ABSTRACT
Recently in Japan, bark enclosed in tree trunks, known as tree “bark pock ets,” has been shown to provide some of the most readily available historical specimens for monitoring air pollution (1). Bark pockets are common in tree trunks. The phenomenon is well recognized by forestry technicians, saw millers, and dendrologists because trunks with bark pockets often have problems with lack of strength, discoloration, and microbial decomposition of the xylem layer. Bark pockets have not previously been identified as being useful parts of a tree. Their potential value for scientific research has previously been overlooked. Har vested trunks with bark pockets have mostly been discarded as waste. Therefore, many forest trees identified as containing bark pockets have been left standing and not harvested.
