Native trees can improve ecological function and increase economic value of exotic plantations: Lessons learned from the Panama Canal Watershed
Presentation Type
Oral Presentation
Abstract/Artist Statement
It is well known that tropical forests are being deforested and degraded at accelerated rates to provide food, fiber, and other materials. After clearing, the once highly-productive and biodiverse forests are converted to other non-forest land uses, such as human settlements and cattle grazing. Plantation forestry is thought to offer an ecological-economic “win-win” by providing lumber and income to local communities, while at the same time preserving some of the primary ecological benefits of forests, like wildlife habitat and regulating water. However, if plantations of exotic species grow poorly and fail to deliver economic benefits, then landowners have less incentive to continue growing trees.
For example, in the Panama Canal Watershed (PCW), a high-priority conservation area for wildlife connectivity and for maintaining year-round water supply for the Canal, large areas have been converted to plantations of teak (Tectonia grandis), a high-value, exotic timber species. However, poor teak performance and low economic returns on plantations are major factors limiting the upkeep of existing plantations and the establishment of new ones, and in some cases, land-owners are transitioning plantations to cattle ranching despite decades of government- and NGO-led reforestation programs and subsidies.
One strategy for improving the ecological and economic benefits of timber plantations is through enrichment plantings, or the establishment of target species under an existing canopy (in this case, underperforming teak trees). Although past studies have identified promising, high-value native species which may benefit from the partially-shaded establishment conditions of an enrichment planting, there is limited information on how native species perform across a range of microsite conditions and their responses to management practices such as fertilization.
To address this gap, researchers with the Smithsonian Tropical Research Institute have been studying the effectiveness of planting 6 high-value native trees (Byrsonima crassifolia, Dalbergia retusa, Dipteryx oleifera, Hieronyma alchorneoides, Platymiscium pinnatum, and Terminalia amazonia) in the understory of teak plantations. As part of this project, I designed a study to test the environmental factors that influence growth of these native species, in order to assist with the development of appropriate planting guidelines. Specifically, I am interested in the effects of light availability, crowding from teak, microsite productivity and fertilizer inputs on the growth and mortality of study tree species. My initial results suggest that teak plantations can provide a suitable environment for establishment and early growth, but indicate differences among native species which may be related to shade tolerance and associations with below-ground microbial symbionts.
This presentation will provide a brief background on reforestation efforts and timber plantations in the PCW, and discuss preliminary results of the enrichment planting field trial. The management implications of these initial findings will be explored, as well as potential relevance to broader ecological questions surrounding how species functional traits and microbial associations may shape competitive outcomes for abiotic resources, and how/if physiological characteristics predict responses to fertilizer and light.
Mentor Name
Cara Nelson
Native trees can improve ecological function and increase economic value of exotic plantations: Lessons learned from the Panama Canal Watershed
UC 332
It is well known that tropical forests are being deforested and degraded at accelerated rates to provide food, fiber, and other materials. After clearing, the once highly-productive and biodiverse forests are converted to other non-forest land uses, such as human settlements and cattle grazing. Plantation forestry is thought to offer an ecological-economic “win-win” by providing lumber and income to local communities, while at the same time preserving some of the primary ecological benefits of forests, like wildlife habitat and regulating water. However, if plantations of exotic species grow poorly and fail to deliver economic benefits, then landowners have less incentive to continue growing trees.
For example, in the Panama Canal Watershed (PCW), a high-priority conservation area for wildlife connectivity and for maintaining year-round water supply for the Canal, large areas have been converted to plantations of teak (Tectonia grandis), a high-value, exotic timber species. However, poor teak performance and low economic returns on plantations are major factors limiting the upkeep of existing plantations and the establishment of new ones, and in some cases, land-owners are transitioning plantations to cattle ranching despite decades of government- and NGO-led reforestation programs and subsidies.
One strategy for improving the ecological and economic benefits of timber plantations is through enrichment plantings, or the establishment of target species under an existing canopy (in this case, underperforming teak trees). Although past studies have identified promising, high-value native species which may benefit from the partially-shaded establishment conditions of an enrichment planting, there is limited information on how native species perform across a range of microsite conditions and their responses to management practices such as fertilization.
To address this gap, researchers with the Smithsonian Tropical Research Institute have been studying the effectiveness of planting 6 high-value native trees (Byrsonima crassifolia, Dalbergia retusa, Dipteryx oleifera, Hieronyma alchorneoides, Platymiscium pinnatum, and Terminalia amazonia) in the understory of teak plantations. As part of this project, I designed a study to test the environmental factors that influence growth of these native species, in order to assist with the development of appropriate planting guidelines. Specifically, I am interested in the effects of light availability, crowding from teak, microsite productivity and fertilizer inputs on the growth and mortality of study tree species. My initial results suggest that teak plantations can provide a suitable environment for establishment and early growth, but indicate differences among native species which may be related to shade tolerance and associations with below-ground microbial symbionts.
This presentation will provide a brief background on reforestation efforts and timber plantations in the PCW, and discuss preliminary results of the enrichment planting field trial. The management implications of these initial findings will be explored, as well as potential relevance to broader ecological questions surrounding how species functional traits and microbial associations may shape competitive outcomes for abiotic resources, and how/if physiological characteristics predict responses to fertilizer and light.