TITLE

Patterns and Controls of Temporal Variation in Net Ecosystem CO₂ Exchange in Arctic old tussock tundra Ecosystem

AUTHORS

Principal Investigator

Walter C. Oechel

Professor of Biology

Department of Biology

San Diego State University

5500 Campanile Dr.

San Diego, California 92182-4614

Telephone: (619) 594-4818 or (619) 594 6613

FAX: (619) 594-5676

E-Mail: oechel@sunstroke.sdsu.edu

Web Pages: http://www.sci.sdsu.edu/GCRG/

Allen S. Hope

Professor of Geography

Department of Geography

San Diego State University

5500 Campanile Dr.

San Diego, California 92182-4493

Telephone: (619) 594-2777

E-Mail: hope1@mail.sdsu.edu

Web Page: http://geography.sdsu.edu/People/Faculty/hope.html

Douglas A. Stow

Professor of Geography

Department of Geography

San Diego State University

5500 Campanile Dr.

San Diego, California 92182-4493

Telephone: (619) 594-5498

E-Mail: stow@mail.sdsu.edu

Web Pages:

http://geography.sdsu.edu/Research/Projects/NASA_ARC/INDEX.HTM

http://geography.sdsu.edu/Research/Projects/NASA_habitat/index.htm

http://geography.sdsu.edu/Research/Projects/Aftweb/AFT-main.htm

George Vourlitis

Associate Professor of Biological Sciences

Department of Biological Sciences

California Sate University, San Marcos

333 S. Twin Oaks Valley Rd.
San Marcos, CA 92096

Telephone: (760) 750-4119

E-Mail: georgev@csusm.edu
Web Pages: http://www.csusm.edu/Biology/bios/vourlitis.htm

Primary contact for data information

Joe Verfaillie

Staff

Department of Biology

San Diego State University

5500 Campanile Dr.

San Diego, California 92182-4614

Telephone: (619) 594-7421

FAX: (619) 594-5676

E-Mail: josephv@sunstroke.sdsu.edu

Web Pages: http://www.sci.sdsu.edu/GCRG/

Filed Research Assistants

Dmitri Karelin

Hyojung Kwon

Rommel Zulueta

Steve Hasting

FUNDING SOURCE AND GRANT NUMBER

LAII-2 Regional Variability in carbon and energy fluxes: Toward global synthesis (OPP – 9732105)

TECO Patterns and Controls of Temporal Variation in CO₂ Sequestration and Loss in Arctic Ecosystems (OPP – 973004)

DATA SET OVERVIEW

Data Set Description: the measurements of mass (CO₂ and H₂O) and energy fluxes and meteorological conditions were conducted in Seward, Alaska using tower-based eddy covariance method. Meteorological data were measured along with the eddy covariance tower. The objectives of the research were to determine the patterns and controls on the temporal variability of the mass and energy fluxes at the old tussock tundra ecosystem and to understand the spatial variability of the mass and energy fluxes over different tundra ecosystems. The measurements 2000 were conducted with an emphasis of understanding spatial variability in the mass and energy fluxes, while the measurement in 2001 conducted with an emphasis of understanding temporal variability in the mass and energy fluxes.

Measurement Period and Location:

	2000			2001
	Young Tussock Tundra ^†	Shrub Tundra	Old Tussock Tundra	Old Tussock Tundra
Observation Period	July 25 – 29	July 29 – August 2	August 2 – August 6	June 5 to August 25
Location	65^o 26.40 N 164^o 34.73W	65^o 27.29 N 164^o 37.77W	65^o 25.76N 164^o 38.72 W	65^o 25.76N, 164^o 38.72 W
Elevation	885 feet	725 feet	291 feet	291 feet
Ecosystem Type	Stiped	Salix Veg.	Typical tussock Tundra	Typical tussock Tundra

^† Young tussock tundra site was burned 1996.

INSTRUMENT DESCRIPTION

§ Measuring Ecosystem Carbon and Water Vapor Exchange

Measurement of CO₂ and water vapor fluxes and energy balance was made using tower-based eddy covariance techniques. Fluctuations in vertical, streamwise and lateral wind speed and temperature were measured at 10 Hz using a three-dimensional sonic anemometer (Model R3, Gill Instruments, England). CO₂ and water vapor fluctuations were measured using an open-path gas analyzer (Model LI-7500, LI-COR, Inc., Lincoln, Nebraska) in 2001. Calibration of the open-path was executed every 10 days using a 400 ppm. standard gas and a portable dew-point generator (Model LI-610, LI-COR, Inc., Lincoln, Nebraska). Raw CO₂ and H₂O vapor fluctuations were output as mean voltages and converted to concentrations by multiplying by the requisite calibration constant. Net CO₂, water vapor and sensible heat fluxes were computed following coordinate rotations of the vertical, horizontal and streamwise axes. Fast response (10 Hz) fluxes were calculated and stored on a personal computer as 30 minutes averages. CO₂ and water vapor flux estimates were corrected for the variation in air density due to simultaneous transfers of water vapor and sensible heat according to Webb et al. (1980).

