Towards effective reforestation: growth and commercial value of four commonly planted tropical timber species on infertile soils in Panama

Finding suitable tree species that not only grow well on nutrient poor soils but are also safe financial investments is one of the major obstacles to successful reforestation efforts in the tropics. Our study compared the financial viability and growth of valuable timber species in monocultures and mixtures on infertile soils. Our work shows the extraordinary growth in volume and value of Dalbergia retusa and Terminalia amazonia while underscoring the poor financial viability of Tectona grandis and Pachira quinata, all commonly planted timber species in Panama and much of Central and South America. Using Bayesian statistics, our predictions show that T. amazonia monocultures could reach nearly 200 m(3) ha(-1) of merchantable volume after 30 years compared to the similar to 40 m(3) ha(-1) that T. grandis could accumulate in the same time frame. While D. retusa monocultures did not have the highest predicted merchantable volumes of all the species, it did have the highest predicted net present value (NPV), with a predicted mean NPV of >US$97,000 ha(-1), quadrupling the species with the next highest monoculture's NPV, T. amazonia monocultures (similar to US$20,000 ha(-1)). Our work emphasizes that reforestation can be financially viable on low nutrient soils, even in the absence of fertilization or other silvicultural manipulations, if species selection and site are carefully considered and matched.

Automated summary

Finding suitable tree species for reforestation efforts in the tropics on nutrient poor soils that are also financially viable is a major obstacle. This study compared the financial viability and growth of valuable timber species in monocultures and mixtures on infertile soils. The results showed the extraordinary growth of Dalbergia retusa and Terminalia amazonia, highlighting the poor financial viability of Tectona grandis and Pachira quinata. The study emphasizes the importance of careful species selection and site matching for successful and financially viable reforestation on low nutrient soils.