Dynamics of a broadleaved ( Castanea sativa) conifer ( Pseudotsuga menziesii) mixed stands in Northern Portugal

Abstract

In nature, forest ecosystems are composed by mixtures of species located in the understorey, intermediate and overstorey layers and a potential increase in productivity with mixed stands and plantations, compared to pure stands of the component species is widely accepted, although this has not generally been incorporated into forestry practice. In this experimental planting study, the types of mixtures tested includes three row mixtures with species changing in the planting line, two line mixtures with species changing between the planting line and two monocultures. The species growth pattern was analysed and productivity comparisons between mixed stands and pure stands of the component species were made using the relative yield (RY) and relative yield total (RYT) concepts. The species shows different top height growth patterns which are not influenced by the mixtures tested. Castanea sativa responds well to competitive pressure from Pseudotsuga menziesii which shows a higher productivity. In the row mixtures, the positive effect of interspecific competition yields to RYT values greater than 1.0. Mixture RYT values are steadily increasing with time and C. sativa monoculture has been the most attractive economic solution, although its importance compared with the most productive mixtures is diminishing over time. This species mixture represents a flexible silvicultural system, which will be in the future, a very important land use alternative in mountain areas.