§ Measuring Meteorological Condition

Net radiation (R_N) and photosynthetically active radiation (PAR) were measured with a net radiometer (model Q-7, Radiation and Energy Balance Systems, REBS, Seattle, Washington) and a quantum sensor (model 190SB quantum sensor, LI-COR, Inc., Lincoln, Nebraska) at a height of approximately 1.2 m above ground, respectively. Air temperature and relative humidity were determined using an air temperature and relative humidity probe (model HMP45C-L50, Vaisala Inc., Helsinki, Finland) at a height of 3.0 m. Soil heat flux (G) was measured using three soil heat flux plates (model HFT-1, Campbell Scientific Inc., Logan, Utah) buried 2 cm below the moss surface. Soil temperature was measured using type T thermocouples at 0 cm, 5 cm and 10 cm below the ground. Micrometeorological data were scanned at every 1 minute and averaged 30 minutes. The 30 min averaged data were stored using a datalogger (Model 21X, Campbell Scientific Inc., Logan, Utah). Refer the web site below for further instrument description: http://www.sci.sdsu.edu/GCRG/bio354/Instruments/instruments.html

More detailed information such as description, accuracy, and model of the instrumentation are shown in Table 1.

Table 1. Information of instruments used to measure CO₂, water vapor, and meteorological data.
Instrument	Instrument (Model)	Description	Accuracy	Note
3D-Sonic Anemometer	R3	Wind direction and wind speed	Wind Direction: <1% RMS Wind speed: <1% RMS	Wind speed resolution: 0.01m s^-1
Open-Path IRGA	LI-7500	CO₂ , water vapor and pressure		Operating Temperature: -25°C to +50°C
Net Radiometer	Q-7	Net Radiation		Spectral response 0.25 to 60 µm
Quantum Sensor	LI-190SB	Photosynthetically active radiation		Spectral response 0.4 to 0.7 µm
Temperature Sensor	HMP45C	Air Temperature	at 20°C ±0.2 ^oC	Operating Temperature: -40°C to +60°C
Relative Humidity Sensor	HMP45C	Relative Humidity	at 20°C ±2% RH (0 to 90% Relative Humidity) ±3% RH (90 to 100% Relative Humidity)	Operating Temperature: -40°C to +60°C
Soil Temperature Sensor	Type-T Thermocouples	Soil temperature
Ground Heat Flux Sensor	HFT-L50	Soil Heat Flux	±5% of reading	Operating Temperature: -40°C to +55°C

DATA COLLECTION and PROCESSING

See INSTRUMENT DESCRIPTION.

DATA FORMAT

Data Format

Met data: Data format is tab delimited ASCII

Extension of data file is “dat”

Eddy data: Data files are Excel version.

Extension of data file is “xls”

Data File Name and Contents

File Name	Content
*Data*
2000
SewardPen_QuartzCreek_2000_OldTussock_Met.dat	MetDat^† at the old tussock tundra
SewardPen_QuartzCreek_2000_Shrub_Met.dat	MetDat at the shrub tundra
SewardPen_QuartzCreek_2000_YoungTussock_Met.dat	Weather data at the young tussock tundra
SewardPen_QuartzCreek_2000_JD207_YT_Eddy_Reduced.xls	EDat^‡ at the young tussock tundra in JD^§ 207
SewardPen_QuartzCreek_2000_JD208_YT_Eddy_Reduced.xls	EDat at the young tussock tundra in JD 208
SewardPen_QuartzCreek_2000_JD209_YT_Eddy_Reduced.xls	EDat at the young tussock tundra in JD 209
SewardPen_QuartzCreek_2000_JD210_YT_Eddy_Reduced.xls	EDat at the young tussock tundra in JD 210
SewardPen_QuartzCreek_2000_JD211_YT_Eddy_Reduced.xls	EDat at the young tussock tundra in JD 211
SewardPen_QuartzCreek_2000_JD211_S_Eddy_Reduced.xls	EDat at the shrub tundra in JD 211
SewardPen_QuartzCreek_2000_JD212_S_Eddy_Reduced.xls	EDat at the shrub tundra in JD 212
SewardPen_QuartzCreek_2000_JD213_S_Eddy_Reduced.xls	EDat at the shrub tundra in JD 213
SewardPen_QuartzCreek_2000_JD214_S_Eddy_Reduced.xls	EDat at the shrub tundra in JD 214
SewardPen_QuartzCreek_2000_JD215_S_Eddy_Reduced.xls	EDat at the shrub tundra in JD 215
SewardPen_QuartzCreek_2000_JD215_OT_Eddy_Reduced.xls	EDat at the old tussock tundra in JD 215
SewardPen_QuartzCreek_2000_JD216_OT_Eddy_Reduced.xls	EDat at the old tussock tundra in JD 216
SewardPen_QuartzCreek_2000_JD217_OT_Eddy_Reduced.xls	EDat at the old tussock tundra in JD 217
SewardPen_QuartzCreek_2000_JD218_OT_Eddy_Reduced.xls	EDat at the old tussock tundra in JD 218
SewardPen_QuartzCreek_2000_JD219_OT_Eddy_Reduced.xls	EDat at the old tussock tundra in JD 219
2001
SewardPen_QuartzCreek_2001_Met.dat	MetDat at the old tussock tundra
SewardPen_QuartzCreek_2001_JUNE_Eddy_Reduced.xls	EDat at the old tussock tundra in June
SewardPen_QuartzCreek_2001_JULY_Eddy_Reduced.xls	EDat at the old tussock tundra in July
SewardPen_QuartzCreek_2001_AUGUST_Eddy_Reduced.xls	EDat at the old tussock tundra in August

