Carbon isotopes in Sphagnum from Kyushu, Japan, and their relationship with local climate

δ¹³C was measured in two species of Sphagnum moss (Sphagnum palustre and Sphagnum fimbriatum), collected from the Genseinuma-fen in Unzen, Northern Kyushu in March, 2010. From examination of several specimens of the two species near the sampling site, the growth rates were determined to be sufficiently high to allow interpretation of annual δ¹³C variation through comparison with locally recorded climatic information. The d13C values of different organs (stems and branches) and components (bulk and cellulose) exhibit consistent variations, although the differences between them appear to be species-specific. Both species, but in particular S. palustre, exhibited smooth increases in δ¹³C towards the central part of the sample length (total 16-17 cm), corresponding to approximately half a year's of growth. Temperature is considered to be the primary factor affecting the δ¹³C values of both species, with the observed δ¹³C maximum corresponding to the summer of the previous year. However, the positions of the peaks in branches and stems differed by 2 or 3 cm, reflecting the fact that stem growth was preceded by branch growth. Considering the relationship between δ¹³C and temperature, a rise of 1% in δ¹³C is seen to correspond to a rise of 14°C and 10°C for S. palustre and S. fimbriatum, respectively.