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Providing evidence to improve practice

Action: Use clearcutting to increase understory diversity Forest Conservation

Key messages

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Supporting evidence from individual studies

1 

A replicated, controlled, before-and-after study in 1992-1993 in bottomland hardwood forest in Texas, USA (Messina et al. 1997) found that clearcutting increased tree species diversity. Shannon's index of diversity for trees <4 cm DBH increased in clearcut plots (before: 2.21; after: 2.33), but remained similar in partial-cut (before: 2.30; after: 2.33) and control plots (before: 1.95; after: 1.98). In 1992, three treatment plots (8.1 ha): clearcut (all woody vegetation cut), partial-cut (50% of basal area cut) and control (uncut) were replicated in three blocks. Data were collected in 1993 in nine subplots (40 m2) in each plot.

 

2 

A replicated, randomized, controlled study in 1993-1995 in temperate broadleaf forest in Indiana, USA (Jenkins & Parker 1998) found that cutting treatments increased species richness of tree saplings but not of small seedlings, and had mixed effects on mature tree species richness. Species richness (in 100 m2 plot) of saplings (>1 m tall, <3 cm DBH) was higher in recent clearcut (8.7-9.1) and group cut (7.8-8.5) than in uncut plots (2.3-3.3), but similar to uncut plots for old clearcut ((4.9-6.1), old group cut (3.0-5.0), recent single tree cut (4.7-5.6) and old single tree cut plots (2.1-2.7). Species richness of seedlings (<1 m tall) was similar between treatments (7.2-11.6).  Species richness of mature trees (>3 cm DBH) was higher in old clearcut plots (10.4-10.7) and lower in single tree cut plots (recent single tree: 2.7-3.2; old single tree: 2.7-2.8) compared with uncut plots (6.8-7.3), but similar to uncut plots for recent clearcut (7.6-9.6), recent group cut (5.9-6.5) and old group cut (6.0-6.6). Species richness was calculated in a 100 m2 plot in each of 37 clearcutting, 45 group selection (cutting in groups, 0.1-1.6 ha) and 44 single tree selection cuts (cutting single trees, 0.005-0.012 h), recent (7-15 years) and old (16-27 years) treatment units and in 24 uncut plots (uncut >80 years).

 

3 

A replicated, randomized, controlled study in 1993-1995 in temperate broadleaf forest in Indiana, USA (Jenkins & Parker 2000) found that cutting treatments increased species richness but not the diversity of herbaceous species and low plants. Species richness (in 4 m2 quadrat) was higher in clearcut (43) and group cut (47) compared to single tree cut (36) and uncut plots (34). Diversity (Shannon's index) was similar in all treatments (2.6-2.8). One plot (100 m2) was established in each of 12 clearcut, 16 group selection (cutting in groups, 0.1-1.6 ha), 17 single tree selection cuts (cutting single trees, 0.005-0.012 h) and 12 uncut (>80 years) treatment plots. Data were collected in four quadrats (4 m2) in each plot

 

4 

A replicated, randomized, controlled study in 1985-1997 in tropical forest in Pará State, Brazil (Parrotta, Francis & Knowles 2004) found that clearcuttng decreased species richness, density and size of trees, but not species richness, density and size of vines, herbaceous species and grasses. Species richness of trees (>15 cm diameter at breast height) was higher in uncut (20/plot) and low intensity cuts (20) than in clearcut and moderate intensity cuts plots (clearcutting: 7/plot; moderate-intensity: 12). Numbers of trees/ha was lower in moderate intensity cut plots (164) than in the other treatments (uncut: 323; low intensity: 339; clearcut: 296). Trees basal area (m2/ha) was higher in low (16) and moderate intensity cuts (17) than in clearcuts (9) and highest in uncut plots (uncut: 25). Density of vines (uncut: 17,468; low intensity: 8,758; moderate intensity: 11,174; clearcuts: 9,268), herbaceous species (uncut: 1,210; low intensity: 1,131; moderate intensity: 1,401; clearcuts: 1,417) and grasses (uncut: 334; low intensity: 223; moderate intensity: 270; clearcuts: 6,362), and species richness/plot of vines (uncut: 13; low intensity: 13; moderate intensity: 12; clearcuts: 12), herbaceous species (uncut: 3; low intensity: 2; moderate intensity 2; clearcuts: 3) and grasses (<1 in all treatments) were similar between treatments.  Data were collected in 1996-1997 in four treatments (20 × 70 m2): uncut, low intensity cuts (trees ≥45 cm diameter at breast height removed), moderate intensity cuts (trees ≤20 and ≥60 cm removed), and clearcutting, replicated randomly in four blocks in 1985.

