Patterns of translocation of carbon in four common moss species in a black spruce (Piceamariana) dominated forest in interior Alaska

Abstract

The patterns of translocation of carbon in different-age tissues of four common moss species in a black spruce (Piceamariana (Mill.) B.S.P.) dominated forest near Fairbanks, Alaska, were studied by 14C labelling and carbohydrate analysis. A simple, in-vial combustion technique was developed for combustion of small (< 10 mg) radioactively labelled samples of plant tissue. The method was used to measure specific activity of 14C in moss tissue 2 h and 5, 15, and 25 days after labelling with 14CO2 gas in sealed chambers. The procedure was repeated three times during the summer. Patterns of 14C translocation varied by species; Polytrichumcommune Hedw. retained the most label after 2 h and Sphagnumsubsecundum Nees. the least. Polytrichumcommune had the second-highest fraction of 14C in brown tissue after 35 days and S. subsecundum the highest. Hylocomiumsplendens (Hedw.) B.S.G. and Pleuroziumschreberi (Brid.) Mitt, did not show consistent patterns of translocation 2 h or 35 days after labelling. 14C was found to accumulate in the growing shoot tips and in the brown tissue of all four species. Loss of 14C because of respiration was high in all four species during the first labelling period indicating high rates of photosynthesis and growth during the peak summer season. The carbohydrate analysis indicated that the increase in 14C activity in brown tissue by the end of the season was due to translocation for storage. In all species there was a strong increase in the storage polysaccharide content by the end of the season after the growth was finished, especially in brown tissue.