Micrometeorology of a Tropical Rainforest Before and After...
1
Micrometeorology of a Tropical Rainforest Before and After Selective Logging Scott Miller ([email protected]), Mike Goulden, Mary Menton, Ed Read, Rob Elliot, University of California, Irvine Humberto da Rocha, Helber Freitas, Michela Figuera, Albert da Sousa, Universidade de Sao Paulo, Brazil We are using micrometeorology to study carbon exchange between a tropical forest and the atmosphere in Tapajos National Forest, Para, Brazil. Continuous eddy covariance and profile storage measurements began in June 2000 from a 65 meter tall tower (photo at right). The forest in the “footprint” of the tower measurements remained intact (or primary) for the first 14 months of measurements. We used these data, along with biomass measurements based on 3 forest inventories between 1984 and 2000 that include the tower footprint, to establish a carbon balance for this site (see Pre-Logging Carbon Balance and Night-time Problems). Between September and December 2001, 700 hectares of forest, including the tower footprint, were selectively logged. The instruments remained in place during the logging, and measurements have continued to the present. Ground based surveys were conducted after the logging to quantify the extent of the logging. We are comparing the micrometeorological measurements from before and after the logging to assess its impact on the carbon cycling of the forest (see Effect of Selective Logging). The micrometeorology of forest gaps, both natural and due to logging, are of interest because they may behave differently than intact forest. In terms of carbon dioxide exchange, they possibly act as chimneys with preferential venting of CO2 that may not be dectected by eddy covariance. To study the microclimate of gaps, after the logging an additional 65 meter tall tower was installed 400 meters upwind (east) of the original tower, in a large gap created by the logging. This tower was instrumented similar to the original tower, and data from the two towers are being compared to address the affect of gaps. (see Tower Inter-Comparison and Gap Micrometeorology). OVERVIEW AND MEASUREMENTS TOWER INTER-COMPARISON AND GAP MICROMETEOROLOGY THE NIGHT TIME PROBLEM • The “raw” tower-based carbon balance indicated a big sink, consistent with other tower-based results in Amazonia (Malhi et al. 1998, Figure 1). But, biomass inventories at the site spanning 16 years (1984 to 2000) indicated approximate carbon balance, or a small carbon source (Figure 1). • The tower-based result likely overestimates C uptake due to underestimation of respiration during calm, stable nocturnal periods. Applying a so-called u*-filter, where NEE during night time periods with little turbulent mixing are replaced with observations from more turbulent periods (Figure 2), had a dramatic affect on the annual sum, and reconciles the tower- and biomass results (Figure 1). Thanks to: Fernando Alves Leão, Roberto Cardoso, Daniel Amarel, Miranda Silva, Dan Hodkinson, Lisa Zweede and Bethany Reed, IBAMA, and INPE, and NASA. 4 km 4 km EFFECT OF SELECTIVE LOGGING TOWER TOP (64 m) Momentum Flux CSAT3 Heat Flux CSAT3 CO2/H2O Flux (1) LiCor 7500 CO2/H2O Flux (2) LiCor-7000 PAR (up/down) LiCor Solar Radiation Kipp & Zonen Net Radiation REBS Q*7 Rain Tipping Bucket PRE-LOGGING CARBON BALANCE AND NIGHT-TIME PROBLEMS Figure 9 Average Daily Cycles of NEE BLUE: PRE-LOGGING GREEN: POST-LOGGING Dry Season Wet Season 65 meter tower 65 meter tower PROFILE MEASUREMENTS CO2/H2O LI-7000 (12 levels, 0.1 to 64 m) Wind speed Cups (64, 50, 40 m) Wind vector 2D Sonics (30, 20, 1.3 m) Temperature CS107 (64, 40, 30, 20, 10, 2 m) JUL 1999 JUL 2000 JUL 2001 JUL 2002 JAN 2000 JAN 2002 JAN 2001 Time Line Site is Logged Select site Infrastructure Installed Ground-Based Measures begin Tower measurements begins Second tower installed Soil chambers installed Logging Extent Measured Undisturbed Baseline Logged Forest We were concerned that forest gaps (both natural and due to logging) correspond to altered radiation environments that create the possibility of localized preferential exchange of CO2 (venting) that is missed by eddy covariance. A second 65 meter tower was installed in a large gap created by the logging, about 400 meters east (upwind) of the original tower, and was instrumented