 

5 

A replicated, randomized, controlled study in 1998-2001 in boreal forest in Quebec, Canada (Bourgeois, Messier & Brais 2004) found that clearcutting increased the density of new mountain maple Acer spicatum stems and the relative regrowth rates of mountain maple and balsam fir Abies balsamea compared with thinning. Density of new mountain maple stems was higher in clearcut (13 stems/m2), compared to 33% cut (3), 66% cut (3) and uncut plots (5). Mountain maple relative trunk growth (clearcut: 240%; 66% cut: 130%: 33% cut: 140%; uncut: 130%) and mortality rate (clearcut: 35%; 66% cut: 20%; 33% cut: 27%; uncut: 30%) were similar between treatments. Balsam fir relative height growth ratio for stems <1 m differed between the four different treatments (clearcut: 25%: 66% cut: 15%: 33% cut: 9%; uncut: 4%), while those of stems 1-3 m were similar between treatments (17%, 17%, 9% and 7% respectively). There were three replicates (1-2.5 ha) of four treatments: clearcutting, 66% cut, 33% cut and no harvest (100%, 61%, 33% and 0% of basal area removed respectively).  Plots were established in winter 1998-1999. Monitoring was in 1 m2 quadrats (120 for mountain maple, 226 for balsam fir).

6 

A replicated, randomized, controlled study in 1995-1999 in temperate mixed forest in Ontario, Canada (MacDonald, Cherry & Thompson 2004) found no effect of clearcutting on the size of trees and shrubs. There was no difference between treatments for: height of <4.0 m tall (71-140 cm), and DBH of >4 m tall and 1-10 cm DBH (5.7-6.2 cm) coniferous trees, height (59-177 cm) and density (5,417-12,292 stems/ha) of hardwood regenerations, and height (109-168 cm) and ground cover (33-51%) of shrubs. Data was collected in 1999 in four treatment plots (100 × 100 m): 0% (clearcut), 36%, 68%, and 100% (uncut) of basal area removed, established in 1995 in each of four blocks.

 

7 

A replicated, randomized, controlled study in 1998–2000 in temperate coniferous forest in South Dakota, USA (Wienk, Sieg & McPherson 2004) found that clearcutting increased tree species richness. Tree species richness/plot was higher in clearcut (15) than partial-cut plots (8) and the lowest in uncut plots (3). Data were collected in July 2000 in six uncut, six partial-cut (retaining 12 m2/ha basal area) and six clearcut plots (45 × 45 m) established in winter 1998-1999. Three plots of each treatment were prescribed burned in May 1999.

 

8 

A site comparison study in temperate broadleaf forest in Belgium (Godefroid, Rucquoij & Koedam 2005) found that clearcutting had mixed effects on forest herbaceous species. Woodland germander Teucrium scorodonia, pill sedge Carex pilulifera, and common bracken Pteridium aquilinum were more frequent in clearcuts (30%, 25% and 20%) than in uncut forest areas (9%, 15% and 7%). Broad buckler-fern Dryopteris dilatata, remote sedge Carex remota, enchanter’s-nightshade Circaea lutetiana, hairy wood-rush Luzula pilosa and greater wood-rush L. sylvatica were more frequent in uncut forest areas (62%, 60% 43%, 12% and 10%) than in clearcuts (46%, 32% 3%, 4% and 3%). Frequencies of wavy hair-grass Deschampsia flexuosa, common wood sorrel Oxalis acetosella, tufted hair-grass D. cespitosa and wood anemone Anomone nemorosa were similar (approximately 30%, 20%, 20% and 3% respectively). Relative cover of broad buckler-fern (46% vs 13%), common bracken (4% vs 19%), enchanter’s-nightshade (15% vs 0%), Woodland germander (10% vs 3%), hairy wood-rush (8% vs 1%) and common wood sorrel (5% vs 2%) was higher in uncut forest than in clearcuts while relative cover the other species was similar. Forest herbaceous species were sampled using total of 82 quadrats (4 m2) in four clearcut sites (0.5 – 2 ha) ages 6 – 13 years, and 219 grid cells (50 × 50 m) in uncut forest areas (surrounding the sites).

