Effects of plant root on nutritious elements transport in soil profiles of the Chinese Loess Plateau

Different plant roots may have potential impacts on nutritious elements movement in soil profiles. Distribution characteristics of fine root systems less than 1 mm in diameter in soil profile is the physiological basis of plants for adapting and improving adverse soil physical and chemical conditions. Few studies, however, have been conducted on the (nutritious) elements movement as affected by plant roots at profile scale. With the method of a large-size profile for (measuring) root density and an equipment of undisturbed monolith soil for measuring eluviation of elements, we investigated the transport intensity of nutritious elements, such as K, Na, Ca, Mg, Cu, Mn, Fe, Si, Al in the soil profiles as (affected) by root systems of different species of vegetation in hilly and gully regions of the Chinese Loess Plateau. The (objective) was to explore the approach to improve the biological effectiveness of soil nutrients. The results obtained (suggested) that transport differences among nutritious elements in soils were not depended on the amount of nutritious (elements) in soil rather than the distribution of plant roots of 1mm in diameters. The increased effects of roots on the nutritious (elements) movement in soil profile decreased as the soil depth increased. The effects of plant roots on nutritious element movement in soil profiles increased in the following order: forest landgrass landfarm land. The critical soil depth of different plant roots affecting elements transport in soil profiles was 30cm for forestry and 10cm for grassland. The movement of nutritious elements in soil profiles increased in the following order: CaNaMgKSiAl for the normal elements, and CuMnFe for micro-elements. The effects of plant roots on the nutritious elements movement in soil profile were weak when the effective root density of tree and grass were less than 17 and 60 roots per 100 cm~2 and root weight of tree and grass were less than 0.11 and 0.16 g per 100 cm~3 respectively. Plant roots can influence the nutritious elements movement in soil profile when the effective root density of tree and grass increased from 17 to 66 and from 60 to 106 roots per 100 cm~2 respectively, and root weight of tree and grass increased from 0.11 to 0.37 and from 0.16 to 0.30 g per 100 cm~3 respectively. Plant roots can significantly influence the nutritious elements movement in soil profile when the effective root density of tree and grass were more than 140 and 200 roots per 100 cm~2, and root weight of tree and grass were more than 0.70 and 0.40 g per 100 cm~3 respectively.