Reflected-light image analysis of conifer tree rings for reconstructing climate

We use reflected-light image analysis to measure brightness of conifer rings, and we use brightness as an alternative to density for reconstructing climate. Using densitometry and image analysis, we measured cores from red spruce (Picea rubens Sarg.) growing at Elephant Mountain, Maine, and then compared statistical characteristics of density and brightness and climate-tree growth models using density or brightness. Auto-correlational and cross-correlational statistics of density and brightness do not differ substantially, and late wood density and brightness both correlate with April-May average temperature, which both tree-ring variables reconstruct equally well. April-May temperature was highly variable during most of the nineteenth century and was below average during the AD 1830s, 1870s and late 1880s. When done carefully, reflected-light image analysis can substitute for X-ray densitometry for measuring tree rings to reconstruct climate of the latest Holocene.