Maps depicting the within-tree wood property variation of some North American conifers: a review

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Knowledge of wood property variation within trees is critical for understanding age effects on wood formation and for improved utilization of forests, and maps provide an effective way to efficiently summarize and visually represent variability. Despite the importance of maps, examples for North American conifers are rare. Most studies focus on plantation grown trees, with the majority examining loblolly and radiata pine. For these species almost all maps can be categorized into two groups related to tracheid differentiation processes. One group includes properties related to secondary cell wall formation, e.g., density, and the second relates to tracheid enlargement, e.g., tracheid length. Maps for trees from natural forests are largely limited to density and are highly variable indicating site effects are large. The degree of variation within a species made it impossible to develop conclusions regarding general patterns of variation as with plantation grown trees. The identified density maps are consistent with the three radial variation patterns defined by Panshin and de Zeeuw (1980) (Type 1 (increase), 2 (decrease then increase), and 3 (decrease)). A focused research effort to better visualize wood property variation is required, particularly for species demonstrating Type 2 and 3 radial density patterns.