Moss production in a black spruce Picea mariana forest with permafrost near Fairbanks, Alaska, as compared with two permafrost-free stands

investigated. Overall annual moss production at the intensive black spruce site was about 120 g m-1 yr-1 or about twice as high as the corresponding annual spruce production. Maximum rates of net photosynthesis varied from 2.7 mg CO2 g-1 h-' in Polytrichum commune Hedw. to 0.6 mg CO2 g-1 h-1 in Sphagnum nemoreum Scop. The photosynthesis of overwintered leaves early in the season was low and as a result of new growth a steady increase in net photosynthesis occurred throughout the season. Leaf water content was found to be the most important limiting factor for growth under natural conditions. There was a strong increase in growth and photosynthesis of Sphagnum nemoreum