for eddy flux (open path IRGA), and profile measurements (LiCor 7000), similar to the original tower (Figure 11 and photo). Preliminary analyses indicate that, to first order, the mean quantities and fluxes (averaged over 70 days) from the two towers are remarkably similar (Figures 12-17). This suggests that gaps do not act as significant preferential pathways for exchange between the forest and atmosphere. Biometry Raw data -4 T C ha-1 yr-1 1 year Figure 1 Figure 1 TOWER TOP INSTRUMENTS TOWER TOP INSTRUMENTS ELEVATOR CARRIAGE ELEVATOR CARRIAGE Km 83 Km 83 TOWER TOWER ELEVATOR PROFILES • The elevator used to lower instruments for servicing provides a unique opportunity to examine the structure of the forest microclimate. The barometric sensor mounted to the elevator allows us to approximate the altitude of the elevator (Figure 3A). It takes about 11 minutes to raise or lower. • The profile shown was made at 6:30pm local time (after sundown). The temperature shows a sharp increase at the canopy height of 35 meters (Figure 3D) - this thin stable layer acts to decouple the air above and below, as evidenced in the reduced winds below 35 meters (Figure 3B). • The wind direction below the inversion is more variable, and below 20 meters is 90 degrees different than the wind direction above the canopy (Figure 3C). • The CO2 respired by plants and soil has begun to accumulate below the inversion as the stable layer inhibits mixing with above canopy air (Figure 3E) Figure 3 Figure 3 Figure 2 Figure 2 Bottom, t=0 Bottom, t=0 Top, t~11 Top, t~11 minutes minutes Elevator Elevator going up going up u*-filtered data +0.4 T C ha-1 yr-1 BR 163 BR 163 Tower Tower Figure 4 Logging Map Figure 4 Logging Map About 700 hectares was logged between September and December 2001 (Time Line and Figure 4, area outlined in green). After the logging, ground-based measurements were made to quantify the extent of the logging disturbance (Figures 5, 6, 7, 8). The daily cycles of Net Ecosystem Exchange (NEE) during the 2001 dry season after the harvest showed less afternoon uptake and less nighttime efflux (respiration) than during the 2000 pre-harvest dry season (Figure 9). The reduction is of order 15%, consistent with the fraction of gaps left by the logging (Figure 8). However, the difference between pre- and post-logging during wet season is less, suggesting the forest may begin its recovery quickly. The km 67 tower*, in an un-logged area of the same forest (16 km north), acts as a control for the logging experiment. The two towers show close agreement in net carbon exchange prior to the logging (Figure 10, a u*-filter with threshold of 0.2 ms -1 was applied to both datasets, see Pre-Logging Carbon Balance and Night-time Problems ). After the logging there was greater carbon loss than at the control site, a combination of decreased production (due to less leaf area) and increased respiration (due to increased slash created by the logging). We will continue to monitor the forest’s recovery over the next few years. * Km 67 data provided by Wofsy, et al. •2-3 trees ha-1 removed • 5 T C ha-1 wood removed Figure 5 Logging Patio Figure 5 Logging Patio •15 T C ha-1 slash introduced Figure 6 Figure 6 8% impacted by roads/skid trails Figure 7 Figure 7 Figure 8 Gap Map Figure 8 Gap Map Total 10-15% Total 10-15% Km 67 Km 67 TOWER TOWER (control) (control) Figure 10 Comparison with km 67 tower Figure 10 Comparison with km 67 tower Cumulative NEE Cumulative NEE Logging period is Logging period is shaded gray shaded gray Post-logging IKONOS image. Gaps created by the logging appear in pink. 600 m x Figure 11 Figure 11 Tower 2 Tower 2 Tower 1 Tower 1 Figure 12 Figure 12 Figure 15 Figure 15 Figure 16 Figure 16 Figure 17 Figure 17 Figure 14 Figure 14 Figure 13 Figure 13 Three papers have been accepted to the Ecological Applications LBA special issue based on the year of data before logging: Miller et al. Tower-based and Biometry-based Measurements of Tropical Forest Carbon Balance Goulden et al. Physiological Controls on Tropical Forest CO2 Exchange Rocha et al. Seasonality of Water and Heat Fluxes Over a Tropical Forest in Eastern Amazonia Drafts are available at http://www.ess.uci.edu/~lba/safe (username: cd04, password: secure)
Transcript of Micrometeorology of a Tropical Rainforest Before and After...