 

9 

A replicated, randomized, controlled study in 2001-2002 in subtropical Araucaria forest in Brazil (Zanini & Ganade 2005) found that clearcutting and complete vegetation removal increased species richness and abundance of new seedlings. Species richness/m2 (clearcut: 0.7-2.0; uncut: 0.2-0.6) and abundance (clearcut: 0.8-2.6; uncut: 0.2-0.7) were higher in removal than uncut plots. Data were collected in 2002 in two removal (all plants and organic material removed in 2001) and two uncut plots (3 × 3 m) in each of 10 blocks randomly located inside a 2 ha area.

 

10 

A replicated, controlled, before-and-after study in 1994-2000 in temperate broadleaf forest in Missouri, USA (Zenner et al. 2006) found that cutting increased plant species richness and ground vegetation cover. Change in plant species richness was the greatest in clearcut, higher in group than single tree selection plots, and the lowest (and negative) in unthinned plots (clearcut: 21; group-selection: 12; single-tree-selection: 3; thinning: 7; unthinned: -3). Change in ground vegetation cover was the greatest in clearcut and the lowest in unthinned plots (clearcut: 43%; group selection: 17%; single tree selection: 10%; thinning: 9%; unthinned: 0%). Data were collected in 1994-1995 (before treatment) and in 1999-2000 (after treatment) in 45 group selection, 79 single tree selection and 36 thinning plots (25% trees reduction in all), and in 24 clearcut and 236 control plots (0.2 ha). Treatments were applied in 1996-1997.

 

11 

A replicated, controlled study in 1998-2001 in boreal forest in Alberta, Canada (Macdonald & Fenniak 2007) found that clearcutting decreased tree density, basal area and cover as well as herbaceous cover and species richness. Tree density (individuals/ha) (uncut: 568-1,069; thinned: 242-700; clearcutting: 26-52), basal area (m2/ha) (uncut: 87-140; thinned: 39-105; clearcutting: 6-12) and canopy cover (uncut: 44-49%; thinned: 38-78%; clearcutting: 9-13%) were higher in uncut than clearcut plots. Herbaceous cover (uncut: 72-78%; thinned: 26-74%; clearcutting: 34-36%) and number of species/1 m2 (uncut: 9-10; thinned: 7-9; clearcutting: 6) were higher in uncut than clearcut plots. Trees were monitored in 12 uncut, 18 thinned (20-75% retention) and nine clearcut (2% retention) plots (50 m2). Herbaceous species were monitored in 1 × 1 m subplot within each plot. Treatments were applied in 1998-1999, monitoring was two years after treatment.

 

12 

A replicated, controlled study in 1995-2005 in boreal forest in Ontario, Canada (Man et al. 2008) found that clearcutting increased the density and height of conifer regenerations and decreased the density of hardwood regenerations. Conifer regeneration density (stems/ha) was higher in clearcut (8,000) than in partial-cut and uncut plots (2,000-3,000) Height was higher in clearcut and partial-cut plots (270-300 cm) than uncut plots (140 cm). Hardwood regeneration density was lower in clearcut (1,500) than partial-cut and uncut plots (4,500-5,000). Height was similar in all treatments (110-180 cm). Four plots (100 × 100 m): one uncut, two partial-cut and one clearcut (0%, 40% and 100% of merchantable trees basal-area removed) were replicated in four blocks in January-February 1995. Data were collected in 2005 in 12 subplots (2 × 2 m) within each plot.

 

13 

A replicated, controlled, study in 2005-2007 in Mediterranean-type shrubland in Israel (Agra & Ne'eman 2009) found that clearcutting increased herbaceous species richness under tree canopies. Numbers of herbaceous species/0.1 ha plot was higher in clearcut (81) than in uncut plots (18). Ten uncut and ten clearcut plots (0.1 ha) were established in December 2005. In April 2007, herbaceous species were monitored in uncut and in clearcut plots in areas that were covered with tree canopy before treatment.

