Impacts of Herbicide Application and Mechanical Cleanings on Growth and Mortality of Two Timber Species inSaccharum spontaneumGrasslands of the Panama Canal Watershed

Abstract

AbstractReforestation has been suggested as a strategy to controlSaccharum spontaneum, an invasive grass that impedes regeneration in disturbed areas of the Panama Canal Watershed (PCW). In this study, the effects of different intensities of herbicide application and mechanical cleanings on the growth and mortality ofTerminalia amazoniaandTectona grandissaplings were evaluated inS. spontaneumgrasslands within the PCW. Both species exhibited greater height, basal diameter, wood volume index, wider crown diameters, deeper live crowns, and lower mortality with increasing intensity of mechanical cleanings and herbicide application. Height and competition ofS. spontaneumcorrelated negatively with intensity of mechanical cleanings and herbicide application. Grass control costs did not differ between tree species but did increase significantly with intensity of mechanical cleanings and herbicide application. We recommend fire suppression, annual herbicide application, and at least four mechanical cleanings per year inTec. grandisplantations during the first 3 years of plantation establishment. Given the slower initial growth and mortality patterns ofTer. amazonia, aggressive grass control treatments should be continued until individuals are sufficiently large to effectively shadeS. spontaneum. Results from this study suggest that reforestation with commercial timber species can rapidly establish and controlS. spontaneumgrowth in the PCW. Reforestation of areas already invaded or at risk of being invaded byS. spontaneumappears to be a viable strategy to reduce its abundance and subsequent negative ecological effects in the PCW.