Abstract
At the Bibai peatlands in Hokkaido, Japan, the decomposition of peat is enhanced due to the drying tendency of the Peatland. Accordingly, the Sasa senanensis community invades the Sphagnum colmmunity, whose area is diminishing rapidly. Peat samples were collected from this area on a transect line which passed through the original Sphagnum community as well as that of the jnvading Sasa community. This paper aimed to clarify the effect of the change in vegetation as well as the decomposition of peat on the composition of fatty acids and sterols in peat. The total yield of fatty acid in the more decomposed (<2 mm) fraction was larger than that in the less decomposed (>2 mm) fraction. It was also remarkably larger at sites where the decomposition of peat was enhanced. The distribution of fatty acids in peat was bimodal, peaking at palmitic acid and at cerotic acid. Results of regression analysis and principal component analysis also suggests that fatty acids with chain lengths shorter than 18 and longer than 20 behave differentry. Among individual fatty acids, the yields of palmitic acid and arachidic acid were larger at sites covered densely with Sasa senanensis. Yield of stearic acid and cerotic acid, on the other hand, tended to be larger at sites where the vegetation of Sphanum was preserved. Yields of fatty acids with a chain Iength longer than 24 were remarkably higher at sites where the decomposition of peat was enhanced due to the lowering of the water table. As for sterols, β-sitosterol, campesterol, stigma-sterol and cholesterol were detected in peat samples. Sterols except cholesterol were considered to originate from plants, and more abundant in the >2 mm fraction than in the <2 mm fraction as well as at sites with denser Sasa senanensis vegetation than Sphagnum vegetation. Cholesterol, on the other hand, was considered to originate from the soil biota which decompose plant residues, and was contained in larger amounts in the <2 mm fraction than in the >2 mm fraction.
