ABSTRACT
Boreal forest and Arctic tundra, the principal ecosystems of northern North America, have become a focal point of scientific, economic, and Native concerns respect to the potential impacts of a warmer climate. Approximately 13 percent of the Earth’s carbon is in the cold, permafrost-dominated soils of the boreal forest, and an additional 14 percent is sequestered in the cold soils of the tundra. Low soil temperature, low pH, low nutrient content, and anaerobic conditions in organic soils contribute to slow decomposition and accumulation of large quantities of carbon. In recent geological history, northern latitude ecosystems have been a major sink for atmospheric carbon, much of it accumulated in the past 10,000-year postglacial period. The boreal forest-tundra ecotone is distinguished by tree line, the northern-most limit of tree distribution, which coincides with the July 13°C isotherm, roughly the southern extent of the Arctic front during the summer.
