THE THERMAL STATE OF SOILS NORTHERN YAKUTIA
D.G. Fedorov-Davydov1, S.P. Davydov2, A.I. Davydova2, D.G. Shmelev1, V.E. Ostroumov1, A.L. Kholodov1, V.A. Sorokovikov1
1 Institute of Physicochemical and Biological Problems in Soil Science, RAS, 2, Institutskaya str., Pushchino, Moscow region, 142290, Russia; muss-96@yandex.ru
2 North-Eastern Science Station, Pacific Ocean Geography Institute, FEB RAS, P/O box 18, Cherskiy Community, Nizhnekolymskiy Region, Yakutia, 678830, Russia; davydoffs@mail.ru
Soil profile temperatures in Northern Yakutia depend on their location in tundra or taiga zones and subzones, water content (drainage conditions), ice content in the underlying permafrost, vegetation cover, as well as soil particle size (texture) and thickness of organic horizons. The studied soils differ mainly in winter temperatures. The mean coldest month temperatures of loamic soils measured at 20 cm below the surface are 10 °C higher in northern taiga than in southern tundra. However, the mean annual temperatures at this depth vary from –4.3 to –9.7 °C in tundra and from –1.2 to –4.9 °C in taiga. This discrepancy is primarily due to the effect of the snow cover which is thicker, less dense, and more stable in the forest landscapes. Sandy podbur soils (spodic turbic cryosol) have larger thawing degree-day sums and deeper 0 °C, 5 °C, and 10 °C isotherms than the zonal loamic soils. Xeromorphic soils of steppe landscapes in the northern taiga subzone have the warmest summer temperatures and are most responsive to temperature change.
Northern Yakutia, tundra soils, northern taiga soils, soil cover heterogeneity, temperature regime of soil, active layer, seasonal thaw