Hypothesis 2 Paddy fields located at higher topographic
positions have higher tree densities than lower-lying fields.
In order to examine if the density of trees in paddy fields
is related to topographical position, GIS data on the spatial
distribution of all of the soil series in the region was
obtained from the Land Development Department of
Thailand (Table 1). Because each soil series in Northeast
Thailand only occurs in a specific physiographic position it
is possible to assign a topographic position to each paddy
field based on its particular soil series. Because the number