By William B. Leak and Mariko Yamasaki, U.S. Forest Service, Northern Research Station, Durham, NH, and Karen P. Bennett, UNH Cooperative Extension
A field note is a report from "the field," based on observation and experience. This forestry field note grew out of the panel and discussion “How Resilient Are New England Forests After Biomass Harvesting?” held at the New England Society of American Foresters Annual Meeting in March 2014. For copies of the presentations and notes from the discussion.
Concerns over large-scale clearcutting, and especially whole-tree harvesting, have been with us since the late-1960s. Accelerated nutrient depletion is a primary concern (Bormann et al. 1968; Federer et al. 1989) based on preliminary scientific studies published in reputable journals. Also, there are general concerns over the early appearance of such harvests at both the landscape and hiking-trail levels. Concerns have risen since the increase in highly mechanized whole-tree harvesting systems and utilization of tops for biomass products.
The other side of the story is that clearcutting, with or without whole-tree harvesting, is efficient, highly appropriate in decadent stands, and required to provide habitat for a range of wildlife species (DeGraaf and Yamasaki 2003, DeGraaf et al. 2006, Rudnicky and Hunter 1993). Heavy or whole-tree harvesting also is an efficient means for regenerating a diverse range of trees along with the noncommercial species such as pin cherry (Prunus pensylvanica) and Rubus spp. that are important for wildlife. Some believe that natural disturbance provides the necessary habitat conditions. However, natural disturbance is hit-or-miss, and usually a light touch, on mid-elevation northern hardwood stands.
After decades of concern, recent information indicates that whole-tree harvests in northern hardwood stands do not cause depletion of calcium reserves (Campbell et al. 2007); this was based on a 15-year re-examination of a 54-acre whole-tree harvest at the Hubbard Brook Experimental Forest in Thornton, NH. Eight years after harvest, levels of exchangeable calcium, magnesium, and potassium also were unchanged (Johnson et al. 1997).
Biomass productivity in young hardwood stands (10 to 14 years old) in New Hampshire and western Maine was comparable between whole-tree and conventional harvests (Roxby and Howard 2013).
After 17 years, whole-tree harvests of spruce-fir in central Maine showed no indications of calcium depletion although there was some concern about the effects of acid deposition on magnesium and nitrogen (McLaughlin and Phillips 2006; Briggs et al. 2000).
How about positive effects? In addition to the items above (efficiency, decadent stands, habitat, regeneration), there are indications that heavy harvests can have a positive effect on trout food abundance and brook trout abundance (Noel et al. 1986; Nislow and Lowe 2003, 2006). This possibility requires more research to balance the positive effects of increased trout abundance and food with an associated negative effect of warmer water. Careful placement and usage of stream buffers, even narrow ones (Wilkerson et al. 2006, 2010), could provide an optimum solution.
In summary, based on current information, heavy clearcutting and/or whole-tree harvest does not cause nutrient depletion in New Hampshire and adjacent areas. However, there are some precautions that must be observed:
- Most of the conclusions described above are based on the assumption of normal rotations of 80 to 100 years plus or minus. Very short, repeated rotations could produce different effects.
- Most of the work was done on soils with moderate or better soil textures. It is possible that different results would be found on sandy, coarse outwash soils or areas of shallow bedrock (Hallett and Hornbeck 2000). Often, these are areas supporting oak-pine where lighter-touch harvests (shelterwood harvests or group/patch release) may be useful.
- Certain wildlife may benefit from residual biomass and slash left on site (mushroom-eating small mammals), as well as furbearers that use large hollow logs and cavities as denning and resting sites. Following the voluntary guidelines in Good Forestry in the Granite State (Bennett 2010) sections on cavity trees, dens and snags, and dead and down woody material will develop these habitat conditions over time in managed stands. The proportion of residual biomass that remains following a whole-tree harvest varies widely but has been estimated at as little as 10 percent (Pierce et al. 1993).
- In areas of heavy browsing, leaving some level of residual slash and unlopped tops may help obstruct herbivore activity and reduce the extent and severity of browse damage—especially by deer.
- It is important to be sensitive to the concerns of adjacent landowners about appearances of heavy harvests. Where necessary, make use of uncut buffers and reserve blocks of timber.
Bennett, K. P. editor. 2010. Good Forestry in the Granite State: Recommended Voluntary Forest Management Practices for New Hampshire (second edition). University of New Hampshire Cooperative Extension, Durham, N.H.
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Noel, D.S.; C.W. Martin; C.A. Federer. 1986. Effects of forest clearcutting in New England on stream macroinvertebrates and periphyton. Environmental Management. 10:661-670.
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Roxby, G.E.; T.E. Howard. 2013. Whole-tree harvesting and site productivity: twenty-nine northern hardwood sites in central New Hampshire and western Maine. Forest Ecology and Management. 293:114-121.
Rudnicky, T.C.; M.L. Hunter. 1993. Reversing the fragmentation perspective: effects of clearcut size on bird species in Maine. Ecological Applications. 3: 357-366.
Wilkerson, E.; J.M. Hagan; D. Siegel; A.A. Whitman. 2006. The effectiveness of different buffer widths for protecting headwater stream temperature in Maine. Forest Science. 52: 221-231.
Wilkerson, E.; J.M. Hagan; A.A. Whitman. 2010. The effectiveness of different buffer widths for protecting water quality and macroinvertebrate and periphyton assemblages of headwater streams in Maine, USA. Canadian Journal of Fisheries and Aquatic Sciences. 67:177-190.