Influencia de las especies del dosel en la disponibilidad de recursos y regeneración avanzada en un bosque templado lluvioso del sur de Chile

Understory habitat heterogeneity is believed to be a factor promoting maintenance of species diversity in forest communities. The influence of over storey species identity on resource availability and variation in composition of advanced regeneration was studied in a temperate rain forest in southern Chile. The forest overstorey was dominated by the broadleaved evergreens Laureliopsis philippiana, Aextoxicon punctatum, Eucryphia cordifolia and Nothofagus dombeyi. Availabilities of diffuse light, nitrogen, phosphorous and calcium were measured under these four over storey species, as was nutrient content of leaf litter. Advanced regeneration was sampled in plots beneath each over storey species, and results analyzed by ordination. There were significant differences in light transmission, nutritional content of leaf litter and availability of N-NO₃ and P beneath the four species. Nevertheless, all nutrients showed low availability due to low mineralization and high immobilization. Ordination results indicate that the composition of advanced regeneration under N. dombeyi and L. philippiana differed from the composition of regeneration under A. punctatum or E. cordifolia. The ordination suggested that light level explained a large proportion of compositional variation. We propose that species regenerating in the understory differed more in shade tolerance than in nutritional requirements, light being the most limiting resource in the understorey.