We used eddy covariance and ecological measurements to investigate the effects of reduced impact logging (RIL) on an old-growth Amazonian forest. Logging caused small decreases in gross primary production, leaf production, and latent heat flux, which were roughly proportional to canopy loss, and increases in heterotrophic respiration, tree mortality, and wood production. The net effect of RIL was transient, and treatment effects were barely discernable after only 1 y. RIL appears to provide a strategy for managing tropical forest that minimizes the potential risks to climate associated with large changes in carbon and water exchange. ) of human-induced CO 2 emissions during [2000][2001][2002][2003][2004][2005][2006] (1), while increasing land-surface albedo and decreasing available energy and evapotranspiration (2). The changes in surface-energy exchange and increase in atmospheric CO 2 associated with largescale tropical deforestation are predicted to alter precipitation patterns (3, 4) and cause a net warming of global climate (5, 6). The avoidance of tropical deforestation as a means to slow the rise of atmospheric carbon dioxide, while maintaining the role of forest in the water and energy cycles and sustaining biodiversity and other environmental services, is a key climate change mitigation goal (e.g., the United Nations program Reducing Emissions from Deforestation and Forest Degradation) (7,8).The harvesting of marketable trees by selective logging in the Brazilian Amazon has occurred at an areal rate comparable to deforestation (1-2 × 10 4 km 2 y −1 between 1996 and 2002) (9-11). Conventional logging (CL) is highly damaging to forest canopy, residual vegetation, and soil (12), and increases forest susceptibility to fire (11). The estimated gross CO 2 emission to the atmosphere from CL in the Amazon amounts to 25% of that due to deforestation (9). In contrast, reduced impact logging (RIL) is intended to minimize the disruption of tropical forest carbon and water cycles (13) via preharvest tree selection and vine cutting, directional felling, and planned extraction (skid) trails and log decks. RIL has been shown to reduce canopy destruction (12, 14-16); however, the effects of RIL on land-atmosphere gas and energy exchange have not been well quantified.We report direct measurements of the net effect of RIL on tropical forest carbon, water, and energy exchange. Two sites in the Tapajos National Forest (TNF) were studied as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (17), denoted by distance south of Santarem, Para, Brazil (Fig. S1): "km 67" (unlogged control site, 2.85667 S, 54.958889 W) and "km 83" (logged site, 3.01803 S, 54.97144 W). The logging was conducted by a local commercial firm (Empresa Agropecuária Treviso Ltda), with oversight from the Brazilian Institute for the Environment and Renewable Resources. Parallel measurements at control and logged sites began 6-12 mo before logging, and continued at least 29 mo afterward. Our measurements focused on aspects of tropical fore...
