Exotic, invasive earthworms are known to translocate and consume forest floor material, depleting the duff layer, which is an important germination and rooting medium for herbaceous plants. As a result, the diversity of plants in deciduous forests in the northern tier of the US is threatened. Secondary succession forests in RI support exotic earthworm populations. While alteration of soil vertical structure in these forests can be extensive, removal of forest floor material is variable even within a forest stand. To the touch soils with a duff layer are more easily compressed than soils without a duff layer. To assess the variability of forest floor depletion in invaded forests, pocket penetrometers were used to measure compressive strength along 5 to 6 m-long transects at intervals of 5 to 10 cm. The data was analyzed using classical statistics and second order statistics. As expected, compression strength was greater in soils with high earthworm densities. Spatial variability of compression strength was less when earthworm densities were high. Variogram analysis showed that compressive strength of soils with earthworms were autocorrelated over a longer range than soils without worms.