Influence of forest clear‐cutting on the thermal and hydrological regime of the active layer near Yakutsk, eastern Siberia

Abstract

[1] Thermal and hydrological conditions in the active layer were investigated at a mature larch forest and an experimental cutover, to clarify the characteristics of heat and water budget in the active layer and to assess the influence of clear-cutting on permafrost and active layer conditions. Clear-cutting enhanced ground thawing and the difference in the active layer thickness between the forest and the cutover after 1 year was 14 cm. The soil water content drastically decreased at the forest, while that at the cutover was retained during the first thaw season after clear-cutting. Although the ground heat flux continued to increase at the cutover (the difference in the total amounts between sites from May to August were 44 and 69 MJ/m 2 in 1 year and 2 years after the clear-cutting, respectively) marked changes in the active layer conditions were limited only to the first thaw season. The correspondent differences in the active layer thickness between the sites were 16 and 14 cm in 2 years and 3 years, respectively. Further increases in the maximum thaw depth at the cutover site were inhibited by the thermal inertial effect of the larger amount of ice in the second spring after disturbance. This suggests a self-retention mechanism of the active layer thickness after forest disturbance in this continuous permafrost zone.

Variations of Microwave Scattering Properties by Seasonal Freeze/Thaw Transition in the Permafrost Active Layer Observed by ALOS PALSAR Polarimetric Data

“…However, some polarimetric parameters, including the dominant eigenvalue and co-polarization coherences exhibit characteristic differences between two ground sites only in frozen conditions. According to the literature [23][24][25][26][27], soils and active layers in forested areas are distinctive from those in open areas by the thermal condition, active layer thickness, infiltration and evaporation rates, salinity and thickness of the shielding layer. Consequently, although the causal mechanisms about these characteristic scattering properties cannot be confirmed at this stage, polarimetric scattering analysis also reveals the possibility of obtaining a spatially-detailed distribution of the surficial features.…”

“…In this study, a small part of the area showing distinctive differences in the radar-derived spring transition date is selected for further investigation of microwave scattering properties. The permafrost characteristics in the Yakutsk area have been relatively well studied as compared to other high-latitude regions [23][24][25][26][27]. This region is covered with forests, grasslands and thermokarst features underlain by continuous permafrost.…”

“…Two test sites from taiga forests, F1 and F2, were selected to have different types of trees based on the Landsat image in autumn. They are identified as evergreen trees, such as pine (F1), and deciduous trees, such as larch (F2) [23][24][25][26]. According to the literature [25,30], two sites in the upper right quadrant of the image, S1 and G1, correspond to the recently-burnt taiga (three years or less) covered with shrub (S1) and low or no vegetation (G1), respectively.…”

The variability of radiative balance elements and air temperature over the Asian region of Russia

“…Stations (1976( -2005( ) JRA-25 (1979 T , trends are revealed in March, May, June, July, August and October. Over Asian territory of Russia temperature field variability is also characterized by significant spatial inhomogeneity.…”

“…However, studies dedicated to heat and radiative fluxes investigation over ATR, especially during last decades, do not provide complete information for the territory, only for local regions (Zotino, Yakutsk) and these studies are connected with solution of specific problems (Meroni et al, 2002;Tchebakova et al, 2002), for the regions of the North and wetlands (Meroni et al, 2002;Iwahana et al, 2005;Boike et al, 2008).…”