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Investigation:

CD-04 (Goulden / Rocha)

LBA Dataset ID:

CD04_LEAF_LEVEL_GAS_EXCHANGE

Originator(s):

1. DOUGHTY, C.
2. SOUSA, A.
      3. FIGUEIRA, A.M.S.

Point(s) of Contact:

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Dataset Abstract:

Our understanding of the regulation of gas exchange in tropical forest ecosystems lags behind that of temperate ecosystems despite the important role tropical forests play in the global carbon cycle. This dataset includes measurements of leaf level gas exchange under a variety of experimental conditions near the LBA-ECO focal sites in the Tapajos National Forest, Para, Brazil.

Beginning Date:

2000-06-01

Ending Date:

2006-02-28

Metadata Last Updated on:

2012-02-15

Data Status:

Archived

Access Constraints:

PUBLIC

Data Center URL:

http://daac.ornl.gov/

Distribution Contact(s):

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Access Instructions:

PUBLIC

Data Access:

IMPORTANT: The LBA-ECO Project website is no longer being supported. Links to external websites may be inactive. Final data products from the LBA project can be found at the ORNL DAAC. Please follow the fair use guidelines found in the dataset documentation when using or citing LBA data.
Datafile(s):

LBA-ECO CD-04 Leaf Photosynthesis and Respiration, Tapajos National Forest: 2000-2006:  http://daac.ornl.gov/cgi-bin/dsviewer.pl?ds_id=1060

Documentation/Other Supporting Documents:

LBA-ECO CD-04 Leaf Photosynthesis and Respiration, Tapajos National Forest: 2000-2006:  http://daac.ornl.gov/LBA/guides/CD04_Leaf_Level_Gas_Exchange.html

Citation Information - Other Details:

Doughty, C., Sousa, A, and Figuera, M. 2012. LBA-ECO CD-04 Leaf Photosynthesis and Respiration, Tapajos National Forest: 2000-2006. Available on-line [http://daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. http://dx.doi.org/10.3334/ORNLDAAC/1060

Keywords - Theme:

Parameter Topic Term Source Sensor
PHOTOSYNTHESIS BIOSPHERE ECOLOGICAL DYNAMICS FIELD INVESTIGATION GAS EXCHANGE SYSTEM

Uncontrolled Theme Keyword(s):  DENDROMETERS, LEAF PHOTOSYNTHESIS, LEAF RESPIRATION, LOGGED SITE, TAPAJOS FOREST

Keywords - Place (with associated coordinates):

Region
(click to view profile)
Site
(click to view profile)
North South East West
  PARA WESTERN (SANTAREM) ) -2.75000 -3.01700 -54.95900 -54.97070

Related Publication(s):

Doughty C.E. and M.L. Goulden. 2008. Are tropical forests near a high temperature threshold?. Journal of Geophysical Research-Biogeosciences 113:G00B07, doi:10.1029/2007JG000632.

Doughty C.E. and M.L. Goulden. 2008. Seasonal patterns of tropical forest leaf area index and CO2 exchange. Journal of Geophysical Research-Biogeosciences 113: G00B06, doi:10.1080/17550874.2013.818073.

Doughty, C.E., M.L. Goulden, S.D. Miller, and H.R. da Rocha. 2006. Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest. Geophysical Research Letters 33(15): L15404, doi:10.1029/2006GL026750, 2006.

Data Characteristics (Entity and Attribute Overview):

Data Characteristics:


Leaf level photosynthesis and respiration measurements in a primary tropical rainforest, Tapajos National Forest, Para, Brazil:




Measurements of leaf level gas exchange under a variety of experimental conditions were collected from three locations in the Tapajos National Forest, south of the city of Santarem in the state of Para.




The data for this data set are presented in seven comma-delineated ASCII files.




