Quantification of soil spatial and temporal variability at watershed scale is important in ecological modeling, precision agriculture, and natural resources management.

In order to provide information for land management and control of environmental issues, Dr. YANG Xiaolin of Institute of Mountain Hazards and Environment, Chinese Academy of Sciences (IMHE) investigate the spatio-temporal variations of soil nitrogen under different land uses in a small watershed in the hilly area of purple soil at the upper reaches of the Yangtze River in southwestern China by using conventional statistics, geostatistics, and a geographical information system.

Dr. YANG and his team collected a total of 552 soil samples (0 to 15 cm) from 276 sites within the watershed in April and August of 2011, and analyzed soil total nitrogen (STN) and nitrate nitrogen (NO3-N). They also compared spatial variations of STN and NO3-N under different land uses as well as the temporal variations in April (dry season) and August (rainy season).

Results showed that the spatial characteristics of soil nitrogen were greatly affected by land use, and the mean STN contents were in the following order: paddy field > forestland > sloping cropland. Temporally, no significant difference was found for STN in both dry and rainy seasons, but the great decrease of NO3-N was observed in rainy season for all the land use types. Nitrogen movement, transformation, absorption of plant were the key processes influencing soil nitrogen contents at spatial and temporal scales, but the dominated process controlling the temporal variations of soil nitrogen might be different for different land use types.

The paper entitled “Spatial and Temporal Patterns of Soil Nitrogen Distribution under Different Land Uses in a Watershed in the Hilly Area of Purple Soil, China” was published in Journal of Mountain Science,(2013)10(3):410–417, DOI: 10.1007/s11629-013-2712-7.