| Summary: | Studies of soil heat regime are commonly confined to one vertical soil profile. Some studies on the basis of short-term temperature data series reported significant horizontal variation of topsoil horizons due to spatial variation in tree stand densities, plant cover and soil cover heterogeneity. Introduction of programmed automated temperature data loggers facilitated studies of horizontal heterogeneity in soil temperature, i.e. so called temperature fields with long temporal data series. However horizontal variation of soil temperature has not practically been studied in most Russian ecosystems, including those in the West Siberian northern taiga zone. The study of soil temperature regime was carried out in the environs of Noyabrsk (Yamalo-Nenetsky Autonomous Region, Russia) in the four key study sites: climax larch (Larix sibirica Ledeb.) and Scots pine (Pinus sylvestris L.) forests, and flat palsa mire (separately palsa and adjacent hollow). On each study site automated temperature data loggers were used in 5 replicated subsites to measure soil temperature with 0.5°С and record it every 4 hours, i.e. at 1, 5, 9, 13, 17 and 21 o’clock, daily. The loggers were placed at 10 cm soil depth in the root zone. The data from the meteorological station in Noyabrsk were also used in the study. The standard deviation of temperature values, recorded in a study site at one time point, was used as a measure of temperature variation. In all study sites the maximal temperature variation was observed at the beginning of the warm season. In both forest sites soil temperature began varying already after snow thawed, which was most likely due to the heterogeneity of vegetation cover and forest litter; in the pine site soil the heterogeneity of direct solar radiation as a result of the crown shadowing also contributed to temperature variation. The biggest soil temperature variation during this period was observed at the pine forest site, with difference between simultaneous replicated measurements reaching at certain time points ...
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