Methodology >> Plot System
The permanent plot system was established in 1935 by the U.S. Forest Service when they managed the HMF. Square 0.25-acre plots were established in a 5-acre rectangular grid pattern (330 feet along E-W lines and 660 feet along N-S lines) covering the entire Forest. The USFS inventoried all woody stems (greater than 1/2" diameter at breast height (DBH)) in each of the permanent plots, recording the measured diameters of all individuals by species in 1-inch diameter classes in those plots supporting forest communities. The shrub and herb layers were analyzed in 10 "milacre" (1/1000-acre) plots in one corner of the larger tree-layer plot.
The HMF permanent plot system has been expanded with the addition of lands since 1935 to include the Moon Lot and the Robinson-Towers Tract in MA and the Samuel Humes, the Prindle, and the SBA tracts in NY as they were added to the HMF. The plot system has been inventoried in the early 1970s (1971-5 was expanded to 330 plots) and again in the mid 1990s (1994-6 expanded to 440 plots) by H.W. Art and teams of many students. The HMF permanent plot system now represents one of the finest long-term data bases on "unmanaged" deciduous forests in the world. It is expected that the periodic reinventory of the system will recur at 15-year intervals.