Forest regeneration under Tectona grandis and Terminalia amazonia plantation stands managed for biodiversity conservation in western Panama
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Plantations of Tectona grandis in Central America are widely perceived to suppress forest regeneration in their understories, yet few studies have tested this assumption. We surveyed the understory woody vegetation growing in 7-year-old stands of T. grandis and the native tree species Terminalia amazonia in a plantation in western Panama that was managed with both commercial timber and biodiversity conservation objectives. We predicted that if T. grandis suppressed forest regeneration then the understories of T. grandis stands would have a lower density of woody stems, smaller stems, and fewer species than stands of T. amazonia. None of our predictions were supported. Densities of woody stems were 0.56 ± 0.21 m−2 (mean ± SE) and 0.64 ± 0.10 m−2 in T. grandis and T. amazonia understories, respectively. Stem height structure was similar under both species, where stems <1 m height dominated. Understory species richness did not differ between the two species; in total, 27 and 30 woody species were sampled in T. grandis and T. amazonia stands, respectively. However, understory species composition differed between the two crop species. Overall, our results are inconsistent with the idea that T. grandis plantations suppress forest regeneration and suggest that the lack of woody vegetation in other T. grandis plantation understories may be attributable to management actions, such as understory thinning, rather than species effects of T. grandis. Further research is needed to compare T. grandis and native species for their effects on forest regeneration.
KeywordsDiversity Native species Reforestation Restoration
We thank Iliana Armién and Andreas Eke for facilitating research at the Futuro Forestal plantations, Emilio Mariscal for training, Carolina Sarmiento for help in making Fig. 1, and two anonymous reviewers for helpful comments on the manuscript. This research was undertaken as part of PRORENA, a collaborative native species reforestation research project between the School of Forestry and Environmental Studies of Yale University and the Center for Tropical Forest Science at the Smithsonian Tropical Research Institute. Financial support for PRORENA has been provided by the Frank Levinson Donor-Advised Fund at the Peninsula Community Foundation, the Levinson Family Foundation, and the Grantham Family Foundation.
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