History and Overview

Natural disturbance in the Acadian forest of the Northeastern U.S. is dominated by gap dynamics with a 1% annual frequency. Two expanding-gap silvicultural treatments were designed based on this pattern of natural disturbance, and build upon a 50-year study of classical even- and uneven-aged silvicultural methods by the U.S. Forest Service on the Penobscot Experimental Forest. The Acadian Forest Ecosystem Research Program (AFERP) was initiated in 1993 to examine the stand dynamics and ecological effects resulting from the use of these expanding-gap treatments. The treatments include: 1) 20% canopy removal on a 10-year cutting cycle (creating 0.2 ha openings), a 10-year regeneration window between expansions, and a 50-year rest period following the first five cycles; and 2) 10% canopy removal on a 10-year cutting cycle (creating 0.1 ha openings), 20-year regeneration window between expansions, and no rest period.  A network of dispersed permanent reserve trees (equaling 10% of pre-harvest basal area) is being maintained as a biological legacy in both treatments.  Each treatment is being compared to an unharvested control where natural processes predominate.  The experimental units are about 10 ha in size and replicated three times in a randomized block design. During the past decade, the influence of the treatments on stand dynamics, understory vegetation, downed woody debris (DWD), songbirds, amphibians, arthropods, and epiphytes have been examined. Gap harvesting influenced the amount of DWD, and increased vegetation abundance and diversity relative to natural gaps and undisturbed canopy.  Songbird communities were largely unaffected by the initial gap openings. Amphibian and arthropod communities, however, were affected by DWD piece size and location relative to harvest gaps. Epiphyte and associated invertebrate communities were influenced by whether the host tree was near a harvest gap.

The nine research areas are 8.7 – 11.3 ha and have fifteen or twenty 0.05 ha permanent, circular sampling plots for baseline monitoring.  Overstory, sapling, and herbaceous communities, canopy light levels, and forest floor samples are monitored or collected with these plots.  These plots are laid out on a 50-by-50 meter grid; the center of each plot is marked by an orange-capped rebar stake.  Plots are coded alpha-numerically.  Deadwood dynamics, retention tree growth and survival, and gap vegetation are each monitored separately in specialized inventory designs.

Caption: Field tour of AFERP research areas 5 & 6 during 2006-2007 winter harvest.  From left to right: Mike Saunders (former AFERP manager), Bob Wagner (AFERP director), Greg Hertz (contract logger), and Bob Seymour (one of the original founders of AFERP).  The group is standing within a recently created gap in research area 5 (10-20 treatment).