Effects of deforestation and weather on diurnal frost heave processes on the steep mountain slopes in south central Japan

Abstract

Freezing and thawing processes play an important role for the gravitational transport of surface materials on steep mountain slopes in Japan. The effects of deforestation on frost heave activity were observed through the 2012/2013 winter season in Ikawa University Forest, a southern mountainous area in central Japan (1180–1310 m above sea level). During periods without snow cover, needle ice development prevailed at a clear‐cut site, and the downslope sediment movement of upper soil was 10 to 15 cm through the winter season. At a non‐cut site, rise and fall in the ground surface level prevailed on a weekly scale, with no evident downslope movements at the surface; ice lens formation in the soil layer is assumed. Abrupt changes in the radiation budget, such as the strengthening of nighttime radiative cooling and increases in daytime direct insolation, induced frequent development/deformation of needle ice at the clear‐cut site. In snow‐free periods, the day‐to‐day variability in needle ice growth length and in nighttime averaged net radiation showed significant correlations; cloudy weather with warmer and moist air intrusion associated with synoptic disturbances prevented the occurrence of needle ice. Namely, day‐to‐day weather changes directly affected the mass movement of the upper soil after deforestation. Shallow snow cover occurred discontinuously through the winter and is likely an important factor in keeping the soil moisture sufficiently high in the upper soil layer for initiating needle ice during snow‐free periods. We also discuss contributions of coastal extratropical cyclone activities providing both snow cover and cloudy weather in the southern mountain areas of central Japan to the intra‐seasonal variability in frost heave and its indirect effect on soil creep and landslides on the deforested steep slopes. Copyright © 2015 John Wiley & Sons, Ltd.

Forest harvesting impacts on micrometeorological conditions and sediment transport activities in a humid periglacial environment

“…Air temperatures frequently rise above and fall below 0 degrees during the winter (Ueno et al, 2015;Imaizumi et al, 2017).…”

“…1c). A 0.87-ha area in the upper part of the study 20 area, called clear-cut (CC) site in this study, was harvested during March-September 2012 (Ueno et al, 2015). Logging was conducted by skyline yarding to avoid damaging the slope surfaces by dragging logs.…”

“…causes large vegetation changes in mountain areas (Imaizumi et al, 2012;Ueno et al, 2015;Goetz et al, 2015). The impact of forest harvesting on the sediment transport process is possibly significant in periglacial areas, where sediment transport activities are highly controlled by micrometeorological conditions (e.g., air and ground temperatures, ground water conditions) (Matsuoka, 2001;Boelhouwers et al, 2000;Harris et al, 2008b).…”

“…Tree crowns intercept rainfall and reduce the volume of precipitation reaching the ground (Xiao et al, 2000;Fan et al, 2014). The tree crown also controls net radiation and ground temperature (Ueno et al, 2010;Ueno et al, 2015). Sediment transport triggers, such as changes in soil moisture, generation of overland flow, and freeze-thaw of ground 10 water, are affected by these micrometeorological conditions (Wainwright et al, 2000;Gray et al, 2002;Ueno et al, 2015).…”

“…Gravitational sediment transport processes (e.g., soil creep and dry ravel), which have been poorly studied in relation to vegetation change, are more important sediment transport processes than surface wash because of the steep terrain (Imaizumi et al, 2017). Ueno et al (2015) showed that the type of winter solifluction changes from frost creep to needle-ice creep following forest harvesting in the Southern Japanese Alps, because…”