File 1: CD04_Photosynthesis_Circadian_Santarem.csv

File 2: CD04_Photosynthesis_Temp_Curves_Santarem.csv

File 3: CD04_Photosynthesis_Warming_30_Santarem.csv

File 4: CD04_Photosynthesis_Warming_37_Santarem.csv

File 5: CD04_Photorespiration_Warming_Santarem.csv

File 6: CD04_Photosynthesis_Subcanopy_Lightcurves_Santarem.csv

File 7: CD04_Photosynthesis_Leaf_Age_Santarem.csv




Data organization:




Data organization:





File # 1

File name: CD04_Photosynthesis_Circadian_Santarem.csv

Column ,Column heading,Units/format,Explanation

----1,Set,,Unique identifier given to each set of measurements

----2,Obs,,Observation number identifies consecutive measurements within a set

----3,Common_name,,Common name

----4,Scientific_name,,Scientific name in the format Genus species

----5,Family,,Scientific family

----6,Time,seconds,Seconds since start of set, actual measurements started at 20 minutes to allow for equilibration

----7,Photo,umol CO2 m-2 s-1,Photosynthesis rate reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

----8,Cond,mol H2O m-2 s-1,Stomatal conductance reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

----9,Ci,umol CO2 mol air-1,Intercellular CO2 concentration reported as micromoles of CO2 per mol of air (umol CO2 mol air-1)

---10,VpdL,kPa,Vapor pressure deficit of the leaf reported in kilopascals (kPa)

---11,T_air,degrees C,Air temperature in the chamber in degrees Celsius (degrees C)

---12,T_leaf,degrees C,Leaf temperature in degrees Celsius (degrees C)

---13,CO2_ref,ppm,Atmospheric CO2 concentration in the reference chamber reported in parts per million (ppm)

---14,H2O_ref,mmol H2O mol air-1,Atmospheric water vapor concentration in the reference chamber reportedin millimoles of water per mole of air (mmol H2O mol air-1)

---15,RH_ref,%,Relative humidity in the reference chamber reported in percentage (%)

---16,Flow,umol s-1,Flow rate in chamber reported in micromoles of air per second (umol s-1)

---17,PARi,umol m-2 s-1,Photosynthetically active radiation (PAR) flux in the chamber reported as micromoles of photons per meter squared per second (umol m2 s-1): all wavelengths between 400 and 700 nm included in this measurement

---18,Hour,digital hours,Local time using a 24 hour clock and presented in a digital hour format. When a continuous sampling set included samples on two calender days the time values on day 2 are time +24 for ease of x axis graphing ie 25.0 = 1 am on day 2

---19,Calibration,,Observation from internal calibration mechanism




Missing data values are represented as -9999




Example data records from File #1 (CD04_Photosynthesis_Circadian_Santarem.csv )

Set,Obs,Common_name,Scientific_name,Family,Time,Photo,Cond,Ci,VpdL,T_air,T_leaf,CO2_ref,H2O_ref,RH_ref,Flow,PARi,Hour,Calibration

1,1,abiu,Micropholis sp., Sapotaceae, 1428.2, 2.16, 0.0245, 211, 0.771, 26.25, 26.04, 369.6,25.152,73.02,103.8,100,10.917,-9999

1,2,abiu,Micropholis sp., Sapotaceae, 2631.2, 2.32, 0.0237, 188, 0.777, 26.1, 26.08, 370.6,25.735,75.35,323.5,100,11.25033333,-9999

1,3,abiu,Micropholis sp., Sapotaceae, 3872.3, 2.22, 0.029, 234, 0.759, 25.8, 26.05, 369.9,26.133,77.88,622.3,100,11.58366666,-9999







File # 2

File name: CD04_Photosynthesis_Temp_Curves_Santarem.csv



Column ,Column heading,Units/format,Explanation

----1,Set,,Unique identifier given to each set of measurements

----2,Obs,,Observation number within a set

----3,Year,YYYY,Sampling date: year

----4,Month,MM ,Sampling date: month (1-12)

----5,Day,DD,Sampling date: day of month (1-31)

----6,Time,HH:MM:SS,Sampling time in local time (GMT -4) and 24 hour clock

----7,Common_name,,Common name

----8,Scientific_name,,Scientific name in the format Genus species

----9,Family,,Scientific family

---10,Photo,umol CO2 m-2 s-1,Photosynthesis rate reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

---11,Cond,mol H2O m-2 s-1,Stomatal conductance reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

---12,Ci,umol CO2 mol air-1,Intercellular CO2 concentration reported as micromols of CO2 per mol of air (umol CO2 mol air-1)

