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

Hydrological service by soil under mountain ecosystems is a hot topic in current ecological research. We monitored the precipitation and soil moisture dynamics and measured the soil hydrological parameters of grassland and forest ecosystems along an elevation gradient in the Dayekou catchment of the central Qilian Mountains in northwestern China. Soil moisture dynamics in response to rainfall events exhibit different characteristics with different ecosystems and at different elevations. The soil conditions (including soil texture, soil structure, and soil hydrological parameters), the local meteorological condition, and the physiological characteristics of the vegetation can help explain eco-hydrological differences. The total rainfall increased with an increase in elevation across the rainy season. Soil moisture content increased with an increase in altitude and differs with land cover on average values. Grassland and forest at low elevations have 50% and 41.7% of the soil moisture content level under shrubland at high elevations, and Qinghai spruce forest soil has the greatest “green water (the water used mainly by the ecosystem itself)” capacity. Fluctuation in soil moisture diminishes with increased depth, yet the trend is not obvious under shrubland at high elevations. The sensitivity of soil moisture response to rainfall differed depending on land cover and soil depth. Soil moisture under alpine shrubland is far more sensitive to single rainfall events, whereas other land-cover types display only typical responses in periods of frequent rainfall events (continued-rainfall scale). The study of soil moisture dynamics contributes to research on hydrological service in mountain ecosystems, and is helpful in promoting knowledge innovation regarding the relationship between water and ecosystems.