Abstract: By using geostatistic method, this paper studied the spatial distribution patterns of the active mounds of Solenopsis invicta Buren polygyne populations in Wuchuan and Shenzhen, and built up the spherical models of the interval distances and semivariances of the mounds. The semivariograms were described at the two directions of east-west and south-north, which were obviously positively correlated to the interval distances, revealing that the active mounds in locative area were space-dependent. The ranges of the 5 spherical models constructed for 5 sampling plots in Wuchuan were 9.1 m, 7.6 m, 23.5 m, 7.5 m and 14.5 m, respectively, with an average of 12.4 m. The mounds of any two plots in this range were significantly correlated. There was a randomicity in the spatial distribution of active mounds, and the randomicity index (Nugget/Sill) was 0.7034, 0.9247, 0.4398, 1.1196 and 0.4624, respectively. In Shenzhen, the relationships between the interval distances and semivariances were described by 7 spherical models, and the ranges were 14.5 m, 11.2 m, 10.8 m, 17.6 m, 11.3 m, 9.9 m and 12.8 m, respectively, with an average of 12.6 m.

Key words: OLAND, Biological nitrogen removal, Dissolved oxygen