uid=ARC,o=lter,dc=ecoinformatics,dc=org all public read 2012_GS_ITEX_LC_ParameterSummary.04 Arctic LTER Program Gaius Shaver

Ecosystems Center at the Marine Biological Laboratory 7 MBL Street Woods Hole MA 02543 United States

Arctic LTER Program

The Ecosystems Center Marine Biological Lab 7 MBL St Woods Hole MA 02543 USA

(508) 289 7496 arc_im@mbl.edu http://ecosystems.mbl.edu/ARC/ Edward Rastetter

Ecosystems Center at the Marine Biological Laboratory 7 MBL Street Woods Hole MA 02543 United States

Associated Researcher Mathew Williams

University of Edinburgh School of Geosciences Darwin Building Edinburgh EH9 EJU United Kingdom

Associated Researcher James Laundre

Ecosystems Center at the Marine Biological Laboratory 7 MBL Street Woods Hole MA 02543 United States

Data Manager Laura van der Pol

Ecosystems Center at the Marine Biological Laboratory 7 MBL Street Woods Hole MA 02543 United States

Field Crew 2013 14 1m x 1m shrub plots were sampled the summer of 2012 under direct and diffuse light conditions. Light response curves were measured under each light condition for each plot using a Li-Cor 6400 to measure net ecosystem exchange (NEP); these measurements were modelled using a saturatingMichaelis-Menton formula. The best fit parameters for those models are contained here (Pmax, K, RE, Eo, and light compensation point) for each individual NEP light response curve (direct, diffuse, and intermediate light conditions) measured with corresponding NDVI , LAI, diffuse light fraction, and average temperature. Sorting variables and curve ID numbers for each curve match the corresponding data in the flux data file. photosynthesis shrub canopy chamber flux measurement light curve direct light diffuse light fraction Acceptance and utilization of LTER data requires that: The Principal Investigator be sent a notice stating reasons for acquiring any data and a description of the publication intentions. The Principal Investigator of the data set be sent a copy of the report or manuscript prior to submission and be adequately cited in any resultant publications A copy of any resultant publications should be sent to: Principal Investigator Ecosystems Center Marine Biological Laboratory Woods Hole, MA 02543 http://ecosystems.mbl.edu/ARC/meta_template.php?FileName=./terrest/tracegas/xlsfiles/2012_GS_ITEX_LC_ParameterSummary.html Upland site; co-located in Block 1 of the Shrub LTER sites; IVO 68° 38'18.8" N | 149° 34' 07.2" W +/- 50m. Except for plots marked "FERT" | plots are outside of the designated LTER treatments | though are exposed to the same environmental conditions. All plots were chosen by the dominant shrub canopy (either Salix pulchraor Betula nana) and preferentially selected to be 90cm+ in height. -149.568666666666 -149.568666666666 68.6385555555555 68.6385555555555 Outlet site; co-located in Block 2 of the Shrub LTER sites; IVO 68° 38'008.1" N | 149° 35' 017.1" W +/- 50m. Except for plots marked "FERT" | plots are outside of the designated LTER treatments | though are exposed to the same environmental conditions. All plots were chosen by the dominant shrub canopy (either Salix pulchraor Betula nana) and preferentially selected to be 90cm+ in height. -149.588083333333 -149.588083333333 68.6355833333333 68.6355833333333 2012-06-23 2012-08-07 Organisms Studied Genus Betula Species nana Genus Salix Species pulchra Genus Salix Species glauca This was a season-long project | though it followed similar methods to ITEX projects performed starting in 2003 that are likely to be replicated in the future for reasearch at the Toolik Field Station, AK. Version 2: Missing values changed to #N/A. CH 28Jan2013 Version 3: Updated metadata to newer form (with sites sheet) CH April 2013. Version 4: Corrected the extension of the eml Excel file - it was saved as .xls instead of .xlsx JimL 17May13 Data Manager

