Spatial Variability Characteristics of Soil Available Mn and Zn in the Middle Reaches of Tuojiang River Basin

The available states of Manganese (Mn) and zinc (Zn) in soil exert important roles in same biochemical reactions. Their deficiency can result in plant micronutrient disorders, but the excess contents may contribute to several environmental issues. Their spatial distribution and influential factors in the middle reaches of Tuojiang River Basin, a typical region with the broken terrain and densely populated hill, were studied with the combination of statistics, geostatistics, global positioning system (GPS) and geographic information system (GIS). According to the data of the contents in topsoil (0~20 cm) from the 296 random sampling points,the contents of soil available Mn and Zn were 5.95 and 1.05 mg kg-1, respectively. The highest value regions (>11 mg kg-1) of Mn contents were mainly distributed in the central parts of study area, and first decreased to the both sides from the central and then increased towards the northwest. The highest value regions (>1.8 mg kg-1) of Zn contents were mainly distributed in the northwest parts, and then reduced gradually towards to the southeast and southwest presenting zonal shapes. Almost 30% of the area had higher than 50% probability to exceed the threshold value (7.00 mg kg-1) of the soil available Mn based on probability kringing, Similarly, more than 70% part of the area with the probability more than 50% exceed the threshold value (0.50 mg kg-1) of soil available Zn. The content and spatial distribution of soil Mn and Zn were affected by parent materials, landform types, slopes, landuse patterns, textures, pH and organic matters (OM). While the above factors except for OM and texture (P>0.05) had significant influence on soil available Mn (P