概要
On the Yucatan Peninsula in Mexico, communities (ejidos) that selectively log their forests help reduce deforestation and are an important source of timber for national and international markets. If carried out without proper planning and reduced-impact logging (RIL) practices, forest disturbances and carbon emissions from these harvests can be substantial. To assess variation in logging-induced emissions and to estimate potential reductions in those emissions, we estimated carbon impacts from damage to trees > 5 cm DBH in the annual cutting areas of ten forest-managing ejidos. Baselines were developed for emissions from felling, skidding and transport of timber and then ejidos were compared with respect to whether they were Forest Stewardship Council (FSC) certified, size of annual cutting area, logging intensity, and implementation of RIL practices, particularly directional felling, skid trail planning, and the use of small modified agricultural tractors instead of large forestry skidders. The carbon impacts of enrichment planting in multiple-tree felling gaps (400-1800 m(2)) were also evaluated. Carbon emissions from selective logging averaged 1.52 Mg m(-3) but ranged 1.19-2.55 Mg m(-3) among the 10 ejidos. Most emissions were from the remnants of trees felled for their timber (73%), followed by skidding (11%), transport infrastructure (i.e. logging roads and landings; 8%), and collateral damage from felling (7%). Our analyses indicate that FSC certification was not associated with any difference in carbon emissions from selective logging but that employment of RIL practices resulted in fewer damaged trees and lower carbon emissions even in ejidos with high logging intensities. Use of modified agricultural tractors for log yarding (i.e., skidding) reduced C emissions by 0.15 Mg m(-3) or 5 Mg km(-1) of skid trail. Greater collateral damage was found in multiple felling gaps but the increased emissions were offset by reductions in the remnants of harvest trees. Adoption of RIL-C practices by all community forestry ejidos in the region would contribute substantially to the Mexican forest sector's efforts to mitigate climate change.