CANOPY REMOVAL AND RESIDUAL STAND DAMAGE DURING CONTROLLED SELECTIVE LOGGING IN LOWLAND SWAMP FOREST OF NORTHEAST COSTA-RICA

Sustainable timber extraction through selective logging has been propo sed as a method of forest management that can help curtail the rate of tropical deforestation. This paper reports canopy removal and residua l 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 tr ees ha(-1) (SD = 4.2) from 28 ha, and 45.8 m(3) ha(-1) from a 7 ha sub sample. Canopy cover was 91% (SD = 4.5) in undisturbed forest, and 73% (SD = 12.4) in logged forest. Post-logging canopy cover was negativel y correlated with the number of trees extracted ha(-1). Prior to loggi ng, 65% of total gap area was contained in gaps less than 250 m(2). Af ter 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%, a nd 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 cons ervation efforts. Stem damage estimates were compared with those repor ted from uncontrolled tropical logging operations. Although absolute l evels of residual damage during controlled logging were quite low, the re was no conclusive evidence that total residual damage was relativel y lower than intensity-adjusted estimates of those other operations. I n contrast, canopy removal during logging was lower than that in two o ther neotropical studies. Both residual damage and canopy removal can be decreased further by incorporating stricter felling guidelines; mea sures to reduce necessary levels of skid trail fortification would als o decrease residual damage. The results are discussed in the broad con text of tropical forest management. A conservative approach to tropica l forestry increases the possibility of sustainable extraction of the resource. (C) 1997 Elsevier Science B.V.