Species mixture effects in northern red oak-eastern white pine stands in Maine, USA

摘要: Growth and yield studies of mixed-species stands lack generality, though mixture effects appear to be most likely in species with contrasting traits and/or vertical stratification. The northern red oak (Quercus rubra L.) – eastern white pine (Pinus strobus forest type the US Northeast is dominated by intermediate shade tolerance, often a spatially heterogeneous lower canopy shade-tolerant maple (Acer rubrum hemlock (Tsuga canadensis (L.) Carr.). We examined neighborhood scale plots (0.02 ha) variable mixtures these range age structure (44–140 years mean age) southern Maine. Linear mixed regression was used model surface area, stem biomass growth, across gradients composition. With stocking, age, site quality held constant, more species-diverse had denser canopies faster but than compositionally simpler plots. For variety structures, produced area growth would expected if interspecific competition were equal intraspecific, on one or other. Lower contributed higher plot-level values all variables plots, there no evidence suggest that any stocking without displacing other some degree. This study demonstrates oak, along species, can grow fine-scale even- two-aged structures sacrificing productivity, conditions enhancing it.