Canopy removal and residual stand damage during controlled selective logging in lowland swamp forest of northeast Costa Rica

Abstract

Sustainable timber extraction through selective logging has been proposed as a method of forest management that can help curtail the rate of tropical deforestation. This paper reports canopy removal and residual stand damage estimates for a controlled selective logging operation in lowland swamp forest of northeast Costa Rica. The logging procedure only harvested Carapa nicaraguensis (Meliaceae) trees of at least 70 cm dbh (diameter at 1.4 m or above buttresses). Logging removed 6.3 trees ha −1 (SD = 4.2) from 28 ha, and 45.8 m 3 ha −1 from a 7 ha subsample. Canopy cover was 91% (SD = 4.5) in undisturbed forest, and 73% (SD = 12.4) in logged forest. Post-logging canopy cover was negatively correlated with the number of trees extracted ha −1. Prior to logging, 65% of total gap area was contained in gaps less than 250 m 2. After logging, gaps of over 500 m 2 represented 78% of total gap area. Stand basal area in 7 ha of inventoried forest was reduced by 18.3%, and 17.6% of residual stems were damaged or killed. Wet soil conditions required the use of 5.3% of residual stems to construct corduroy skid trails. Thus, 30% of all residual stem damage resulted from soil conservation efforts. Stem damage estimates were compared with those reported from uncontrolled tropical logging operations. Although absolute levels of residual damage during controlled logging were quite low, there was no conclusive evidence that total residual damage was relatively lower than intensity-adjusted estimates of those other operations. In contrast, canopy removal during logging was lower than that in two other neotropical studies. Both residual damage and canopy removal can be decreased further by incorporating stricter felling guidelines; measures to reduce necessary levels of skid trail fortification would also decrease residual damage. The results are discussed in the broad context of tropical forest management. A conservative approach to tropical forestry increases the possibility of sustainable extraction of the resource.