Micrometeorology of a Tropical Rainforest Before and After Selective Logging Scott Miller ([email protected]), Mike Goulden, Mary Menton, Ed Read, Rob Elliot, University of California, Irvine
Humberto da Rocha, Helber Freitas, Michela Figuera, Albert da Sousa, Universidade de Sao Paulo, Brazil
Micrometeorology of a Tropical Rainforest Before and After Selective Logging Scott Miller ([email protected]), Mike Goulden, Mary Menton, Ed Read, Rob Elliot, University of California, Irvine
Humberto da Rocha, Helber Freitas, Michela Figuera, Albert da Sousa, Universidade de Sao Paulo, Brazil
We are using micrometeorology to study carbon exchange between a tropicalforest and the atmosphere in Tapajos National Forest, Para, Brazil. Continuouseddy covariance and profile storage measurements began in June 2000 from a65 meter tall tower (photo at right).
The forest in the “footprint” of the tower measurements remained intact (orprimary) for the first 14 months of measurements. We used these data, alongwith biomass measurements based on 3 forest inventories between 1984 and2000 that include the tower footprint, to establish a carbon balance for this site(see Pre-Logging Carbon Balance and Night-time Problems).
Between September and December 2001, 700 hectares of forest, including thetower footprint, were selectively logged. The instruments remained in placeduring the logging, and measurements have continued to the present. Groundbased surveys were conducted after the logging to quantify the extent of thelogging. We are comparing the micrometeorological measurements from beforeand after the logging to assess its impact on the carbon cycling of the forest(see Effect of Selective Logging).
The micrometeorology of forest gaps, both natural and due to logging, are ofinterest because they may behave differently than intact forest. In terms ofcarbon dioxide exchange, they possibly act as chimneys with preferentialventing of CO2 that may not be dectected by eddy covariance. To study themicroclimate of gaps, after the logging an additional 65 meter tall tower wasinstalled 400 meters upwind (east) of the original tower, in a large gap createdby the logging. This tower was instrumented similar to the original tower, anddata from the two towers are being compared to address the affect of gaps.(see Tower Inter-Comparison and Gap Micrometeorology).
OVERVIEW AND MEASUREMENTS
TOWER INTER-COMPARISON AND GAP MICROMETEOROLOGY
THE NIGHT TIME PROBLEM
• The “raw” tower-based carbon balance indicated a big sink,consistent with other tower-based results in Amazonia (Malhi etal. 1998, Figure 1). But, biomass inventories at the sitespanning 16 years (1984 to 2000) indicated approximate carbonbalance, or a small carbon source (Figure 1).
• The tower-based result likely overestimates C uptake due tounderestimation of respiration during calm, stable nocturnalperiods. Applying a so-called u*-filter, where NEE during nighttime periods with little turbulent mixing are replaced withobservations from more turbulent periods (Figure 2), had adramatic affect on the annual sum, and reconciles the tower-and biomass results (Figure 1).
Thanks to: Fernando Alves Leão, Roberto Cardoso, Daniel Amarel, Miranda Silva,Dan Hodkinson, Lisa Zweede and Bethany Reed, IBAMA, and INPE, and NASA.
4 km4 km
EFFECT OF SELECTIVE LOGGING
TOWER TOP (64 m)
Momentum Flux CSAT3Heat Flux CSAT3CO2/H2O Flux (1) LiCor 7500CO2/H2O Flux (2) LiCor-7000PAR (up/down) LiCorSolar Radiation Kipp & ZonenNet Radiation REBS Q*7Rain Tipping Bucket
PRE-LOGGING CARBON BALANCE AND NIGHT-TIME PROBLEMS
Figure 9 Average Daily Cycles of NEE
BLUE: PRE-LOGGINGGREEN: POST-LOGGING
Dry Season Wet Season
65 meter tower65 meter tower
PROFILE MEASUREMENTS
CO2/H2O LI-7000 (12 levels, 0.1 to 64 m)Wind speed Cups (64, 50, 40 m)Wind vector 2D Sonics (30, 20, 1.3 m)Temperature CS107 (64, 40, 30, 20, 10, 2 m)
JUL 1999 JUL 2000 JUL 2001 JUL 2002JAN 2000 JAN 2002JAN 2001
Time Line
Site is Logged
Select site Infrastructure Installed
Ground-Based Measures begin
Tower measurements begins
Second tower installed
Soil chambers installed
Logging Extent Measured
Undisturbed Baseline
Logged Forest
We were concerned that forest gaps (both natural and due to logging)correspond to altered radiation environments that create the possibility oflocalized preferential exchange of CO2 (venting) that is missed by eddycovariance.