---13,VpdL,kPa,Vapor pressure deficit of the leaf reported in kilopascals (kPa)

---14,T_air,degrees C,Air temperature in the chamber in degrees Celsius (degrees C)

---15,T_leaf,degrees C,Leaf temperature in degrees Celsius (degrees C)

---16,CO2_ref,ppm,Atmospheric CO2 concentration in the reference chamber reported in parts per million (ppm)

---17,H2O_ref,mmol H2O mol air-1,Atmospheric water vapor concentration in the reference chamber reportedin millimoles of water per mole of air (mmol H2O mol air-1)

---18,RH_ref,%,Relative humidity in the reference chamber reported in percentage (%)

---19,Flow,umol s-1,Flow rate in chamber reported in micromoles of air per second (umol s-1)

---20,PARi,umol m2 s-1,Photosynthetically active radiation (PAR) flux in the chamber reported as micromoles of photons per meter squared per second (umol m2 s-1): all wavelengths between 400 and 700 nm included in this measurement



Missing data values are represented as -9999



Example data records from File #2 (CD04_Photosynthesis_Temp_Curves_Santarem.csv)

Set,Obs,Year,Month,Day,Time,Common_name,Scientific_name,Family,Photo,Cond,Ci,VpdL,T_air,T_leaf,CO2_ref,H2O_ref,RH_ref,Flow,PARi

1,1,2005,10,4,13:51:41,jarana,Lecythis lurida, Lecythidaceae, 10.1, 0.0791, 142, 1.24,26.55,29.45,368.79,28.07,79.51,500.3,999

1,2,2005,10,4,13:52:01,jarana,Lecythis lurida, Lecythidaceae, 10.4, 0.087, 154, 1.23,26.54,29.43,368.41,28.001,79.35,500.3,999

1,3,2005,10,4,13:52:22,jarana,Lecythis lurida, Lecythidaceae, 10.5, 0.0798, 134, 1.22,26.53,29.4,367.23,28.122,79.77,500.3,999




File #3

File name: CD04_Photosynthesis_Warming_30_Santarem.csv



Column ,Column heading,Units/format,Explanation

----1,Year,YYYY,Sampling date: year

----2,Month,MM,Sampling date: month (1-12)

----3,Day,DD,Sampling date: day ( 1-31)

----4,Day_of _year,day,Sampling date as day of year (1-366)

----5,Common_name,,Common name: gap refers to pioneer species found in a gap located approximately 50 m from the tower

----6,Scientific_name,,Scientific name in the format Genus species

----7,Family,,Scientific family

----8,Leaf_ID,,Leaf ID number

----9,Photo,umol CO2 m-2 s-1,Photosynthesis rate reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

---10,Cond,mol H2O m-2 s-1,Stomatal conductance reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

---11,Ci,umol CO2 mol air-1,Intercellular CO2 concentration reported as micromols of CO2 per mol of air (umol CO2 mol air-1)

---12,T_leaf,degrees C,Leaf temperature in degrees Celsius (degrees C)

---13,Warm,,Leaf warmed (1=yes, 0=no)



Missing data values are represented as -9999



Example data records from File #3 (CD04_Photosynthesis_Warming_30_Santarem.csv):



Year,Month,Day,Day_of _year, Common_name, Scientific_name, Family, Leaf_ID, Photo, Cond,Ci,T_leaf,Warm

2005,8,16,228,abiu,Micropholis sp. ,Sapotaceae ,11,2,0.017,190,30,0

2005,8,16,228,abiu,Micropholis sp. ,Sapotaceae ,12,1.7,0.015,190,30,0

2005,8,16,228,abiu,Micropholis sp. ,Sapotaceae ,13,2.5,0.025,220,30,0






File #4

File name: CD04_Photosynthesis_Warming_37_Santarem.csv



Column ,Column heading,Units/format,Explanation

----1,Year,YYYY,Sampling date year

----2,Month,MM,Sampling date month (1-12)

----3,Day,DD,Sampling date day ( 1-31)

----4,DOY,day,Sampling date in day of year (1-366)

----5,Common_name,,Common name: gap refers to pioneer species located in a gap approximately 50 m from the tower

