The method used in the earliest collections at the HBEF by Gosz et al.
Federer's method differs from that of Siccama in the HBEF study.
Five forest-floor samples were collected from random locations in each stand, using Siccama's method, as described above (see HBEF).
Organic matter concentrations in the forest-floor samples from the Hubbard Brook Experimental Forest (HBEF) averaged 54%.
The sampling methods at the HBEF were the most intensive of our three studies, involving from 52 to 87 blocks, each 15 X 15 cm, at each sampling date.
The goal of analyzing samples collected over a period of 21 yr at the Hubbard Brook Experimental Forest (HBEF) was to describe changes in Ca and Mg concentrations and content since the previous measurement of forest-floor chemistry in 1969-1970 (Gosz et al.
Results from the intensively sampled stand at the HBEF were consistent with the stands of similar age in the chronosequence: decreases in concentrations of Ca were more pronounced than were the changes in contents.
A different danger in experimental design is illustrated by our early comparison of two sample collections at the HBEF Studies of change in soils over time are often based on only two points in time (Johnson et al.
Calcium concentrations in precipitation at HBEF decreased fairly steadily from 1965 through 1983, and then increased slightly from 1983 through the early 1990s (Likens et al.
At HBEF, exchangeable Ca, Mg, and K in the forest floor all decreased by 40% in the first 3 yr after whole-tree harvest (Johnson et al.