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Sugar maple is among the most important commercial tree species in the northern United States. Sawlogs with the highest proportion of white wood to discolored heart are the most valuable; logs with more than one-half the log diameter in dark wood must be marketed as pallet logs. Foresters, loggers, and landowners have long speculated about regional variations in heart size, but to date, no one has tested these theories. We examined 53 harvest sites across six northern states and found no significant variation in heart size related to geography, ecoregions, or soil orders. We did observe larger hearts on sites on Spodosols than on Alfisols, which are more base rich. Heart size increased only slightly with diameter at most sites, such that the heart-size ratio decreased (P < 0.001 ), suggesting that the risk of finding large hearts does not increase with tree age, as previously believed. [ABSTRACT FROM AUTHOR]