Figure 1: Distribution of the study used in the analysis across the tropical (23.5° North and 23.5° South latitude) and the sub-tropical (30° North and 30° South latitude) regions.

Studies are reported using graduate symbols classes corresponding to the number of N2O values (N. values) reported in each study. Map generated using ESRI 2011. ArcGIS Desktop: Release 10.1. Redlands, CA: Environmental Systems Research Institute.