COMPARATIVE-STUDY OF THE MASS-LOSS RATE OF MOSS LITTER IN BOREAL AND SUB-ALPINE FORESTS IN RELATION TO TEMPERATURE

The moss Hylocomium splendens shows a very wide distribution in the No rthern Hemisphere and may be useful as an indicator of climatic change on a global scale. We aimed to establish a convenient method to estim ate the annual rate of litter mass loss of this species. The rate was calculated from the annual litter production rate and the amount of li tter accumulated in the field. The litter production rate was estimate d by analysis of the moss shoot growth. The rates calculated by this m ethod tended to be larger than estimates obtained by the litter bag me thod. Using this method, we examined the difference in the litter mass loss rate along the altitudinal and latitudinal temperature gradients . The moss samples were collected from three boreal forests in Canada and four subalpine forests in Japan. At the subalpine sites, the annua l rate of litter mass loss was within the range of 10-24% and tended t o be smaller with increasing altitude. The rates in the boreal sites w ere similar to those in the subalpine sites despite lower mean annual temperatures. A significant log-linear relationship was observed betwe en the annual mass loss rate and the cumulative value of monthly mean air temperatures higher than 0 degrees C (CMT). Nitrogen concentration of the litter was positively correlated with mean annual air temperat ure. Site to site variation in the annual mass loss rate was largely e xplained by CMT and nitrogen concentration of the litter.