Evaluación de la productividad de sitios multiespecíficos a través de funciones de distancia

A methodology to estimate relative productivity in forest sites with several species throughout an efficiency index derived from radial and directional distance functions is described. The paper introduces the distance function as a measure of relative efficiency in the use of resources by mixed populations. The estimation procedure is described either when several inputs and outputs are included as well as when the estimates are based on one or several products (species). A methodology to isolate the effect of density to estimate total volume productivity is also introduced and used to compare different estimates of site quality including the traditional site index. Results show that estimation of productivity in multi species sites depends on the site composition since sites become more efficient as they are composed by more species. They also show that the traditional site index estimate is not a good estimate of total site productivity in multi species sites and that the best estimates of efficiency under these conditions, in terms of their relationship with actual productivity are those derived from radial distance functions when all species are incorporated in the estimation. Some deficiencies of the procedure are also discussed as well as some directions to future research on the topic.