Action: Log/remove trees within forests: effects on young trees
- One replicated controlled study in Canada found that logging trees in forests increased the density of young trees. One replicated controlled study in Costa Rica found mixed effects on the density of young trees.
Here logging is defined as the selective removal of trees with the aim of removing tree biomass. This helps to restore natural open woodland by creating gaps and increasing light availability within the forest, which may increase the growth of the remaining vegetation. Interventions where trees are removed to enhance the future condition of a forest and the development of remaining trees are discussed under ‘Thin trees within forests’. Studies comparing the effects of partial logging with clearcutting are discussed in ‘Use partial retention harvesting instead of clearcutting'.
Supporting evidence from individual studies
A replicated, controlled study in 1992-2001 in boreal forest in Ontario, Canada (Bebber et al. 2005) found that structural retention harvest increased tree sapling density. Average sapling density increased from 4,178 to 5,109 saplings/ha in harvested compared with unharvested plots. Harvesting was carried out in 1992. Remaining trees were healthy seed bearers and declining quality trees. Six unharvested control plots and 12 harvested plots, spread over an area of approximately 1,200 ha were monitored during August and September 2001. Plot areas varied from 3 to 104 ha (average 26 ha). Fifty five sample points were placed within control plots and 89 within harvested plots (3–20 points/plot). Tree saplings were recorded inside a 5 m radius ring around plot centre.
A replicated, controlled study in 1997-2002 in tropical rain forest in Costa Rica (Lobo et al. 2007) found that selective logging decreased the density of seedlings and small juvenile trees but increased the number of larger trees. For Caryocar costaricense, the density (individuals/ha) of seedlings (<50 cm tall) (logged: 3.1; unlogged: 4.5) and small juveniles (<2 cm diameter at breast height) (logged: 5.2; unlogged: 8.0) was higher in unlogged plots. In contrast, the density of large juveniles (2-10 cm diameter at breast height) was higher in logged plots (logged: 4.3; unlogged: 2.4). For purpleheart Peltogyne purpurea, the density of seedlings (logged: 208.8; unlogged: 511.2) was higher in unlogged plots, while the density did not differe for small (logged: 2.2; unlogged: 3.1) and large juveniles (logged: 2.6; unlogged: 2.2). Data were collected in 2002 in three logged (selective logging in 1997-1998) and three unlogged plots (100 × 30 m) in each of 11 sites.
- Bebber D., Cole W., Thomas S., Balsillie D. & Duinker P. (2005) Effects of retention harvests on structure of old-growth Pinus strobus L. stands in Ontario. Forest ecology and management, 205, 91-103
- Lobo J., Barrantes G., Castillo M., Quesada R., Maldonado T., Fuchs E.J., Solís S. & Quesada M. (2007) Effects of selective logging on the abundance, regeneration and short-term survival of Caryocar costaricense (Caryocaceae) and Peltogyne purpurea (Caesalpinaceae), two endemic timber species of southern Central America. Forest ecology and management, 245, 88-95