Horizon Vs. Layer Sampling in Forest Soils: Statistical Efficiency.

Forest soils typically exhibit high spatial variability. When performing studies aimed at detecting soil chemical differences in time, space or treatment an investigator may be required to collect a large number of samples to detect statistically significant differences. Since soils in particular horizons are, by definition, similar to one another, it may be statisically efficient to sample by horizon to minimize the number of samples necessary to detect a significant difference. I tested this hypothesis using data from the Hubbard Brook Experimental Forest, where samples were collected by depth and by horizon in the same pits. A total of 193 pits were sampled in four sampling years, one prior to a clear-cutting experiment and three after.