----6,Scientific_name,,Scientific name in the format Genus species

----7,Family,,Scientific family

----8,Leaf_ID,,Leaf ID number

----9,Photo_initial,umol CO2 m-2 s-1,Initial photosynthesis rate reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

---10,Photo_post,umol m-2 s-1,Photosynthesis rate after 3-5 minutes of incubation reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

---11,Delta_photo,umol m-2 s-1,Difference between initial and post incubation photosynthesis rates

---12,Cond_initial,mol m-2 s-1,Initial stomatal conductance reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

---13,Cond_post,mol m-2 s-1,Stomatal conductance after 3-5 minutes of incubation reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

---14,Delta_cond,mol m-2 s-1,Difference between initial and post incubation conductance rates

---15,Ci_initial,umol CO2 mol air-1,Initial intercellular CO2 concentration reported as micromols of CO2 per mol of air (umol CO2 mol air-1)

---16,Ci_post,umol CO2 mol air-1,Intercellular CO2 concentration after 3-5 minutes of incubation reported as micromols of CO2 per mol of air (umol CO2 mol air-1)

---17,T_leaf,degrees C,Leaf temperature in degrees Celsius (degrees C)

---18,Warm,,Leaf warmed (1=yes, 0=no)



Missing data values are represented as -9999



Example data records from File #4 (CD04_Photosynthesis_Warming_37_Santarem.csv):

Year,Month,Day,Day_of_year,Common_name,Scientific_name,Family,Leaf_ID,Photo_initial,Photo_post,Delta_photo,Cond_initial,Cond_post,Delta_cond,Ci_initial,Ci_post,T_leaf,Warm,,,,

2005,8,16,228,abiu, Micropholis sp. ,Sapotaceae, 11, 0.5, -0.1, 0.6, 0.01, 0.005,0.005,280,360,40,0,,,,

2005,8,16,228,abiu, Micropholis sp. ,Sapotaceae, 12, -0.1, -0.3, 0.2, 0.008, 0.008,0,350,335,40,0,,,,

2005,8,16,228,abiu, Micropholis sp. , Sapotaceae, 13, 0.1, -0.4, 0.5, 0.008, 0.008,0,320,350,40,0,,,,




File #5

File name: CD04_Photorespiration_Warming_Santarem.csv



Column ,Column heading,Units/format,Explanation

----1,Year,YYYY,Sampling date: year

----2,Month,MM,Sampling date: month (1-12)

----3,Day,DD,Sampling date: day of month ( 1-31)

----4,Common_name,,Common name

----5,Scientific_name,,Scientific name in the format Genus species

----6,Family,,Scientific family

----7,Leaf_ID,,Leaf ID number

----8,Oxygen,%,Oxygen level (2% or ambient)

----9,Photo,umol CO2 m-2 s-1,Photosynthesis rate reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

---10,Cond,mol H2O m-2 s-1,Stomatal conductance reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

---11,Ci,umol CO2 mol air-1,Intercellular CO2 concentration reported as micromols of CO2 per mol of air (umol CO2 mol air-1)

---12,T_leaf,degrees C,Leaf temperature in degrees Celsius (degrees C)



Missing data values are represented as -9999



Example data records from File #5 (CD04_Photorespiration_Warming_Santarem.csv):

Year,Month,Day,Common_name,Scientific_name,Family,Leaf_ID,Oxygen,Photo,Cond,Ci,T_leaf

2005,12,16,abiu, Micropholis sp. ,Sapotaceae,11,2,2,0.035,250,36

2005,12,16,abiu, Micropholis sp. ,Sapotaceae,12,2,6.5,0.16,270,37

2005,12,16,abiu, Micropholis sp. ,Sapotaceae,21,2,2.5,0.05,260,41






File #6

File name: CD04_Photosynthesis_Subcanopy_Lightcurves_Santarem.csv

Column ,Column heading,Units/format,Explanation

----1,Set,,Unique identifier given to each set of measurements

----2,Obs,,Observation number within each set

----3,Time,HH:MM:SS,Start time for measurement set in local time (GMT -4) on a 24 hour clock

