Abstract
Firewood pieces and kiln materials recovered from the Kouyasu kiln group in Takahata-Town, Yamagata, were identified, and their diameters and annual-ring widths were restored in five su-e kilns of the late 7th to the incipient 8th centuries and a charcoal kiln of the late 9th to the early 10th centuries. The oldest kiln C1 used Carpinus sect. Eucarpinus and Acer, whereas newer kilns B1 and B2 mainly used Pinus subgen. Diploxylon. This difference apparently showed an increase of Pinus subgen. Diploxylon due to kiln activity, but its firewood pieces had more annual rings, being derived from older growth than those of Carpinus sect. Eucarpinus or Acer. Thus, the Kouyasu kiln group first used thin broadleaved trees less than 10 cm in diameter, but, when they were consumed, used Pinus subgen. Diploxylon trees over 10 cm in diameter. The newest kiln B2 was operated when firewood was scarce, leading to the end of this kiln group. The charcoal kiln used only Quercus sect. Prinus from the surrounding forest with even diameters and numbers of growth rings, indicating a standard in charcoal products. The vegetation must have recovered during the 200 years since the termination of su-e kilns to allow charcoal production.
