An Assessment of Soil Compaction after Logging Operations in Central Amazonia

In the forests of the Amazon Basin, there are still few studies on soil compaction caused by logging activities. This study evaluated an operation located on the property of a timber company in Central Amazonia, which uses harvesting techniques based on the harvesting system developed by the Centre for Agricultural Research in Suriname. The timber-extraction method employed by the timber company consists of three activities: (1) skid trail construction with a track-type tractor, (2) log winching with a winch attached to the tractor, and (3) log skidding with a rubber-tired skidder. Soil bulk density and soil penetration resistance were quantified to 20 cm in depth. After a single tractor ingress and egress for trail construction, the soil incurred an increased root growth-limiting bulk density and penetration resistance. However, log winching did not cause significant soil compaction. The conclusions of the study were: (1) the greatest impact from this harvesting system came from the skid trail construction, (2) the technique of log winching limited forest floor compaction and disturbance that damages forest regeneration, and (3) log skidding during dry soil conditions limited increases in compaction and track formation. Study Implications: Ground-based logging operations in the Brazilian Amazonia incur numerous impacts on forest regeneration and soil structure. Presently, government agencies and the timber industry are aware of soil degradation because of unrestricted skidding operations. An alternative to this is to apply harvesting systems that incorporate a winching capability. The implementation of a winch has proven to be successful in limiting forest-floor disturbance. The development of alternative and site-specific logging techniques is necessary for the long-term viability for forest management in this region. This study demonstrates that it is possible to limit the detrimental and long-lasting impacts on soil, specifically compaction. Reducing traffic of heavy machinery will contribute to the diminution of deleterious effects on the ground vegetation and forest regeneration. This is accomplished with the combination of preplanned designated skid trails and the use of winching cables. The capability of winching enables a greater distance between skid trails, which avoids unnecessary machine traffic within the logging area. Current training programs on low-impact logging by nongovernment organizations and state and federal agencies in the Amazon region would benefit from including winching techniques, with an aim toward lowering impacts on soil compaction and forest regeneration during harvesting operations.