Logging damage during planned and unplanned logging operations in the eastern Amazon

Abstract

In the Paragominas region of eastern Amazonia, we compared the damage in unplanned and planned logging operations associated with each of five logging phases: (1) tree felling, (2) machine maneuvering to attach felled boles to chokers, (3) skidding boles to log landings, (4) constructing log landings and (5) constructing logging roads. Planned logging was conducted with a rubber-wheeled skidder or a bulldozer equipped with a winch, while unplanned logging was conducted with a bulldozer not equipped with a winch. We found, for each commercial tree felled, unplanned logging methods damaged 16 more trees ≥ 10 cm dbh and affected a ground area that was more than 100 m 2 greater than in planned operations. In the tree felling phase, the number of trees experiencing severe crown damage (i.e. topped) was significantly greater (Student's t-test; p < 0.002) in the unplanned operation (7.4 vs. 4.5 trees/tree felled). Similarly, the number of trees smashed to the ground was significantly greater (Student's t-test; p < 0.0006) in the unplanned operation (7.2 vs. 4.9 trees/tree felled). More trees experienced moderate or severe damage along unplanned skid trails than along planned skidder skid trails. These differences are particularly pronounced in the bole damage categories (7.9 trees ≥ 10 cm dbh smashed and 5.3 trees ≥ 10 cm dbh with moderate bole damage per 100 m of unplanned bulldozer skid trails vs. 5.3 trees smashed and 2.2 trees with moderate bole damage per 100 m of planned skidder skid trails). Per hectare logged, we found that tree felling damaged more trees ≥ 10 cm dbh than the other logging phases, with unplanned felling damaging nearly twice as mary trees per hectare as planned felling (124 vs. 64). Furthermore, the unplanned area had a lower percentage of logging gaps containing one tree in them and a higher percentage of gaps containing two, three and four felled trees. The mean area of all gaps considered together was significantly larger in the unplanned operation (Studen's t-test, p < 0.0001; 355 m 2, s.d. = 288 m 2, n = 80) than in the planned logging operation by (166 m 2, s.d. = 118 m 2, n = 108). Damage to individual trees was reduced in the planned logging operation by cutting vines 2 years prior to logging and by implementing directional felling. We estimate that the profit margins of companies that switched to planned logging methods would actually increase. The costs associated with planned logging are offset by the benefits of this approach, namely reduced machine operating time and labor per m 3 of timber extracted and less waste. Furthermore, by implementing these techniques, more than 80 trees ≥ 10 cm dbh per hectare were spared damage during logging operations. By examining the way in which individual trees were damaged and in which the ground area was disturbed in five distinet logging phases, we are able to recommend planned logging measures that can reduce overall damage to the remaining stand by 25–33% and, thus, improve the likelihood of managing these tropical forests on a 30–40 year cutting cycle