6 research outputs found
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Effects of selective logging on tropical forest tree growth
We combined measurements of tree growth and carbon dioxide exchange to investigate the effects of selective logging on the Aboveground Live Biomass (AGLB) of a tropical rain forest in the Amazon. Most of the measurements began at least 10 months before logging and continued at least 36 months after logging. The logging removed ∼15% of the trees with Diameter at Breast Height (DBH) greater than 35 cm, which resulted in an instantaneous 10% reduction in AGLB. Both wood production and mortality increased following logging, while Gross Primary Production (GPP) was unchanged. The ratio of wood production to GPP (the wood Carbon Use Efficiency or wood CUE) more than doubled following logging. Small trees (10 cm < DBH < 35 cm) accounted for most of the enhanced wood production. Medium trees (35 cm < DBH < 55 cm) that were within 30 m of canopy gaps created by the logging also showed increased growth. The patterns of enhanced growth are most consistent with logging-induced increases in light availability. The AGLB continued to decline over the study, as mortality outpaced wood production. Wood CUE and mortality remained elevated throughout the 3 years of postlogging measurements. The future trajectory of AGLB and the forest's carbon balance are uncertain, and will depend on how long it takes for heterotrophic respiration, mortality, and CUE to return to prelogging levels
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Biometric and Micrometeorological Measurements of Tropical Forest Carbon Balance
We used two independent approaches, biometry and micrometeorology, to determine the net ecosystem production (NEP) of an old growth forest in Pará, Brazil. Biometric inventories indicated that the forest was either a source or, at most, a modest sink of carbon from 1984 to 2000 (+0.8 ± 2 Mg C·ha−1·yr−1; a positive flux indicates carbon loss by the forest, a negative flux indicates carbon gain). Eddy covariance measurements of CO2 exchange were made from July 2000 to July 2001 using both open- and closed-path gas analyzers. The annual eddy covariance flux calculated without correcting for the underestimation of flux on calm nights indicated that the forest was a large carbon sink (−3.9 Mg C·ha−1·yr−1). This annual uptake is comparable to past reports from other Amazonian forests, which also were calculated without correcting for calm nights. The magnitude of the annual integral was relatively insensitive to the selection of open- versus closed-path gas analyzer, averaging time, detrending, and high-frequency correction. In contrast, the magnitude of the annual integral was highly sensitive to the treatment of calm nights, changing by over 4 Mg C·ha−1·yr−1 when a filter was used to replace the net ecosystem exchange (NEE) during nocturnal periods with u* < 0.2 m/s. Analyses of the relationship between nocturnal NEE and u* confirmed that the annual sum needs to be corrected for the effect of calm nights, which resulted in our best estimate of the annual flux (+0.4 Mg C·ha−1·yr−1). The observed sensitivity of the annual sum to theu* filter is far greater than has been previously reported for temperate and boreal forests. The annual carbon balance determined by eddy covariance is therefore less certain for tropical than temperate forests. Nonetheless, the biometric and micrometeorological measurements in tandem provide strong evidence that the forest was not a strong, persistent carbon sink during the study interval
Effects of selective logging on tropical forest tree growth
We combined measurements of tree growth and carbon dioxide exchange to investigate the effects of selective logging on the Aboveground Live Biomass (AGLB) of a tropical rain forest in the Amazon. Most of the measurements began at least 10 months before logging and continued at least 36 months after logging. The logging removed similar to 15% of the trees with Diameter at Breast Height (DBH) greater than 35 cm, which resulted in an instantaneous 10% reduction in AGLB. Both wood production and mortality increased following logging, while Gross Primary Production (GPP) was unchanged. The ratio of wood production to GPP (the wood Carbon Use Efficiency or wood CUE) more than doubled following logging. Small trees (10 cm < DBH < 35 cm) accounted for most of the enhanced wood production. Medium trees (35 cm < DBH < 55 cm) that were within 30 m of canopy gaps created by the logging also showed increased growth. The patterns of enhanced growth are most consistent with logging-induced increases in light availability. The AGLB continued to decline over the study, as mortality outpaced wood production. Wood CUE and mortality remained elevated throughout the 3 years of postlogging measurements. The future trajectory of AGLB and the forest`s carbon balance are uncertain, and will depend on how long it takes for heterotrophic respiration, mortality, and CUE to return to prelogging levels.U.S. National Aeronautics and Space Administration (NASA)IBAMANASAINPECNP
Recommended from our members
Biometric and Micrometeorological Measurements of Tropical Forest Carbon Balance
We used two independent approaches, biometry and micrometeorology, to determine the net ecosystem production (NEP) of an old growth forest in Pará, Brazil. Biometric inventories indicated that the forest was either a source or, at most, a modest sink of carbon from 1984 to 2000 (+0.8 ± 2 Mg C·ha−1·yr−1; a positive flux indicates carbon loss by the forest, a negative flux indicates carbon gain). Eddy covariance measurements of CO2 exchange were made from July 2000 to July 2001 using both open- and closed-path gas analyzers. The annual eddy covariance flux calculated without correcting for the underestimation of flux on calm nights indicated that the forest was a large carbon sink (−3.9 Mg C·ha−1·yr−1). This annual uptake is comparable to past reports from other Amazonian forests, which also were calculated without correcting for calm nights. The magnitude of the annual integral was relatively insensitive to the selection of open- versus closed-path gas analyzer, averaging time, detrending, and high-frequency correction. In contrast, the magnitude of the annual integral was highly sensitive to the treatment of calm nights, changing by over 4 Mg C·ha−1·yr−1 when a filter was used to replace the net ecosystem exchange (NEE) during nocturnal periods with u* < 0.2 m/s. Analyses of the relationship between nocturnal NEE and u* confirmed that the annual sum needs to be corrected for the effect of calm nights, which resulted in our best estimate of the annual flux (+0.4 Mg C·ha−1·yr−1). The observed sensitivity of the annual sum to theu* filter is far greater than has been previously reported for temperate and boreal forests. The annual carbon balance determined by eddy covariance is therefore less certain for tropical than temperate forests. Nonetheless, the biometric and micrometeorological measurements in tandem provide strong evidence that the forest was not a strong, persistent carbon sink during the study interval