paragraph 2A, of the
Convention and Resolution Conference 9.24, Annex 2A. The
objective of this listing is to promote sustainable management
of S. macrophylla in order to help ensure its further
conservation and trade (CITES 2002).
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Verwer et al. (2009), Grogan et al. (2009), Grogan
and Landis (in prep) – spatially implicit matrix
based and individual based modeling strategies
 No density-dependence - requires spatially explicit
approach
Grogan and Landis (in prep)
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Population size/density modifies population
vital rates (recruitment, growth, mortality)
 Competition, predation, pathogens, disease
 Janzen-Connell Model: distant and/or density
responsive enemies cause increased mortality of
progeny near parent forcing spacing of conspecifics
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Distant- and density-dependent interactions
observed in big-leaf mahogany populations
 Leaf herbivory by specialist moth caterpillar
▪ Increased defoliation and seed predation
▪ Decreased growth and recruitment success
Norghauer et al. 2006a
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The purpose of my project is to examine the
population-level consequences of densitydependence on big-leaf mahogany
 Develop a more robust population growth model
 Assess applicability of Janzen-Connell predictions
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A spatially explicit model developed using
NetLogo language and interface
Parameterized using the field data of Grogan
and Landis (in prep) and Norghauer (2006a,b)
 204 ha 100% inventoried field site in Pará, Brazil
 Experimental exclosures in Pará, Brazil
 Disturbance, growth, mortality, reproduction
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Convention on International Trade in Endangered Species (CITES). 2002.
Consideration Of Proposals For Amendment Of Appendix I And II: Swietenia
macrophylla. Prop.12.50. [http://www.cites.org/eng/cop/12/prop/index.shtml
accessed 14 March 2010].
Grogan, J., and Landis, R.M. 2010. Mahogany population dynamics in Brazil and
implications for international trade. Forthcoming.
Grogan, J., Blundell, A.G., Landis, R.M., Youatt, A., Gullison, R.E., Martinez, M.,
Kometter, R., Lentini, M., and Rice, R.E. 2009. Over-harvesting driven by
consumer demand leads to population decline: big-leaf mahogany in South
America. Conservation Letters 3: 12-20.
Norghauer, J.M., Malcolm, J.R., and Zimmerman, B.L. 2006. Juvenile mortality
and attacks by a specialist herbivore increase with conspecific adult basal area of
Amazonian Swietenia macrophylla (Meliaceae). Journal of Tropical Ecology 22:
451-460.
Verwer, C., Peña-Claros, M., van der Staak, D., Ohlson-Kiehn, K., and Sterck,
F.J. 2008. Silviculture enhances the recovery of overexploited mahogany
Swietenia macrophylla. Journal of Applied Ecology 45: 1770-1779.