Reindeer in tundra ecosystems: the challenges of understanding system complexity

The resilience of tundra ecosystems is limited, with relatively few key biotic components determining the general pattern of the dynamics of these systems. Sustainable use of reindeer pastures, which are natural tundra ecosystems, should take into account interactions within the whole complex of key components. Among the most important are the small herbivorous rodents. For example, during peak densities lemmings may reduce above-ground plant biomass by 50-70%. At the same time, rapid turnover of nutrients in the form of significant amounts of potassium, phosphorus and nitrogen that lemmings excrete in urine promotes vascular plant growth. It is concluded that these kinds of studies are essential for the sustainable management of Russia's grazing lands: 1) comparative studies of productivity, biological diversity and structure of plant communities under the different pressures exerted by the main groups of herbivorous animals (reindeer and small rodents), as well as under varying levels of industrial development; 2) studies of the direct and indirect effects of herbivorous mammals on biological turnover and energy flow within the system; 3) studies of the role of industrial contamination on the turnover of nutrients in tundra ecosystems.