----4,Height,m,Canopy height from the ground

----5,Time,seconds,Seconds since start of measurement

----6,Photo,umol CO2 m-2 s-1,Photosynthesis rate reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

----7,Cond,mol H2O m-2 s-1,Stomatal conductance reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

----8,Ci,umol CO2 mol air-1,Intercellular CO2 concentration reported as micromols of CO2 per mol of air (umol CO2 mol air-1)

----9,VpdL,kPa,Vapor pressure deficit of the leaf reported in kilopascals (kPa)

---10,T_air,degrees C,Air temperature in the chamber in degrees Celsius (degrees C)

---11,T_leaf,degrees C,Leaf temperature in degrees Celsius (degrees C)

---12,CO2_ref,ppm,Atmospheric CO2 concentration in the reference chamber reported in parts per million (ppm)

---13,H2O_ref,mmol H2O mol air-1,Atmospheric water vapor concentration in the reference chamber reportedin millimoles of water per mole of air (mmol H2O mol air-1)

---14,RH_ref,%,Relative humidity in the reference chamber reported in percentage (%)

---15,Flow,umol s-1,Flow rate in chamber reported in micromoles of air per second (umol s-1)

---16,PARi,umol m-2 s-1,Photosynthetically active radiation (PAR) flux in the chamber reported as micromoles of photons per meter squared per second (umol m2 s-1): all wavelengths between 400 and 700 nm included in this measurement



Missing data values are represented as -9999



Example data records from File #6 (CD04_Photosynthesis_Subcanopy_Lightcurves_Santarem.csv):



Set,Obs,Time,Height,Time,Photo,Cond,Ci,VpdL,T_air,T_leaf,CO2_ref,H2O_ref,RH_ref,Flow,PARi

1,1,10:53:40,3,628.3,-1.04,0.0548,-9999,1.15,27.4,27.07,367.9,23.499,63.83,343.1,0

1,2,10:53:40,3,844.3,1.44,0.0484,308,1.14,27.28,27.06,365.4,23.615,64.6,334.3,25

1,3,10:53:40,3,1058.3,1.46,0.0456,305,1.14,27.25,27.07,366.2,23.666,64.83,316.8,50




File #7

File name: CD04_Photosynthesis_Leaf_Age_Santarem.csv



Column ,Column heading,Units/format,Explanation

----1,Year,year,Sample date: year

----2,Month,,Sample date: month (1-12)

----3,Day,,Sample date: day of the month (1-31)

----4,Day_of_Year,days,Sample date: day of the year (1-366)

----5,Common_name,,Common name

----6,Scientific_name,,Scientific name in the format Genus species

----7,Family,,Scientific family

----8,Leaf_ID,,Leaf number

----9,Photo,umol m-2 s-1,Photosynthesis rate reported as micromol CO2 fixed per meter squared of leaf area per second (umol CO2 m-2 s-1)

---10,Cond,mol m-2 s-1,Stomatal conductance reported in moles of water per meter squared leaf area per second (mol H2O m-2 s-1)

---11,Ci,umol CO2 mol air-1,Intercellular CO2 concentration reported as micromols of CO2 per mol of air (umol CO2 mol air-1)

---12,T_leaf ,degrees C,Leaf temperature in degrees Celsius (degrees C) ,

---13,Age_leaf,years,Approximate age of leaf in years ,



Missing data values are represented as -9999



Example data records from File #7 (CD04_Photosynthesis_Leaf_Age_Santarem.csv):



Year,Month,Day,Day_of_Year,Common_name,Scientific_name,Family,Leaf_ID,Photo,Cond,Ci,T_leaf ,Age_leaf

2005,10,26,299,tachi,Tachigali mymercophyla,Caesalpiniaceae,21,14,0.45,300,30,0

2005,10,26,299,tachi,Tachigali mymercophyla,Caesalpiniaceae,22,14,0.35,280,30,0

2005,10,26,299,tachi,Tachigali mymercophyla,Caesalpiniaceae,31,13,0.29,270,30,0

Data Application and Derivation:

Both modeling and observational research have focused on the direct effects of the physical environment on plant physiology. Our data address both effects of the physical environment (including light and temperature) as well as endogenous patterns (circadian rhythm) on gas exchange at the leaf level. These data are fundamental to the modeling of gas exchange at the level of the leaf or individual and inform larger-scale (Net Ecosystem Exchange) approaches as well.

