Synergistic effect of vegetation and air temperature changes on soil water content in alpine frost meadow soil in the permafrost region of Qinghai‐Tibet

Abstract

Abstract:Seasonal changes over 2 years (2004)(2005)(2006) in soil moisture content ( v ) of frozen alpine frost meadow soils of the QinghaiTibet plateau permafrost region under three different levels of vegetation cover were investigated. Vegetation cover and air temperature changes had significant effects (synergistic effect) on  v and its distribution in the soil profile. During periods of soil freezing or thawing, the less the vegetation cover, the quicker the temperature drop or rise of soil water, and the shorter the duration of the soil water freeze-thaw response in the active soil layer. Under 30% and 65% vegetation cover the amplitude of variation in  v during the freezing period was 20-26% greater than that under 93% cover, while during the thawing period, it was 1Ð5-to 40Ð5-fold greater. The freezing temperature of the surface soil layer, f T s , was 1Ð6°C lower under 30% vegetation cover than under 93% vegetation cover. Changes in vegetation cover of the alpine frost meadow affected  v and its distribution, as well as the relationship between  v and soil temperature (T s ). As vegetation cover decreased, soil water circulation in the active layer increased, and the response to temperature of the water distribution across the soil profile was heightened. The quantity of transitional soil phase water at different depths significantly increased as vegetation cover decreased. The influence of vegetation cover and soil temperature distribution led to a relatively dry soil layer in the middle of the profile (0Ð70-0Ð80 m) under high vegetation cover. Alpine meadow  v and its pattern of distribution in the permafrost region were the result of the synergistic effect of air temperature and vegetation cover.

Soil moisture dynamics of typical ecosystems in response to precipitation: A monitoring-based analysis of hydrological service in the Qilian Mountains

“…The soil bulk density, organic carbon content, soil texture (sand, silt, and clay) and field water capacity were measured, and the soil porosity was calculated, which may have a close relationship with soil moisture dynamics (Simunek et al, 2005;Wang et al, 2008;S. Wang et al, 2013).…”

Effects of Urbanization and Seasonal Cycle on the Surface Urban Heat Island Patterns in the Coastal Growing Cities: A Case Study of Casablanca, Morocco

“…This relationship is more significant in municipalities and region coinciding with important density of built up or industrial areas experiencing important air pollution emissions (Figure 5a-c The interpretation of the satellite images shows also that during winter the daytime SUHII in the urban area become more significant when air temperature exceeds the average winter temperature which ranges from 15 to 16.5 °C as shown in Figure 5a-c (with minimum air temperature of approximately 13 °C). The presence of low outdoor temperature contributes significantly to reducing soil moisture deficit [47,93,94], which is more sensitive to air temperature than precipitation [47], and hence to reducing the emergence of daytime SUHII in the permeable cover of urban core characterized by partial vegetation cover. The result illustrated in Figure 5d accentuates this effect and shows a weak SUHII in Casablanca region on 3 January 2015, since that day, and during the consecutive three previous days, the Casablanca region had air temperature below winter average temperature (average air temperature in the neighborhood of 11.5 °C with air temperature of approximately 6.4 °C at 8 am which correspond to the half of minimum temperature of Figure 5a-c).…”

Reply to Lofgren, B.M.: Comment on Hicham Bahi, et al. Effects of Urbanization and Seasonal Cycle on the Surface Urban Heat Island Patterns in the Coastal Growing Cities: ACase Study of Casablanca, Morocco. Remote Sens. 2016, 8, 829

“…Figure 5d accentuates this fact and illustrates a weak SUHI due to the important decrease in air temperature compared to the threshold mentioned above. Some research shows that the presence of low outdoor temperature keeps moisture in the soil as long as possible [3][4][5] and then contributes in controlling the cooling effect. Hence, it was concluded that air temperature controls soil moisture and the response of soil moisture to air temperature is more sensitive than precipitation [3].…”