Forests cover 60% of the land area of Massachusetts, but most are less than 120 years old, having regenerated after past heavy cutting and hurricane blowdown. In 2006, the Massachusetts Executive Office of Energy and Environmental Affairs set aside 20,235 ha of state forestland as large forest reserves, with the objectives of conserving native biodiversity and having only natural succession and natural disturbance control future forest development. A long-term ecological monitoring (LTEM) program was established to assess the condition and successional status of the forest reserves, and to make comparisons with the limited area of old-growth stands in Massachusetts.

In the 1950s, Massachusetts forestry agencies established Continuous Forest Inventory (CFI) plots on all state forest lands, mainly to monitor the ongoing timber harvesting program. These plots were designed for measuring live-tree variables at 10-year intervals. In 2000, the CFI system was modified to collect a broader range of ecological data including snags and coarse woody debris. These plots also serve as the monitoring system for the new reserves. We used the 2000 CFI dataset to compare the structure of the forest reserves to that of old-growth stands.

Results/Conclusions

A total of 453 ha of old-growth forest in 33 stands have been identified in Massachusetts. Old-growth stands had by definition at least 5 trees/ha greater than 225 years old, whereas reserve plot ages ranged from 38 to 121 years (mean of 88.5 years). Compared to old-growth stands, reserves had less live aboveground biomass (203.6 vs. 288.9 Mg/ha, p≤0.0001). There was no difference in stem density for live trees ≥12.7 cm dbh (diameter at breast height), but there were fewer large live trees (dbh ≥ 50 cm) in the reserves (16.3 vs. 56.1 stems/ha, p≤0.0001). Although there was no difference in total snag volume and density, mean snag dbh was less for the reserves (24.6 vs. 35.6 cm, p≤0.0001) and there were fewer large snags (dbh ≥ 35 cm) (5.2 vs. 13.4 stems/ha, p≤0.0039). There was much less coarse woody debris (21.5 vs. 135.2 m3/ha, p≤0.0001) in reserves than in old-growth stands. Thus, the primary differences in reserve and old-growth structure are less aboveground biomass, fewer large live trees and large snags, and lower volumes of coarse woody debris. These data provide a baseline comparison for tracking future changes in the reserves.