Plant root system distribution and its effect on soil nutrient on slope land converted from farmland in the Loess Plateau

In order to understand the root system distribution of Stipa bungeana in the soil profile and its influence on soil nutrients, two slopes were studied. One is a slope with 30 years growth of Stipa bungeana and the other is a bare slope land. They are all located in Shenmu experiment station of the Loess Plateau. The soil nutrients and root distribution in the soil profile were studied using picture management software and general analysis method. The results show that the root of Stipa bungeana mainly distributed in the soil profile of 0-50 cm and it could be simulated by an exponential function. The contents of organic matter, total nitrogen, total phosphorus, nitrate nitrogen and ammonium nitrogen on the soil surface with plant root were higher than those on the soil surface without root. The organic matter, total nitrogen and nitrate nitrogen have obvious topsoil accumulation when the soil contains roots. The changes of organic matter, total nitrogen and nitrate nitrogen in 0～50 cm along the depth of soil can be described by a power function, but the total phosphorus can be described by a linear function, and the changes of soil nutrients along the root length density can be described by linear function.