Distribution characteristics of iron, carbon, nitrogen and phosphorus in the surface soils of different land use types near Xingkai Lake

Abstract

The purpose of this study was to research the differences in iron, phosphorus, nitrogen and organic matter contents at two soil depths in areas with different land use types in the Xingkai Lake National Nature Reserve and to determine the causes of those differences. Additionally, this study sought to analyse the correlations between the contents of different nutrients and to determine the reasons for those correlations. Five typical land use types, namely, lakeshore sandy land, grassland, forestland, dryland and wetland, were selected in the Xingkai Lake National Nature Reserve. The contents of amorphous iron (Feo), complexed iron (Fep), dithionite-extractable iron (Fed), total iron (TFe), total phosphorus (TP), total nitrogen (TN) and organic matter (OM) were measured in these soils at two depths: 0–5 cm (soil depth 1) and 5–10 cm (soil depth 2). For soil depth 1 and soil depth 2, the land use type had no significant effect on the element contents. For the entire soil depth range (0–10 cm), the land use type had the most significant impact on the TP content (p < 0.01). Furthermore, soil depth had a significant effect on the contents of Feo (p < 0.01), TP (p < 0.01) and OM (p < 0.05). Overall, the element content at soil depth 2 was higher than that at soil depth 1. The interaction between land use type and soil depth significantly influenced the contents of TN and OM (p < 0.05). The contents of TN and OM in the lakeshore sandy land and dryland were high, and the contents of TN and OM were highly positively correlated (r = 0.90652, p < 0.01). Different land use types caused different degrees of disturbance in the soil, resulting in differences in the element contents in the soils. The differences in the distribution of soil element contents in the topsoil were the result of important natural and human factors.