Soil conservation value flow processes of two typical grasslands

Grassland is the largest land resources by area in China. It plays an important role in food production, carbon fixation and sequestration, O2 release, soil and water conservation, water supply, nutrient recycling, entertainment, and biodiversity sustaining, among which, soil conservation is one of the most essential services delivered by grassland ecosystem. There have been few studies specially focusing on soil conservation value of grassland ecosystem till now, although soil conservation has historically been emphasized in the practice of grassland management, resulting in limited understanding about the mechanism of soil conservation of grassland especially at spot scale. Therefore, the dynamic flow processes of soil conservation value of grassland at spot scale are urgent to be researched. In the context, the study targeted at the dynamic processes of soil conservation of two kinds of typical grasslands: Neimenggu Temperate Grassland and Haibei Alpine Meadow. Due to that soil erosion of both the selected grassland ecosystems was mainly caused by wind, on the basis of simplicity and scientificity, we chose the Pasak wind erosion model and improved it through the input of factors to assess wind induced soil erosion. The accuracy of the model was tested by the existing research results of other scientists. Related data were from Chinese Ecosystem Research Net (CERN). The soil conserved by grassland was the subtraction of soil eroded under vegetation coverage the actual soil erosion, from the soil eroded without vegetation the potential soil erosion. The soil conservation value was calculated using the method of shadow price and opportunity cost. The results showed that the soil conservation service supplied by grassland ecosystems was discrete, which was highly related to the wind velocity and vegetation coverage. The annual soil conservation value of Neimenggu Temperate Grassland was at 1.06× 104 ¥/hm2,while that of Haibei Alpine Meadow was at 1520 ¥/hm2. The soil nutrient conservation was dominant in soil conservation service, contributing as high as 99% to the total soil conservation value. Both the potential and actual soil erosion of Neimenggu Temperate Grassland was higher than those of Haibei Alpine Meadow in a year. And the annual soil conservation value of Neimenggu Temperate Grassland was far bigger, 7 times as much as that of Haibei Alpine Meadow. The soil conservation service of grasslands was distributed differently in each season. The potential and actual soil erosion and the soil conservation in Neimenggu Temperate Grassland mainly happened in spring and autumn, while in Haibei Alpine Meadow the potential and actual soil erosion mainly occurred during December to April in the next year and the soil conservation in spring and summer. It was concluded that the soil conservation value of grassland has a clear changing pattern during a year with wind velocity and vegetation coverage. The high soil conservation value of grasslands under wind, especially in the sandy areas, calls upon us to take efforts to save grassland from destruction and keep grassland healthy.