Document Type

Article

Publication Title

Maine Woodlands

Publisher

Maine Woodland Owners

Publication Date

Summer 6-2023

Issue Number

6

Volume Number

48

Abstract/ Summary

Tree rings, formed annually in temperate forests by the vascular cambium tissue, are composed of xylem and are crucial for water conduction and structural support. This wood formation follows a predictable seasonal pattern, commencing in May and concluding in September. Initially, earlywood forms with larger tubes and thinner cell walls; subsequently, latewood develops with smaller lumina and thicker cell walls, creating the distinct annual rings. Wood types vary, with conifers having tracheid cells with small lumina, while hardwoods possess larger vessels and are categorized as either ring-porous (e.g., oak, ash) or diffuse-porous (e.g., maple, birch). Crucially, the true measure of wood growth is the total area added around the circumference, not merely the width of an annual ring. This understanding underpins dendrochronology, the use of annual variations in tree ring widths to reconstruct past climate and natural disturbances, such as forest fires or insect defoliation. For example, studies comparing red spruce and northern white-cedar have identified five distinct spruce budworm outbreaks between 1700 and 2000. Dendro-archaeology extends this to historical timbers, providing invaluable insights into forest history from periods long extinct in living trees, as demonstrated by salvaged timbers from the 1865 Dakins Building, which revealed spruce budworm outbreaks from 1709, 1762, and 1808. Silvicultural treatments can also be applied to increase wood production by expanding the tree’s crown and photosynthesis.

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