The effects of topography on soil climate (soil moisture and temperature) were previously investigated based on measurements from a few monitoring sites over a relatively short period. Here, we used high-frequency soil climate data over three years (2011-2013) collected from a sensor network to compare soil climate among topographic groups. The sensor network with 35 monitoring sites was established in the Shale Hills Critical Zone Observatory. At each site, soil moisture sensors were installed in various horizons to measure soil moisture and temperature at a 10-min interval. The monitoring sites were classified into south-facing steep slope, north-facing steep slope, south-facing swale, north-facing swale, valley, and ridgetop. Over the study period, ridgetop and steep slopes of both south- and north-facing sides are overall the driest, whereas the valley is the wettest. The impact of slope aspect on soil moisture varies at different slope positions. The north-facing slope is wetter than the south-facing slope throughout the year, which is likely due to a deeper infiltration depth and less incoming solar radiation and evapotranspiration. However, the two swale groups show no significant difference in the average and range of soil moisture as well as the wetting depth. The effect of slope aspect and gradient on soil temperature varies with time. In the non-growing season, the south-facing slope and swale receive more solar radiation and are warmer than the north-facing slope and swale. Nonetheless, in the growing season when the canopy can intercept much solar radiation, slope aspect has no significant influence on soil temperature. The influence of slope gradient on soil temperature is more evident in the growing season, when the valley is cooler than the ridgetop. However, in the non-growing season, snow cover might tradeoff the effect of less solar radiation received in the valley. The variation in soil temperature increases from the valley to the swales, the steep slopes, and to the ridgetop. The lower soil moisture plus less canopy cover in the ridgetop reduce the capability for soils to buffer heat fluctuations.
Wanghai Tao*, Li Guo, Quanjiu Wang, Henry Lin (2018): Effects of slope aspect and gradient on soil climate in a forested catchment revealed by high-frequency monitoring data from a sensor network. Abstract H21K-1804 presented at 2018 AGU Fall Meeting, Washington, D.C., 10-14.