The Effects of Selective Logging on Tropical Forest-Atmosphere Exchange
Miller, State University of New York at Albany, email@example.com
Goulden, University of California at Irvine, firstname.lastname@example.org
Rocha, Universidade de Sao Paulo, email@example.com
Freitas, Universidade de Sao Paulo, firstname.lastname@example.org
We are using long-term micrometerological measurements to study the effects of selective logging on carbon exchange at km 83 in the Tapajos National Forest, Para, as a component of LBA. Direct flux and concentration profile measurements of carbon dioxide and water vapor from a 67-m tall tower began a year before logging when the forest was still considered primary. The logging removed ~3.5 trees ha-1, and increased the incidence of gaps by a factor of 3 over nearby undisturbed forest. The tower measurements continued for 2.5 years after the logging. The tower observations at the selectively logged site indicate that canopy photosynthesis declined following logging, and that ecosystem respiration increased in the subsequent wet season, presumably due to decomposition of slash from the logging operation. Compared to the pre-logging period, the forest understory was drier and warmer during daytime after the logging, which would be expected to increase flammability. A third tower was installed in a large gap created by the logging to investigate whether gaps preferentially vent CO2, potentially biasing flux measurements. Comparison of data from the tower in the gap with data from the original tower in an intact patch of forest within the selectively logged area suggest that during daytime there was horizontal transport into the gap, and subsequent vertical transport out of the gap, of high-CO2, humid, cool air from the forest understory. Estimates of this CO2 “venting flux” indicate the potential for high rates of subcanopy scalar emissions out the gap; however, these estimates were uncertain because the contribution of the gap to the flux footprint is not well constrained.