Traditional ecological knowledge determined tree species choice in the construction of traditional folk houses in a snowy rural landscape in central Japan

Abstract

To elucidate the selection of tree species for timber in traditional folk house construction, I examined the species used in seven houses in four rural villages in central Honshu, Japan, a region subject to heavy snowfall. All houses were mainly constructed of beech (Fagus crenata), cedar (Cryptomeria japonica), and oak (Quercus crispula and/or Quercus serrata). The species composition was similar to that of the current surrounding woodlands, suggesting that these species grew in the region when the houses were built, although the vegetation structure changed in the interim. Beech, cedar, and oak trees grow and maintain their upright structure even in environments that experience heavy snowfall; therefore, these species may have appeared to be the best choices for construction timber in this region. Beech was mainly used for its bending strength, in slanting or horizontal structural elements; cedar in elements used as structural reinforcement; and oak in various elements, complementing the selection of beech or cedar. Important structural beams are typically made of beech timber. Its high bending strength was considered to reflect the nature of living beech trees, which form dominant stands in regions with heavy snow in Japan, due to their sturdiness and ability to stand upright under heavy snow loads. Although beech timber is currently considered to be unsuitable for construction due to its trait such as easy to twist or easy to rot, the results of this study suggest that selecting beech timber for structural elements that bear heavy snow loads was feasible for indigenous builders when the traditional houses were constructed. Consequently, beech-dominated forests may have influenced the architectural style of houses with large-beamed structures and may have been a factor contributing to the settlement of this region. Understanding traditional ecological knowledge may contribute to the promotion of sustainable wood resource use in the future.