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CD-04 Abstract

Measuring the Effects of Logging on the CO2 and Energy Exchange of a Primary Forest in Tapajós National Forest

Michael L. Goulden — University of California Irvine (US-PI)
Humberto Rocha — USP (Universidade de Sao Paulo) (SA-PI)

We propose to continue investigating the effects of selective logging on the

exchanges of CO2 and energy by a primary forest in the Tapajos National Forest (TNF),

Pará. Our study can be thought of as a large experimental manipulation, where

we use a range of techniques, including eddy covariance, to monitor forest

physiology before, during, and after selective logging.

We have been making eddy covariance measurements, and ground-based measurements

of soil respiration, litterfall, wood increment, and coarse woody debris, at the

Santarem km-83 site since 2000. As of March 2002 we had collected, and submitted

to Beija-Flor, 20 months of nearly continuous tower-flux observations.  The

first 14 months of observations were made while the forest was relatively

undisturbed.  These data served as the basis for three submitted

manuscripts that detail the exchanges of CO2 and energy by the intact forest.

The remaining 6 months of observations were made after the forest was

selectively logged in September 2001. The logging operation, which was conducted

by a local firm using reduced impact procedures, covered ~400-ha of forest that

extended ~2-km upwind of the tower. The loggers removed only ~6% of the biomass

in large trees, but left another ~18% of the biomass in large trees as slash,

and eliminated ~13% of the canopy on an area basis.  Preliminary analysis

of the tower observations indicate that canopy photosynthesis declined by ~15%

following logging, and that ecosystem respiration increased in the subsequent

wet season. 

In this proposal we request support to complete our study by continuing these

observations for three more years.  Our goal is to use the combined tower

and ground-based observations to quantify the forest’s response to, and

recovery from, logging. We will do this in collaboration with other researchers

working in Santarem, and, in particular those making flux measurements at the

km-67 tower (CD10, Wofsy PI; TG07, Keller and Crill PIs), which serves as an

undisturbed control for the km-83 tower, and those making additional

measurements at the km-83 tower (TG07, Keller and Crill PIs; CD03 Fitzjarrald

PI, and TG04,  Martens PI).  Additionally, we will focus efforts on

scientific integration within LBA, both among researchers working in Santarem,

and among all tower groups within LBA.  Finally, we will continue our

educational activities by further involving Brazilian students in the research,

both at UCI and USP, as well as in Santarem.

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