A second 65 meter tower was installed in a large gap created by thelogging, about 400 meters east (upwind) of the original tower, and wasinstrumented for eddy flux (open path IRGA), and profile measurements(LiCor 7000), similar to the original tower (Figure 11 and photo).
Preliminary analyses indicate that, to first order, the mean quantities andfluxes (averaged over 70 days) from the two towers are remarkably similar(Figures 12-17). This suggests that gaps do not act as significantpreferential pathways for exchange between the forest and atmosphere.
Biometry
Raw data -4 T C ha-1 yr-1
1 year
Figure 1Figure 1
TOWER TOP INSTRUMENTSTOWER TOP INSTRUMENTS
ELEVATOR CARRIAGEELEVATOR CARRIAGE
Km 83Km 83TOWERTOWER
ELEVATOR PROFILES
• The elevator used to lower instruments for servicing provides a uniqueopportunity to examine the structure of the forest microclimate. Thebarometric sensor mounted to the elevator allows us to approximate thealtitude of the elevator (Figure 3A). It takes about 11 minutes to raise or lower.
• The profile shown was made at 6:30pm local time (after sundown). Thetemperature shows a sharp increase at the canopy height of 35 meters (Figure3D) - this thin stable layer acts to decouple the air above and below, asevidenced in the reduced winds below 35 meters (Figure 3B).
• The wind direction below the inversion is more variable, and below 20 metersis 90 degrees different than the wind direction above the canopy (Figure 3C).
• The CO2 respired by plants and soil has begun to accumulate below theinversion as the stable layer inhibits mixing with above canopy air (Figure 3E)
Figure 3Figure 3
Figure 2Figure 2
Bottom, t=0Bottom, t=0
Top, t~11 Top, t~11 minutesminutes
ElevatorElevatorgoing upgoing up
u*-filtered data+0.4 T C ha-1 yr-1
BR
163
BR
163TowerTower
Figure 4 Logging MapFigure 4 Logging Map
About 700 hectares was logged between September and December 2001 (TimeLine and Figure 4, area outlined in green). After the logging, ground-basedmeasurements were made to quantify the extent of the logging disturbance(Figures 5, 6, 7, 8).
The daily cycles of Net Ecosystem Exchange (NEE) during the 2001 dry seasonafter the harvest showed less afternoon uptake and less nighttime efflux(respiration) than during the 2000 pre-harvest dry season (Figure 9). Thereduction is of order 15%, consistent with the fraction of gaps left by the logging(Figure 8). However, the difference between pre- and post-logging during wetseason is less, suggesting the forest may begin its recovery quickly.
The km 67 tower*, in an un-logged area of the same forest (16 km north), actsas a control for the logging experiment. The two towers show close agreementin net carbon exchange prior to the logging (Figure 10, a u*-filter with thresholdof 0.2 ms-1 was applied to both datasets, see Pre-Logging Carbon Balance andNight-time Problems ). After the logging there was greater carbon loss than atthe control site, a combination of decreased production (due to less leaf area)and increased respiration (due to increased slash created by the logging).
We will continue to monitor the forest’s recovery over the next few years.
* Km 67 data provided by Wofsy, et al.•2-3 trees ha-1 removed• 5 T C ha-1 wood removed
Figure 5 Logging PatioFigure 5 Logging Patio
•15 T C ha-1 slash introduced
Figure 6Figure 6
8% impacted by roads/skid trails
Figure 7Figure 7 Figure 8 Gap MapFigure 8 Gap Map
Total 10-15%Total 10-15%
Km 67Km 67TOWERTOWER(control)(control)
Figure 10 Comparison with km 67 towerFigure 10 Comparison with km 67 tower
Cum
ulat
ive
NE
EC
umul
ativ
e N
EE Logging period isLogging period is
shaded grayshaded gray
Post-logging IKONOS image.Gaps created by the loggingappear in pink.
600 m
xx
Figure 11Figure 11 Tower 2Tower 2
Tow
er 1
Tow
er 1
Figure 12Figure 12
Figure 15Figure 15 Figure 16Figure 16 Figure 17Figure 17
Figure 14Figure 14Figure 13Figure 13
Three papers have been accepted to the Ecological Applications LBA special issue based on the year ofdata before logging:
Miller et al. Tower-based and Biometry-based Measurements of Tropical Forest Carbon BalanceGoulden et al. Physiological Controls on Tropical Forest CO2 ExchangeRocha et al. Seasonality of Water and Heat Fluxes Over a Tropical Forest in Eastern Amazonia
Drafts are available at http://www.ess.uci.edu/~lba/safe (username: cd04, password: secure)
