Figure 6
National distribution of sampling stations and organic carbon contents. Map shows the: (a) national sampling stations including inland and coastal areas, and (b) organic carbon contents of inland and coastal areas with different precipitation. Colors of (a) and (b) are similar in both a and b maps4, 18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51. Areas followed by the same lowercase letters (a, b and c) are not significant at α = 0.05 (Duncan test). (Software of Adobe Illustrator CS 6, OriginPro 9.0, ArcGIS 10.2, and Microsoft Excel were used in drawing the figure. The outline of China was drawn by using ArcGIS (version 10.2) and referring to the map from http://map.ps123.net/china/5369.html).
