Use shelterwood harvesting instead of clearcutting

Supporting evidence from individual studies

1. A replicated, controlled, before-and-after study in 2007–2009 in three hardwood forests in Indiana, USA (Summerville 2011, same study as Summerville 2013) found that timber harvesting method, including shelterwood harvesting, did not affect the number of moth species, but all harvested forest stands had fewer moths than unharvested stands. One year after harvesting, there was no significant difference in the number of moth species between stands subjected to shelterwood harvesting and clearcutting (46 species, data not separated), single-tree harvesting (39 species) or group-selection harvesting (40 species), but all harvested stands had fewer species than unharvested stands (56 species). One year before harvesting, all stands had a similar number of moth species (shelterwood/clearcutting: 96; single-tree: 85; group-selection: 100; unharvested: 90 species). After harvesting, the community composition of shelterwood and unharvested stands in one forest were more similar to an unharvested forest than to two nearby clearcut stands (data presented as model results). In 2008, forest stands (3–5 ha, 150–350 m apart) in three watersheds (500 ha, 10 km apart) were logged. In one watershed, three stands were shelterwood harvested (15% of trees removed), two stands were clearcut (100% of trees removed), and three stands were unharvested (no trees removed). In a second watershed, four stands had random single trees removed, and four stands were harvested by group-selection (80% of trees removed). In the third watershed, all four stands were unharvested. All stands had been clearcut around 60 years earlier. From June–August 2007 and 2009, moths were surveyed every 14 nights (five times/year) from 8pm–7am using a black-light trap placed 2 m above the ground in the centre of each forest stand.

   Study and other actions tested

   Referenced paper

   Summerville K.S. (2011) Managing the forest for more than the trees: Effects of experimental timber harvest on forest Lepidoptera. Ecological Applications, 21, 806-816.

2. A replicated, controlled, before-and-after study in 2007–2011 in two hardwood forests in Indiana, USA (Summerville 2013, same study as Summerville 2011) found that after shelterwood harvesting, the number of moth species recovered faster than after group-selection harvesting or clearcutting. Three years after shelterwood harvesting, the total number of moth species (73 species/stand) and the number of specialist species (23 species/stand) was similar to before harvesting (total: 96; specialist: 23 species/stand). Numbers of species had not recovered following group-selection harvesting (total: after: 52; before: 100; specialist: after: 8; before: 19 species/stand) or clearcutting (total: after: 48; before: 98 species/stand; data for specialists not presented). However, the number of herbaceous-feeding species was higher after group-selection harvesting (10 species/stand) and clearcutting (16 species/stand) than before harvesting (group-selection: 3; clearcutting: 4 species/stand), but remained similar after shelterwood harvesting (after: 6; before: 4 species/stand). In 2008, forest stands (3–5 ha, 350–750 m apart) in two watersheds (500 ha, 10 km apart) were logged. In one watershed, three stands were shelterwood harvested (15% of trees removed), two stands were clearcut (100% of trees removed), and three stands were unharvested. In a second watershed, four stands were harvested by group-selection (80% of trees removed) and four stands were unharvested. All stands had been clearcut around 60 years earlier. From June–August 2007 and 2009–2011, moths were surveyed every 14 nights (five times/year) from 8pm–7am using a black-light trap placed 2 m above the ground in the centre of each forest stand.

   Study and other actions tested

   Referenced paper

   Summerville K.S. (2013) Forest lepidopteran communities are more resilient to shelterwood harvests compared to more intensive logging regimes. Ecological Applications, 23, 1101-1112.

3. A controlled, before-and-after study in 2007–2014 in two hardwood forest blocks in Indiana, USA (Murray et al. 2017) found that shelterwood harvested areas had more macro-moth species than clearcut areas, and a similar number to unharvested forest. One–six years after management, the species richness of macro-moths in shelterwood harvested areas (53–75 species/site) was higher than in clearcut (34–54 species/site) or patch-cut (30–52 species/site) areas, and was similar to thinned (40–68 species/site) or unharvested areas (56–84 species/site). Before harvesting, all areas had similar species richness (shelterwood: 95; clearcut: 96; patch-cut: 99; thinned: 84; unharvested: 90 species/site). After management, the total species richness in the shelterwood and clearcut block was 144–190 species, compared to 122–162 species in the thinned and patch-cut block, whereas before management richness was similar (shelterwood/clearcut: 198; thinned/patch-cut: 203 species; statistical significance not assessed). Two ~100 ha regenerated forest blocks were managed in autumn 2008. In one “even-aged” block, two 4.1-ha areas were shelterwood harvested (non-oak midstory and understory cleared), two 4.1-ha areas were clearcut, and the remaining area was not harvested. In one “uneven-aged” block, two 2.0-ha, two 1.2-ha and four 0.4-ha areas were patch-cut, and the remaining area was thinned by single-tree selection. One block was left unharvested. From May–August 2007 and 2009–2014, macro-moths were sampled on five nights/year (once/fortnight) using 12 W black-light traps. Traps were placed in the centre of 16 patches: three shelterwood, two clearcut and three unharvested sites within the even-age block; four patch-cut and four thinned sites within the uneven-age block. Species represented by fewer than three individuals were excluded.

   Study and other actions tested

   Referenced paper

   Murray B.D., Holland J.D., Summerville K.S., Dunning J.B., Saunders M.R. & Jenkins M.A. (2017) Functional diversity response to hardwood forest management varies across taxa and spatial scales. Ecological Applications, 27, 1064-1081.