This study examines how much mosses contribute to the ecosystem by storing carbon in their plant bodies (biomass). They found that the mosses contributed 25% of the gross primary productivity (above and below ground growth) in the arctic ecosystem that they examined. This is a significant contribution to the ecosystem carbon cycle! Hence one of the authors' final conclusions is that mosses need to be included in vegetation carbon models in order to have an accurate picture of the carbon cycling.
I think that this is a really important take-home message. Especially in far northern ecosystems, mosses make up a large portion of the plant life. If we are to understand and plan for the effects of global climate change on these far northern places, we cannot ignore the mosses.
Street LE, Subke JA, Sommerkorn M, Sloan V, Ducrotoy H, Phoenix GK, Williams M (2013). The role of mosses in carbon uptake and partitioning in arctic vegetation. The New phytologist PMID: 23614757
Sphagnum mosses (aka. peat mosses, pictured below) were one of the focal species of their study.