Mission 2007 - Hydrocarbon Potential Evaluation Team

Basis of food chain and energy source

The mosses and lichens are less freely consumed by the herbivores in the whole arctic region than the other angiosperms. Reason for low consumption on mosses and lichens may be that they are not very digestible due to a high crude fibre content resulting in part from lignin-like phenolic compounds in the cell walls. Species that would feed on mosses include many arthropods with sucking mouthparts, such as mites, and also tardigrades, dipteran and lepidopteran larvae. It is also suspected that animals such as geese may benefit from arachidonic acid which is present in mosses. This highly unsaturated fatty acid could increase limb mobility at low temperature and protect cell membranes against cold.

Lichens are well known to be crucial for caribou and reindeer (Rangifer tarandus), and thus to indigenous human populations relying on these mammals. Graminoids, willow leaves and forbs are preferred by these animals in the summer, but lichens often represent some 60-70% of winter food. Generally, an adult reindeer requires up to 5kg dry weight of lichen daily in winter and grazing about 2000kg/m^-2 in six months. Lichens are rich in carbohydrate, are readily digested by caribou though not by other mammals for the reasons stated above, and form an effective and available energy source in winter when animals need intensive metabolism to generate body heat. Yet, they are deficient in protein, lipids and several essential mineral elements. How then do the animals cope with this? The animals smartly utilize fat reserves and break down muscle, with replenishment through feeding on nutritious young angiosperm leaves in spring.

Mosses form a minor part of the diet of several arctic rodents, and are more freely consumed by Lemmus spp.. In peak years, consumption by lemmings (L. sibericus) in Alaska may reach 25% of above-ground primary production, with mosses forming 5-20% of the diet in summer and 30-40% in winter. Though mosses are not readily disgestible by lemmings, they provide good source of unsaturated fatty acids and minerals such as calcium, magnesium and iron.