 

14 

A replicated, randomized, controlled study in 1998-2006 in boreal mixed wood forest in Alberta Canada (Craig & Macdonald 2009) found that clearcutting and high thinning intensity increased the cover of understory vegetation, particularly of grasses. The average percentage cover of all species under the canopy was 67% in clearcut and high thinning intensity plots (0-10% retention) and 55% in the three low thinning intensities and uncut plots (20-100% retention). The average percentage cover of grasses was 14% in clearcut and high thinning intensity plots and 4% in the three low thinning intensities and uncut plots. Species richness was unaffected by retention level. In winter 1998-1999, six 10 ha compartments within each of three blocks (∼2 km2) were randomly assigned to six harvesting treatments: clearcutting (0% retention), 10% retention, 20% retention, 50% retention, 75% retention and uncut (100% retention). Sampling was conducted in summer 2006 in twenty 1×1 m plots in each of the 18 compartments.

 

15 

A site comparison study in 2004 in tropical moist lowland forest in Hainan Island, China (Ding & Zang 2009) found that clearcutting increased species richness and abundance of lianas. Species richness(species/ha) was 52 in the clearcut, 50 in the selective cut and 42 in the uncut site. Abundance of lianas (stems/ha) was 606 in the clearcut, 727 in the selective cut and 261 in the uncut site. Average diameter at breast height of liana stems was 2.7 cm in the clearcut, 3.1 cm in the selective cut and 4.5 cm in the uncut site. In 2004, a 1 ha plot was established in each of: uncut (since 1964) clearcut and selective cut (since 1964) forest sites. Each plot was divided to 100 quadrants (10 × 10 m). Liana stems were monitored in 2004.

 

16 

A replicated, randomized, controlled study in 2003-2006 in temperate coniferous forest in Spain (González-Alday, Martínez-Ruiz & Bravo 2009) found that clearcutting reduced the number of maritime pine Pinus pinaster seedlings, and increased annual plant cover and the number of herbaceous plant species. The number of maritime pine seedlings/plot was highest in uncut plots (66). It was higher in closed canopy (16) than in clearcut plots (1), and similar to both in open canopy plots (8). The number of annual species/plot was the highest in clearcut plots (41). It was higher in open canopy (31) than in uncut plots (24) and similar to both in closed canopy plots (29). The number of perennial herbaceous species/plot was highest in clearcut plots (17), and similar in open (11) and closed canopy (10) and uncut plots (9). Annual plant cover was lowest in uncut plots (21%), and similar in closed (37%) and open canopy (40%) and clearcut plots (42%). Perennial herbaceous species cover was higher in clearcut (16%) than open canopy plots (7%), and similar to both in uncut (11%) and closed canopy plots (10%). Three replicates (70 × 70 m) of each of four treatments: uncut; closed canopy (25% of basal area removed); open canopy (50% of basal area removed); clearcut (all trees removed) were established in 2003. Sampling was in 2006.

 

17 

A replicated, controlled study in 2003-2007 in temperate coniferous forest in Germany (Heinrichs & Schmidt 2009) found that clearcutting increased species richness and cover of understory vegetation. Species richness (species/100 m2) of herbaceous species (clearcut: 26-41; selection cutting: 26-32; control: 20-25) and cover of shrubs (clearcut: 14-21%; selection cutting: 13-20%; control: 0-3%) was similar between cutting treatments, but lower in control plots. Species richness of shrubs was higher in clearcut (8-9) than selection cutting plots (4-6) and lowest in control plots (2). Cover of herbaceous species was higher in clearcut (46-64%) than in control plots (18-48%) and similar to both those treatments in selection cutting plots (25-59%). In 2003, two plots (1 ha) of each treatment: clearcut (removing all trees), selection cutting (removing trees >45 cm DBH) and control (untreated) were established in each of two sites. Data were collected in 2007 in 20 subplots (100 m2) in each plot.

