A method for forest site quality assessment was developed for use in tropical areas. It established a statistical relation between site synecological coordinate scores, as environmental quantifiers, and site physiognomic characteristics. This relation can be used to predict species with good potential growth for a given site. The method was tested with data from Costa Rica, and results indicate that the method could be of practical use for foresters in Costa Rica and other tropical countries.;To develop the method, basic theoretical considerations were made. I proposed that new units of ecological research, stratification by climate and soil, provide a more reasonable framework for communication and utilization of research results among ecologists. Also, this type of unit provides an easy way of mapping vegetation trends. Within this basic unit of research, the method of synecological coordinates (MSC) was used to develop environmental quantifiers.;Theoretical considerations were stated in light of current practices in ecological studies, and a comparison of the MSC with three ordination techniques was performed. Results showed that the MSC provided an easier way to classify sampling units and plant species in the ecosystem space.;A computer program, SYCOOR, was developed to facilitate the use of the MSC.