Absolute (a) and relative (b) concentrations of nitrate, ammonium and amino acids in 1 M KCl extracts of soil. Absolute concentrations are expressed per gram dry mass of soil. Replicate soil samples were collected adjacent to each of three Eucalyptus species at each of three sites on four occasions. Absolute and relative amounts of nitrate, ammonium and amino acids did not differ depending on which species they were collected next to (ANOVA, P > 0.05), or between the three sites; hence data for species and sites are combined. Each data point is the mean of 27 replicates; error bars are standard errors. At all dates there were significant differences among N-forms (ANOVA, P < 0.05), thus the significance of differences between pairs of means was determined by a post hoc test (LSD) and is indicated by superscripted letters.