How plant production in the Mongolian grasslands is affected by wind-eroded coarse-textured topsoil

Abstract While it is known that soil erosion by wind in drylands results in soil loss and redistribution and changes the texture of topsoil, there is little information about how these changes in the topsoil might affect the productivity of vegetation and if they result in degradation of the grasslands in wind-eroded regions such as Mongolian grasslands. In this study, we compared two different scenarios of vegetation growth, namely a wind-eroded scenario and an actual field condition, on two different grasslands in Mongolia (steppe and desert steppe) using an ecosystem model. The simulations of the wind-eroded scenario were based on a topsoil (0–0.1 m depth) with 1% clay and 99% sand, designed to represent an extremely wind-eroded soil surface that had permanently lost the fine clay particles and had gained sand particles. The effects of temperature, nutrient and water stresses on plant production were quantitively estimated. The model gave reasonably good simulations of the vegetation and soil water dynamics during the growing seasons (April–September) from 2002–2011. The simulation results showed that water had more effect on plant production than nitrogen and temperature at the two sites, and stresses because of a lack of water and nutrients generally affected plant production in the wind-eroded coarse-textured topsoil. Plant production was 20.2% lower in the wind-eroded scenario than in the actual field condition in the desert steppe under water-stressed conditions but plant production was slightly higher (5.0%) in the wind-eroded scenario on the steppe that received more rainfall, because of a reverse texture effect, where water continues to infiltrate from the coarse topsoil (0–0.1 m depth) to the deeper root-zone (0.1–0.3 m depth) because of lower evapotranspiration from soil, and facilitates growth. When this happens, there is enough soil moisture in the root-zone, and plant growth is mostly affected by the nitrogen supply.