Relationships between permafrost distribution and surface organic layers near Esso, Central Kamchatka, Russian Far East

Unique boreal forest, consisting mainly of sparse larch (Larix cajanderii), creeping pine (Pinus pumila) and birch forest (Betula ermanii), occurs above the lower elevational limit of discontinuous permafrost of about 500 m above sea level in the area around Esso, central Kamchatka (∼56°N). Permafrost is present beneath surfaces covered by Sphagnum or creeping pine, but is absent beneath birch forest. Thermal conductivities in mid-September are low in Sphagnum (0.07-0.19 W/(m·K)) and in the thick (13-20 cm) litter layer beneath creeping pine-covered areas (0.06-0.09 W/(m·K)). Seasonal changes in the subsurface ground temperatures beneath creeping pine show that the surface litter prevents ground temperature increases at depth in summer, resulting in a thin active layer (several decimetres). The surface organic layer appears to be the most important factor controlling the presence or absence of permafrost in this area.