Leave woody debris in forests after logging
Overall effectiveness category Awaiting assessment
Number of studies: 6
Background information and definitions
Retaining woody debris after logging preserves some shelter habitat for reptiles and may mitigate some of the impacts of logging.
For studies discussing leaving deadwood snags in place after logging or wood harvesting, see Leave standing/deadwood snags in forests. For studies discussing adding woody debris back to landscapes, see Habitat restoration and creation – Add woody debris to landscapes.
Supporting evidence from individual studies
A site comparison study in 1978–1982 in pine forests in Florida, USA (Enge & Marion 1986) found that when woody debris was retained following clearcutting prior to replanting, reptile species richness and abundance was higher than when ground cover was cleared and burned prior to replanting. Three years after woody debris was retained prior to replanting, reptile species richness and abundance were higher (richness: 13 species/trapping array, abundance: 41 individuals/array) than after ground cover was cleared and burned (richness: 9, abundance: 19) and similar to uncut forest (richness: 15, abundance: 52). Overall burrow and refugia-dwelling reptiles and amphibians were more abundant in areas where woody debris was retained compared to where ground cover was cleared and burned or in uncut forest (see paper for individual species abundances). Two of three sites (49–140 ha) were clearcut in 1978 and then managed by retaining woody debris cover (in 1978: 59% harvested by chainsaw, January–August 1979: roller chopped twice) or clearing and burning cover (1978: 74% harvested by feller-buncher, January–August 1979: stump removal, burned, harrowed) prior to replanting in September–November 1979. Reptiles were sampled weekly from August 1981 to October 1982 using four drift fence arrays (four 7.5 x 50 cm galvanised flashing fences in a plus-shape with three aluminium window screen funnel traps on each arm) at all three sites.Study and other actions tested
A replicated, randomized, controlled study in 1997–1999 in forest and wetlands in South Carolina, USA (Russell et al. 2002) found that overall abundance and richness of reptiles immigrating to wetlands were similar after clearcutting with cut debris left in place or after clearcutting with replanting compared to before management. After six and 18 months, overall richness and abundance of immigrating reptiles were statistically similar between clearcutting with debris left in place (average change in richness: 45–66% decline, abundance: 54–79% decline), clearcutting with replanting (27–59% decline, 43–70% decline) and no harvesting (28–72% decline, 51–77% decline) compared to before management was carried out. See original paper for details of groups of and individual species changes in immigration compared to before management. Pine Pinus spalustris plantations (<10 ha each) surrounding five wetlands (0.4–1.1 ha) were divided into three and managed in June 1998 by: clearcutting with residual woody debris/slash left in place, clearcutting with replanting (including mechanical site preparation prior to planting), or no harvesting. Reptile movements from the adjacent wetlands were monitored by enclosing each wetland with a drift fence, with pairs of pitfall traps placed every 10 m along the fence. Pitfalls were checked daily in June–December 1997 (pre-treatment), 1998 (6 months post-treatment) and 1999 (18 months post-treatment). Captured individuals were individually marked using toe clipping, PIT tags or shell notching.Study and other actions tested
A replicated, randomized, controlled study in 1998–2005 of pine stands in South Carolina, USA (Owens et al. 2008, same experimental set-up as Davis et al. 2010) found that leaving coarse woody debris in place had no effect on reptile abundance, species richness and diversity compared to removing it. In two trials, removing all downed and standing woody debris did not change reptile richness (debris removed: 5–7 species), diversity (10–17, Shannon-Weiner index) and abundance (0.2–0.5 individuals/plot/night) compared to not manipulating woody debris (richness: 7, diversity: 13–17, abundance: 0.3–0.4). The two treatments were randomly assigned to 9 ha plots within three forest blocks in 1996–2001 and 2002–2005: all woody debris removal or no manipulation. Five drift-fence arrays with pitfall traps/plot were used for sampling in 1998–2005.Study and other actions tested
A replicated, randomized, controlled study in 2004–2006 in pine forests in South Carolina, USA (Todd & Andrews 2008) found that snake abundance was similar in clearcut forest with woody debris left in place compared to when debris was removed, but lower in clearcut compared to thinned forest. The number of snakes captured was similar after clearcutting and leaving coarse woody debris in place (102 individuals) or removing coarse woody debris (80 individuals), but lower than after thinning (180 individuals). Numbers of snakes captured in unharvested plots was 137. Four circular forest sites were divided into four plots and each plot was randomly assigned one of four treatments: clearcut with coarse woody debris retained, clearcut with coarse woody debris removed, 85% thinned and unharvested for >30 years. Logging was from February to April 2004. Reptiles were sampled using drift fences with pitfall traps. Traps were checked every 1–2 days from April 2004 to July 2006 except for August.Study and other actions tested
A replicated, randomized, controlled study in 1996–2008 in a loblolly pine Pinus taeda forest in South Carolina, USA (Davis et al. 2010, same experimental set-up as Owens et al. 2008) found that leaving downed coarse woody debris had no effect on lizard or snake abundance, species richness or diversity compared to removing debris. After retaining woody debris, snake abundance, richness and diversity were similar (abundance: 0.04 individuals/m drift fence, richness: 0.04 species/m drift fence, diversity: 0.01 Shannon-Wiener Index) compared to when debris was removed (abundance: 0.07, richness: 0.04, diversity: 0.01) and also similar to when debris was added (abundance: 0.03, richness: 0.02, diversity: 0.003). For lizards there was also no difference between retaining (abundance: 0.01, richness: 0.07, diversity: 0.02), removing (abundance: 0.15, richness: 0.07, diversity: 0.02) or adding debris (abundance: 0.15, richness: 0.07, diversity: 0.02). Nine ha plots in three pine stands (approximately 45 years old, three plots/stand) were managed by: retaining woody debris (initiated 1996, 13 m3/ha woody debris); removing all downed woody debris ≥10 cm diameter and ≥60 cm in length by hand (initiated 1996, to 0.24 m3/ha in 2006); or increasing volume of downed woody debris five-fold by felling trees (initiated 2001, to 59 m3/ha in 2007). All plots were prescribed burned in 2004. Reptiles were sampled for 14 days/plot in each of seven seasons (January 2007–August 2008) using drift fences with pitfall traps.Study and other actions tested
A replicated, randomized, controlled study in 2010–2014 in commercial pine forests in North Carolina and Georgia, USA (Fritts et al. 2016) found that retaining woody debris after clearcutting did not affect reptile species richness, or overall reptile and amphibian species diversity. Over 3–4 years after clearcutting, reptile species richness and overall reptile and amphibian species diversity were similar when 100% of woody debris was retained, 15–30% of wood debris was retained, or all debris was removed (results reported as statistical model outputs, see original paper for details). Eight replicate sites in three locations (one in North Carolina, two in Georgia) of intensively managed loblolly pine Pinus taeda plantations (64–70 ha/site, 25–35 years old) were clearcut in autumn 2010–summer 2011 and six 11–12 ha plots/site were managed by retaining 100% of woody debris; retaining 30% of woody debris in large piles; retaining 30% of woody debris evenly distributed; retaining 15% of woody debris in large piles; retaining 15% of woody debris evenly distributed; or by removing all woody debris (following traditional practice). Sites were replanted and treated with herbicide in 2011–2012. Reptiles and amphibians were surveyed in April–August 2011–2014 in North Carolina and 2011–2013 in Georgia using three drift fence and funnel trap arrays/plot. Three–eight trapping periods were carried out/year (2011: 10 consecutive days; 2012–2014: five consecutive days).Study and other actions tested