Acknowledgements
This research was funded by the United Nations University (UNU), the Centro Agronomico Tropical de Investigacion y Ensefianza (CATIE), and the Empresa Celulosa de Turrialba. Field and office assistance was provided by Paulo Dittel, several UNU/CATIE fellows, Manuel Salazar and Mario Leiva. Bryan Finnegan and Danilo Pezo reviewed the manuscript