Topography-Controlled Soil Water Content and the Coexistence of Forest and Steppe in Northern China

作者：Hongyan Liu, Siyuan He, Oleg A. Anenkhonov, Guozheng Hu, Д. В. Санданов, N. K. Badmaeva · 发表于：Physical Geography · 年份：2012 · DOI：10.2747/0272-3646.33.6.561 · 被引用次数：51 · 研究领域：Plant Water Relations and Carbon Dynamics、Tree-ring climate responses、Ecology and Vegetation Dynamics Studies

The semi-arid forest-steppe ecotone in China is characterized by a patchy pattern of forest and steppe, with forest patches restricted to shady slopes. To address the effect of topography on forest distribution through regulation of available water, we calculated evaporation as a function of slope aspect and inclination. Field vegetation records from randomly selected sites with minimum slope inclination were used to test the simulated forest distribution. Seasonal and diurnal changes of surface soil temperature and moisture of shady and sunny slopes were recorded. Soil water content was measured during two growing seasons on both sunny and shady slopes with the same forest type at three sites located along the mean annual precipitation (MAP) gradient. Evaporation decreases with slope inclination on shady slopes, but increases with inclination on sunny slopes. The shady slope received 35% of the annual direct solar radiation received by the sunny slope when the slope inclination was 25°, and the contrast in annual direct solar radiation between the shady and sunny slopes further widens as slope inclination increases. Steeper shady slopes can support forests in dryer climates, with log-linear regression revealing a minimum slope inclination for forest distribution along the MAP gradient. The simulated minimum slope inclination for forest growth was larger than the observed minimum inclination, and the difference was greater in wetter conditions. A larger forest area fraction w...