Action: Use shelterwood harvesting
Key messagesRead our guidance on Key messages before continuing
- Six of seven studies (including five replicated, controlled studies) in Australia, Iran, Nepal and the USA found that shelterwood harvesting increased abundance, species richness and diversity of understory plants, as well as the growth and survival rate of young trees. One study found shelterwood harvesting decreased plant species richness and abundance. One study found no effect of shelterwood harvest on tree abundance.
- One replicated, controlled study in Canada found no effect of shelterwood harvest on red oak acorn production.
Shelterwood harvesting is a management technique designed to obtain even-aged forests. It involves harvesting trees in a series of partial cuts, with trees removed uniformly over the plot. This allows new seedlings to grow from the seeds of older trees. This can help to maintain distinctive forest species and increase forest structural diversity.
Supporting evidence from individual studies
A controlled study in 1993-1995 in subtropical moist forest in Nepal (Rautiainen & Suoheimo 1997) found that shelterwood harvest treatments increased the growth rate of the dominant shala tree Shorea robusta seedlings. Height growth was higher in clearcut than other treatment plots (unharvested: 85 cm; 75 trees remaining: 90 cm; 25 trees remaining: 99 cm; clearcut: 127 cm). Diameter growth was higher in clearcut (24 mm) than 25 (17 mm) and 75 trees remaining plots (16 mm), and the lowest in unharvested plots (6 mm)Numbers of shala tree seedlings was similar between treatments (unharvested: 89,292; 75 trees: 73,542; 25 trees: 91,125; clearcut: 81,000). Four treatment plots (1 ha) were established in 1993: unharvested, and 25 trees, 75 trees and clearcut (shelterwood harvest leaving 75, 25 and no trees in the plot, respectively). Growth rate of the 2,000 dominant shala tree seedlings in each plot was calculated for the second growing season after treatments. Numbers of seedlings was determined eight months after treatments.
A replicated, controlled study in 1977-1997 in temperate mixed coniferous forest in California USA (Battles et al. 2001) found that shelterwood harvest increased understory species richness. Numbers of species/1.13 ha was higher in shelterwood (80) than in unharvested plots (48). The study area was divided in sections of 8–80 ha that were assigned to shelterwood harvest (approximately 40 seed-trees/ha were left) and unharvested (since early 1990s) treatments. Understory vegetation was monitored in 30 m radius plots within the section treated annually since 1977.
A site comparison study in 2000 in a Mediterranean jarrah forest in Western Australia (Burrows, Ward & Cranfield 2002) found that shelterwood harvest decreased plant species richness and abundance. The number of native plant individuals/m2 (shelterwood: 29; unharvested: 39) and individuals/30 m2 (shelterwood: 869; unharvested: 1,172), and the number of native plant species/m2 (shelterwood: 9.6; unharvested: 11.9) were lower in shelterwood than unharvested plots. The number of species/30 m2 was similar between treatments (shelterwood: 55; unharvested: 57). Data was collected in five lines of 30 quadrats (1 × 1 m) in shelterwood (retaining basal area of 13 m2/ha, applied in 1995) and unharvested treatments located in an 11,000 ha study area.
A replicated, controlled study in 1993-1997 in temperate mixed forest in Ontario, Canada (Bellocq et al. 2005) found no effect of shelterwood harvest on the acorn crop of red oak Quercus rubra. Acorn production (unharvested: 29,577; shelterwood: 28,697/plot) and the percentage of acorns damaged by insects (shelterwood: 44%; unharvested: 47%) were similar between treatments. Five shelterwood (trees cut to 50% crown cover) and five unharvested plots (60 m × 60 m) were established in 1993-1994. Acorns were sampled using one trap (1 × 1 m) per 120 m2 of crown cover (total of 86 traps) in August-November 1997.
A replicated, controlled study in 1994-2000 in mixed hardwood forest in North Carolina USA (Elliott & Knoepp 2005) found that shelterwood harvest increased the density and the diversity of plants. The density (individuals/ha) of trees (shelterwood: 1,009-1,094; uncut: 771), density of shrubs (shelterwood: 38,269-49,117; uncut: 21,789), number of shrub species/plot (shelterwood: 10; uncut: 4) and diversity (Shannon index) of herbaceous plants (shelterwood: 2.2-2.4; uncut: 1.8) were higher in shelterwood harvest treatments. In 1994, eight sites (4.0-6.6 ha) were each assigned to one of three treatments: three sites of two shelterwood treatments (5 m2/ha and 9 m2/ha residual basal area), and two uncut sites. Monitoring was in 2000 in four plots (20 × 40 m) in each treatment site.
