Root Growth, Respiration, and Carbon Dioxide Evolution in an Arctic Tundra Soil

Most of the living plant material of moist tundra in arctic Alaska is in the 0-to-10-cm layer of the cold soil, and above permafrost. This research measured root growth at low temperatures in plants of three dominant species of this tundra: a grass (Dupontia fischeri R.Br.) and two sedges (Carex aquatilis Wahlenb. and Eriophorum angustifolium Honck.). Respiration rates of roots and rhizomes were measured both in the field and under controlled conditions using an infrared gas analysis system. Two variations of measuring root respiration were used: excised new root segments and intact whole root systems. The latter method provided lower but probably more realistic rates. Under controlled conditions, root growth rates of the three species were similar. However, Eriophorum roots grew more rapidly than those of other species at temperatures just above 0°C. This was also noted in the field where roots of this species grew along the upper edge of the frozen soil. Roots of all species could be frozen for several days and resume normal growth within 12 h after thawing. The 0-to-10-cm layer of tundra soil at Barrow accounts for 80 to 90% of total soil carbon dioxide evolution. Rough estimates indicate that 50 to 90% of this soil carbon dioxide flux is derived from respiration of roots and rhizomes of vascular plants.