Quality Assessment (Data Quality Attribute Accuracy Report):

Quality Assessment:

The data have been checked and there are no known problems at this time.

Process Description:

Data Acquisition Materials and Methods:

Site

Measurements were made between June 2000 and February 2006 at the LBA (Large-Scale Biosphere-Atmosphere Experiment in Amazonia) km 83 and 67 sites and the control site at the Seca Floresta experiment (Nepstad et al. 2002)in the Tapajos National Forest, Para, Brazil [Goulden et al., 2004; Saleska et al., 2003]. The vegetation was semidecidous closed tropical forest with canopy emergents on flat upland terrain.




Circadian rhythm:


Measurements were made between June 2000 and August 2004. The gas exchange rates of 56 leaves exposed to constant conditions for 20 to 48 hours in light and 6 leaves in darkness were measured with a LiCor 6400 gas exchange system. Plants were identified following Ribero et al. [1999]. Most of the illuminated measurements were made at a Photon Flux Density (PPFD) of 100 micromol m-2 s-1, a leaf temperature of 30 degrees C, a chamber CO2 concentration of 370 micromol mol-1 air, and either a constant chamber vapor pressure or a constant flow through the chamber. Some runs were made at a PPFD of 1000 micromol m-2 s-1 or without temperature control or without CO2 control. The neighboring leaves on the branch being tested were kept in darkness, and a larger section of the branch was shaded under a tarp, throughout each run. Leaves were accessed on the ground or from scaffolding.




Temperature curves:


We visited the field at least once a week from August to December 2004 to make photosynthesis measurements on three focal species (Sextonia rubra, Micropholis sp., Lecythis lurida) using a portable gas exchange system (LI 6400, Li-Cor Biosciences, Lincoln, NE). We made repeated measurements of the response of leaf gas exchange to irradiance, holding leaf temperature constant at 30 degrees C, and the response to leaf temperature, holding flow, irradiance and CO2 concentration constant. The temperature response curves were made by placing leaves in the chamber at 30 degrees C and 1000 micromol m-2s-1, allowing conditions to equilibrate for several minutes, and then raising the temperature in the chamber while recording the observations every 20 seconds. Each temperature response curve took 10 to 20 minutes, and the maximum achievable temperature was approximately 42 degrees C. Observations immediately after the initial temperature increase were often out of calibration and were removed from subsequent analysis. Rising temperature increased evaporative demand and Vapor Pressure Deficit (VPD) and decreased relative humidity (RH). The changes in temperature, VPD and RH were tightly correlated, and we were unable to determine which factor was better correlated with the rates of gas exchange.




Effect of warming:


The field campaign lasted from July 2005 to February 2006 and focused on six canopy top tree species and two canopy top liana species accessed with three canopy access towers and 6 gap specialist species in a gap at km-83. We studied two species accessible from a 30-m scaffold tower at the LBA-ECO km-83 site, four species from a 45-m scaffold tower at km-67, and two species from a 30-m tower at the control site Seca Floresta. We tested the following eight canopy top species: Abuta sp., Copaifera ducke, Protium punticulatum Macbri, Caraipa sp., Tachigali mymercophyla, Sextonia rubra, Micropholis sp., Serjania sp. In a gap approximately 50 meters from the km 83 eddy flux tower we tested the following gap species: Protium sp., Mabea subsessilis, Cecropia sciadophylla, Cariniana micrantha, Mabea sp., Iryanthera sagotiana.

We measured leaf-level gas exchange once a week at all sites from July 2005 to February 2006 using a portable gas exchange system (LI 6400, Li-Cor Biosciences, Lincoln, NE). We measured the rates of gas exchange under a standardized set of conditions (temperature 30 degrees C and approximately 37 degrees C; PPFD 1000 micromol m-2s-1; ambient CO2). We repeatedly measured two leaves on each of four branches on each of the eight canopy species (n=64 each week), and returned to a leaf until it abscised, at which point we choose another nearby leaf. We measured 2 leaves each week on each of the 6 gap species (n = 12). Each gas exchange measurements lasted approximately 3-5 minutes and the data was averaged once the measurement stabilized.

