Vertical variations of soil moisture and total nitrogen in small catchment on Loess Plateau

This study was to investigate the vertical distribution and variations of soil moisture and soil total nitrogen under different vegetation types on the Loess Plateau. Soil moisture and soil total nitrogen in 0-800 cm profile under five vegetation types, i.e., alfalfa, wild grass, crop, caragana and pine, were measured and analyzed. Soil moisture had a remarkable stratified distribution in the vertical direction, with vicissitudinary dry and wet layers. The vertical distribution of soil moisture was affected by vegetation type. Different vegetation type had different occurrence depth of relatively dry and wet layers and different average soil moisture. Cropland and grassland performed better in soil water retention. Soil moisture of these two vegetation types showed greater vertical variation. The two planted vegetation types, alfalfa and caragana, consumed much more soil water, and thus did not have a pronounced vertical variation in soil moisture. Soil moisture under pine trees had middle value and moderate variation extent. Soil total nitrogen of the study area was low, with a sudden decline in top 20 cm layer and still gently decreased below 20 cm depth. Soil total nitrogen was higher under caragana than those under other four vegetation types.