 

18 

A replicated, controlled study in 1993-2007 in boreal forest in Ontario, Canada (Li, Dang & Ambebe 2009) found no effect of clearcutting on tree stem density. Density was similar between treatments (clearcut: ~25,000 stems/ha; uncut: 23,560 stems/ha). Two replicates of clearcut (all merchantable timber removed) and uncut treatment sites were established in 1993. Data were collected in 2007 in ten 50 m2 plots in each treatment site.

 

19 

A replicated, randomized, controlled study in 1993-2007 in boreal forest in Ontario, Canada (Man, Rice & MacDonald 2009) found no effect of clearcutting on the density of new tree regenerations. Density (stems/ha) of hardwood and conifer regenerations was similar in all treatments (hardwood: ~4,000; conifer: ~1,500). In 1993-1994, four treatments: control (uncut), 50% partial cut, 50% partial cut with removal of residuals after 3 years, and clearcut were replicated in six blocks (112 × 56 m). Data were collected in 1998-2007.

 

20 

A replicated, randomized, controlled study in 2000-2002 in boreal forest in Finland (Manninen et al. 2009) found that clearcutting decreased total plant biomass and the relative biomass of evergreen shrubs, but not deciduous shrubs, grasses or herbaceous species. Total above ground biomass (clearcut: 12-20 g/m2; control: 140-190 g/m2) and relative biomass of evergreen shrubs (clearcut: 20-25%; control: 30-40%) were lower in clearcut. However, relative biomass of deciduous shrubs (53-67%) grasses (1-17%) and herbaceous species (1-7%) was similar between treatments. Data were collected in 2002 in 32 pairs of 0.5 × 0.5 m clearcut plots (biomass above the moss layer clipped each year 2002-2002) and 0.25 × 0.25 m control plots in each of two sites.

 

21 

A replicated, paired sites study in 2003 in tropical forest in Brazil (Ribeiro, Bruna & Mantovani 2010 found that clearcutting decreased herbaceous density. Herbaceous density (individuals/8 m2 subplot) was lower in clearcut (3) than uncut (17) plots. Data were collected in 2003 in 25 subplots (4 × 2 m) within each plot (250 × 100 m) of three uncut (primary forest) and clearcut (secondary forest, cut in 1980-1984) pairs.

 

22 

A before-and-after trial in 1992-2003 in boreal forest in Quebec, Canada (Grandpré et al. 2011) found that clearcutting increased understory species richness, diversity and cover. Numbers of species/1 m2 plot increased in clearcut plots (before: 5-8; after: 9-13) and remained similar in uncut plots (before: 5-10; after: 6-12). Species diversity (Shannon's index) increased in clearcut plots (before: 0.7-1.2; after: 1.4-1.7) and remained similar in uncut plots (before: 0.7-1.3; after: 0.8-1.5). Cover increased in clearcut (before: 70-90%; after: 140-160%), but not uncut plots (before: 90-100%; after: 90-120%). In 1992, clearcut (all trees cut and removed) and uncut treatments (100 m2) were replicated in three blocks (>625 m2) at each of two sites. Data were collected before (1992) and after treatments (2003) in 5-12 plots (1 m2) in each treatment.

 

23 

A replicated, controlled study in 2006 in temperate woodland in south-eastern Australia (Dorrough et al. 2012) found no effect of clearcutting on native plant species richness. Numbers of native plant species/plot was similar between treatments (clearcut: 15; control: 19). Monitoring was in two pairs of clearcut and adjacent control plots (1 ha) in each of 12 sites (a total of 48 plots).

 

24 

A before and after study in 1995-2003 in subtropical forest in Okinawa Island, Japan (Wu et al. 2013) found no effect of clearcutting on tree species richness and diversity. Species richness/plot (before: 33; after: 50) and Shannon's diversity (before: 4.0; after: 4.8) in cut plots were higher after treatment. However, species richness (before: 24; after: 45) and diversity (before: 3.4; after: 4.5) were higher in uncut plots. Data were collected before (January 1995) and after treatment (2003) in five clearcut (in February 1995) and five uncut plots (10 × 10 m) established within a 4,000 m2 forest section.

 

Referenced papers

Please cite as:

Agra H., Schowanek S., Carmel Y., Smith R.K. & Ne’eman G. (2019) Forest Conservation. Pages 331-347 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.