A replicated, controlled study in 2000-2001 in temperate broadleaf forest in Tennessee, USA (Jackson et al. 2006) found that shelterwood harvest increased herbaceous species diversity. Diversity of herbaceous species (shelterwood: 4.2; unharvested: 3.1) was higher in shelterwood, while that of woody plants (shelterwood: 2.7-2.9; unharvested: 2.3-2.8) was similar between treatments. In July 2001, shelterwood (leaving high-quality stems, retaining 11.5 m2/ha basal area) and unharvested treatments were applied each to two plots (0.8 ha) in each of four sites (total of 16 plots). Data was collected after treatment in summer 2001. Simpson's index was calculated for 3.6 m radius circular subplot in each plot.
A replicated, controlled study in 1986-2005 in Hyrcanian forest in Iran (Pourmajidian et al. 2010) found that shelterwood harvest increased the abundance of some herbaceous species, but not of trees. The frequency of four out of 17 herbaceous species was higher in shelterwood (16-27%) than unharvested plots (1-17%). The frequency of the other 13 species was similar between treatments (shelterwood: 1-20%; unharvested: 0-12%). Density (individuals/ha) of the dominant tree species oriental beech Fagus orientalis (shelterwood: 100; unharvested: 103), as well as of another six tree species (shelterwood: 0-8; unharvested: 0-9) was similar between treatments. Trees density was measured in 60 unharvested and 60 shelterwood (20-25% intensity in 1986 and 1991) treatment plots (100 m2). Herbaceous species were monitored in 1 m2 subplots within the plots. Data was collected in 2005.
A replicated, controlled study in 2001-2009 in temperate mixed oak forest in Pennsylvania USA (Brose 2011) found that shelterwood harvest treatments increased the survival of oak Quercus spp. seedlings. The number of surviving black oak Quercus velutina and northern red oak Q. rubra seedlings/32 m2 plot was highest in complete harvest and large-scale harvest plots (180-220), lower in preparatory cut plots (100-150) and the lowest in uncut plots (25-50). The number of surviving chestnut oak Quercus montana seedlings was higher in the three cutting treatments (120-180) than in uncut plots (25). The number of surviving white oak Quercus alba seedlings was the highest in complete harvest plots (200), lower in large-scale harvest plots(150) and the lowest in preparatory cut and uncut plots (10-50). Four treatments: uncut, preparatory cut (harvest of intermediate trees), large-scale harvest and complete harvest were replicated at each of five sites. Monitoring was in four 8 × 4 m plots in each treatment, each planted with 400 seedling of one of the four oak species.
- Rautiainen O. & Suoheimo J. (1997) Natural regeneration potential and early development of Shorea robusta Gaertn. f. forest after regeneration felling in the Bhabar-Terai zone in Nepal. Forest Ecology and Management, 92, 243-251
- Battles J.J., Shlisky A.J., Barrett R.H., Heald R.C. & Allen-Diaz B.H. (2001) The effects of forest management on plant species diversity in a Sierran conifer forest. Forest ecology and management, 146, 211-222
- Burrows N., Ward B. & Cranfield R. (2002) Short-term impacts of logging on understorey vegetation in a jarrah forest. Australian Forestry, 65, 47-58
- Bellocq M., Jones C., Dey D. & Turgeon J. (2005) Does the shelterwood method to regenerate oak forests affect acorn production and predation? Forest ecology and management, 205, 311-323
- Elliott K.J. & Knoepp J.D. (2005) The effects of three regeneration harvest methods on plant diversity and soil characteristics in the southern Appalachians. Forest Ecology and Management, 211, 296-317
- Jackson S.W., Harper C.A., Buckley D.S. & Miller B.F. (2006) Short-term effects of silvicultural treatments on microsite heterogeneity and plant diversity in mature Tennessee oak-hickory forests. Northern Journal of Applied Forestry, 23, 197-203
- Pourmajidian M.R., Jalilvand H., Fallah A., Hosseini S.A., Parsakhoo A., Vosoughian A. & Rahmani A. (2010) Effect of shelterwood cutting method on forest regeneration and stand structure in a Hyrcanian forest ecosystem. Journal of Forestry Research, 21, 265-272
- Brose P.H. (2011) A comparison of the effects of different shelterwood harvest methods on the survival and growth of acorn-origin oak seedlings. Canadian journal of forest research, 41, 2359-2374