We used electric resistance heaters powered by solar panels to continuously warm four individual leaves for each species. Each heater was composed of a constantan wire (30 ohms) wrapped in aluminum foil and folded into approximately 40 cm2. We ran 6 volts through the wire (1.2 Watts) and placed the heaters approximately 2 cm below the leaves by attaching them to the petiole with wire. A nighttime comparison of leaf temperatures between 5 heated leaves and a non-heated leaf on a night when the leaf thermocouple positions were verified, showed the electric resistance heaters warmed the leaves by an average of 1.96 degrees C plus/minus 1.4 degrees C(sd) at night.

We measured photosynthesis at 2 percent oxygen to estimate the rate of photorespiration. We varied the composition of the air entering the gas exchange system by mixing 10 percent ambient air with 90 percent pure nitrogen from a tank, thereby reducing the oxygen concentration entering the system to approximately 2 percent. The gas mixture was then scrubbed of CO2, and pure CO2 was injected to bring the CO2 mixing ratio to 370 ppm. We determined the rates of photorespiration for leaves at 1000 micromol m-2s-1 and 30 and 37 degrees C. The gas exchange observations at 37 degrees C were recorded before significant stomatal closure.






Effect of leaf age:


We measured the leaf-level gas exchange off scaffold towers (Doughty et al. 2006; Doughty and Goulden 2008) at the LBA-ECO km-83, km-67, and Seca Floresta field sites. The km-83 scaffold was located within 300 meters of the main eddy flux tower.

We used a portable gas exchange system (LI 6400, Li-Cor Biosciences, Lincoln, NE) at the km-83 site from August to December 2004 and at all of the sites from August to January 2005. We measured the rates of gas exchange under a standardized set of conditions (temperature 30 degrees C; PPFD 1000 micromol m-2s-1; ambient CO2). We repeatedly measured two leaves on each of two branches for canopy species, and returned to a leaf until it abscised, at which point we choose another nearby leaf.




Sub-canopy measurements:


We measured leaf-level gas exchange using scaffold towers at the LBA-ECO km-83, km-67 field sites. We measured the following sub-canopy and understory species: Eschweilera amazonica, Lecythis sp., Chimarrhis turbinate, Faramea platyneura, Sclerolobium paraense.

We used a portable gas exchange system (LI 6400, Li-Cor Biosciences, Lincoln, NE) in April and May 2002 to measure the rates of gas exchange under various irradiance levels (PPFD 0, 50, 100, 200, 500, 1000, 1500, 1800 micromol m-2 s-1) at constant temperature (30 degrees C) and ambient CO2. We grouped the data as understory (0-10 meters), and sub-canopy species (10-25 meters).

References:

Doughty, CE, ML Goulden, SD Miller and HR da Rocha. 2006. Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest. Geophysical Research Letters 33: L15404, doi:10.1029/2006GL026750.



Doughty, CE, and ML Goulden. 2008. Are tropical forests near a high temperature threshold? J. Geophys. Res., 113, G00B07, doi:10.1029/2007JG000632.



Goulden, ML et al., 2004. Diel and seasonal patterns of tropical forest CO2 exchange. Ecological Applications 14: S24-S54.



Nepstad DC, Moutinho P, Dias MB, Davidson E, Cardinot G, Markewitz D, Figueiredo R, Vianna N, Chambers J, Ray D, Guerreiros JB, Lefebvre P, Sternberg L, Moreira M, Barros L, Ishida FY, Tohlver I, Belk E, Kalif K, and K Schwalbe 2002. The effects of partial throughfall exclusion on canopy processes, aboveground production, and biogeochemistry of an Amazon forest JGR- Atmospheres, 107 D20 Article Number: 8085.



Ribero, JE et al. 1999. Flora da Reserva Ducke (in Portuguese), 799 pages Dep. for Int. Dev. Manaus, Brazil.



Saleska, SR et al., 2003. Carbon in Amazon forests: Unexpected seasonal fluxes and disturbance-induced losses. Science 302: 1554-1557.

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