*Report*
NPS_Report_1999_Oechel.pdf	Net ecosystem CO₂ flux of age-specific sub arctic tussock tundra stand following fire
SewardPen_QuartzCreek_2000_Field_Summary.doc	Summary report for the 2001 field research
^† MetDat: Meteorological Data ^‡EDat : Eddy Data ^§ JD : Julian Day

List of Parameters and Units

Eddy Data

Header	Unit	Description
J.Day		Julian Day
Time	(AST)	Time: local standard time
Time	(Dec T)	Time: Decimal Time
Time	(Min)	Time: Total minutes upto the time
W.Dir	(Deg)	Wind Direction
Ave u	(m s-1)	Wind Speed
t	(Ave u'w')	Tau
u*	(m s-1)	Friction Velocity
Air T	(C)	Air temperature calcualted from sonic anemometer
L-CO2	(volts)	CO2 Voltage from the open-path IRGA
L-H2O	(volts)	H2O Voltage from the open-path IRGA
CO2	(mg m-3)	CO2 in mass density
H2O	(mg m-3)	H2O in mass density
ra	(mg m-3)	air density
Ave u'2		Variance of u component of wind
Ave v'2		Variance of v component of wind
Ave w'2		Variance of w component of wind
T var		Variance of temperature
L-CO2 var		Variance of CO2 in voltage
L-H2O var		Variance of H2O in voltage
Ave w'H'		Covariance of w and temperature
L-w'C'		Covariance of w and CO2
L-w'E'		Covariance of w and H2O
# Samples	(n=18000)	Sample number
H	(W m-2)	Uncorrected sensible heat flux
Corr w'H'		Correction portion of sensible heat flux
Corr H	(W m-2)	Corrected sensible heat flu
Raw w'C'	(mg m-2 s-1)	Uncorrected CO2 flux
Raw w'E'	(mg m-2 s-1)	Uncorrected water vapor flux
WPL w'C'	(mg m-2 s-1)	Corrected CO2 flux in mg m-2 s-1
WPL w'C'	(mmol m-2 s-1)	Corrected CO2 flux in mmol m-2 s-1
WPL w'C'	(gC m-2 hr-1)	Corrected carbon flux in gC m-2 hr-1
WPL w'C'	(gC m-2 d-1)	Corrected carbon flux in gC m-2 d-1
3-Bar Flux	(gC m-2 d-1)
	Flux Int.
WPL w'E'	(mg m-2 s-1)	Corrected water vapor flux in mg m-2 s-1
WPL w'E'	(mmol m-2 s-1)	Corrected water vapor flux in mmol m-2 s-1
Le	(W m-2)	Latent hear flux
WPL w'E'	(m s-1)	Corrected water vapor flux in m s-1
ET	(mm d-1)	Evapotranspiration in mm d-1
	ET Int.
Le+H	(W m-2)	Sum of latent heat and sensible heat
Rn-G	(W m-2)	Sume of net radiation and ground heat flux
Rnet WC	(W m-2)	Net radiation
Ave G	(W m-2)	Averaged ground heat flux
Ave Soil T (0 cm)	(oC)	Averaged soil temperature at surface

Meteorological Data

Headers	Unit	Description
Array		Array Number for the program
ID		ID for the measurement site
Year		Year
J. Day		Julian Day
Time		Local Standard Time
Panel_T		Temperature measured from a datalogger
PAR	m m^-2 s^-1	Photosynthetically active radiation
Rnet_Raw	mV	Voltage from Net Radiometer
Rnet_NWC	W m^-2	Net Radiation without wind correction
Rnet_WC	W m^-2	Net Radiation with wind correction
G1	W m^-2	Soil heat Flux 1
G2	W m^-2	Soil heat Flux 2
G3	W m^-2	Soil heat Flux 3
Air T	^oC	Air Temperature
RH	%	Relative Humidity
ST_1 (0)	^oC	Soil temperature at 0 cm
ST_1 (-5)	^oC	Soil temperature at 5 cm
ST_1 (-10)	^oC	Soil temperature at 10 cm
ST_2 (0)	^oC	Soil temperature at 0 cm
ST_2 (-5)	^oC	Soil temperature at 5 cm
ST_2 (-10)	^oC	Soil temperature at 10 cm
Battery	V	Battery Voltage
Note: In the meteorological data file in 2000, a few parameters which had 2 more set of measurements were averaged. The averaged data are indicated with “Ave”: for example, soil temperature at 0 cm is indicated “Ave_ST (0)” and ground heat flux indicated “Ave_G”.

DATA REMARKS:

PI's assessment of the data: all data have been quality-checked.
Missing data periods: blank
Software compatibility: Excel and notepad