Geostatistical techniques were used to quantify the scale and degree of soi
l heterogeneity in 2 m(2) plots around 9-year-old poplar trees and within a
wheat field. Samples were taken during two years, on an unaligned grid, fo
r analysis of soil respiration, C and N content, available P, gravimetric m
oisture, pH, nitrification potential, and root biomass. Kriged maps of soil
respiration, moisture, and C content showed strong spatial structure assoc
iated with poplar trees but not with wheat rows. All soil properties showed
higher autocorrelation in June than in April. Isopleth patchiness for all
variates was less in June. This was associated with lower respiration rates
due to lower litter decomposition. From the degree and scale of heterogene
ity seen in this study, we conclude that the main causes of soil heterogene
ity at this scale (2 m(2)) are likely to be found at micro scales controlle
d in part by plant root and plant residue patterns. These must be understoo
d in the evaluation of ecosystem processes.