The Ecosystems Center Marine Biological Lab 7 MBL St Woods Hole MA 02543 USA

(508) 289 7496 arc_im@mbl.edu http://ecosystems.mbl.edu/ARC/ ARC LTER

The Ecosystems Center Marine Biological Lab 7 MBL St Woods Hole MA 02543 USA

(508) 289 7496 arc_im@mbl.edu http://ecosystems.mbl.edu/ARC/ CHAMBER FLUX MEASUREMENTS CO2 and H2O fluxes were measured using a Licor 6400 photosynthesis system (Li-Cor Inc., Lincoln, Nebraska, USA) connected to a 1m x 1m plexiglass chamber in canopies dominated either by Salix pulchra or Betula nana shrub species. The height of the chamber varied depending on the height of the canopy being measured; chamber bases were constructed of PVC pipe to accomodate canopies with heights up to 125 cm. In addition to the plexiglass chamber, we also constructed a plexiglass "sleeve" that could extend the height of the rigid portion of the chamber by 0.25m. To set up each chamber, a location was chosen where the base would be level enough to ensure a complete seal with the plexiglass chamber and shrub branches could be moved either in or out of the chamber without creating large gaps in the canopy inside the chamber. Branches were included within the chamber if they were rooted within the chamber and excluded otherwise. Once the base was in place, we drove hollow PVC pipe legs into the permafrost and inserted an aluminum frame with foam campermount tape along the top edge for the plexiglass chamber and/or sleeve to rest upon, creating an airtight seal. The aluminum frame had taped to it semi-transparent, plastic skirt which extended to the ground (+30cm). We sealed the skirt to the tundra by weighting the skirt with heavy chains, pushing them firmly into the moss layer where possible and adding additional plastic materials as needed to ensure a good seal. We screwed the LiCor custom chamber head attachment over the holes drilled into the plexiglass chamber, again sealing with a rubber gasket. The air in the chamber was mixed using 4-8 small fans (depending on chamber height) powered by a 12v battery. At each plot we took measurements to create two light curves: one under direct light and one under diffuse light conditions. In order to determine the fraction of diffuse light, we used a DeltaT Beam Fraction Sensor (BF3, Delta-T Devices Ltd, Burwell Cambridge, UK) which quantifies the total irradianc and total diffuse light from which the diffuse light fraction (diffuse light/total light) can be calculated. For each day of flux measurements, the BF3 logged an instantaneous reading every 30-60 seconds set up on a leveled tripod at approximately 2 m above the ground. For the purpose of correlating the diffuse light fraction with each flux measurement, the LiCor 6400 and BF3 sensor were synchronized to read the same time (+/- 1 sec) at the start of each day. Different light levels for both diffuse and direct light curves were achieved by taking measurements under a variety of conditions: ambient light (no manipulation), successive shading levels (covering the chamber with 1-5 fine mesh net cloths), and intercepting direct light with photographic diffuser panels, as well as reflecting light into the chamber to increase the amount of diffuse light with white photographic panels. When the diffuser panels were used, they were carefully positioned to intercept all direct light that would otherwise enter the chamber. Whenwhite reflector panels were used, they were positioned on the side of the chamber opposite the sun and angled towards the chamber so as to increase the amount of diffuse light entering the chamber (these were used in conjuction with the diffuser panels). For these 'artificial' diffuse light measurements, we did not diffuse the BF3 sensor, thus the diffuse fraction calculations during these flux measurements do not represent the light conditions in the chamber. After field tests of using the diffuser and reflector panels, we determined that the panels effectively block all direct light, and thus we assume the diffuse light fraction is greater than 0.7 for these measurements. At each light level a flux measurement lasted 45 - 60 secs in total, with CO2 and H2O concentrations in the chamber recorded by the LiCor 6400 every 2 secs. After each measurement we lifted the chamber until CO2 and H2O concentrations had stabilized at ambient levels. We made an effort to obtain a wide range of flux measurements for light levels between 0-1600, and used whatever chamber light treatments were needed to achieve that based on the ambient light conditions. In addition to light measurements, we made at least three measurements in the dark for each day we took flux measurements. These were achieved by covering the chamber in an opaque tarpaulin cloth. These measurements represent the ecosystem respiration. After each light curve we determined chamber volume by taking depth measurements from the top of the chamber base to the ground. We measured the chamber base depth with 36 measurements made at regular 20cm intervals determined by placing a 1m x1m plastic frame with a 20cm x 20cm string grid on top of the base. The volume determined by these depth measurements (chamber surface area*average depth) was added to the volume of the plexiglass chamber (and sleeve, as needed) . The surface area of the inside of the 1 m x 1 m plexiglass chamber was 0.8836m2. For measurements with a linear change in CO2 (r2>0.97), NEP is calculated from the last 45 seconds of the measurement. [The first 12 seconds of data were always discarded as the LiCor 6400 bases its flux calculations on 10sec averages.] When abnormalities in CO2 slope were observed due to leaks, very small changes in CO2, or changes in light levels, certain portions of the measurement were discaded. CO2 slope was always taken from contiguous data points (i.e. points were never removed from the middle of the measurement period). Often at low light levels near the light compensation point, very small changes in CO2 resulted in measurements within the detection limits of the LiCor 6400, and large segments of the measurement had to be discarded to use a representative, linear segment of the data. All other variablels (H2O flux, pressure, chamber air temperature, CO2 concentration, PAR, PAR range) are calculated over the same time window as NEP. These variables were computed as the average over the course of the measurement. Each flux measurement was placed in one of four categories: direct, diffuse, intermediate, or respiration. These categories are defined as follows: Direct (sunny measurements): diffuse light fraction < 0.40 Diffuse (cloudy or diffused-light): diffuse light fraction > 0.70 Intermediate (partial sun/cloud): 0.40 < diffuse light fraction < 0.70 Respiration (dark): measurements taken in complete darkness; used for all light curve calculations NDVI UNISPEC DATA We measured NDVI on each flux a single channel Unipec spectral analysis system (PP Systems Inc, Amesbury, MA, USA). The unispec spectral analyser measures reflected light intensity in 256 portions of the visible spectrum from ~300nm to ~1100nm. A foreoptic cable transmits light reflected from the target to the instrument, a measurement scan lasts for ~10ms. Nine scans were measured in a regular grid for each of the flux plots. The end of the fibre optic was kept approximately 30cm vertically above the top of the canopy. The NDVI values were calculated using the equation below and then the NDVI values averaged together for each of the nine scans. Each scan was corrected for both incident radiation as well as sensor error. The incident radiation was accounted fo with a "reference scan" taken by holding the foreoptic cable vertically above a white, reference standard under the same light conditions as subsequent measurements. The scans were also corrected for with a "dark scan" taken with the sensor exposed to complete darkness (covering the sensor input with a black cloth) to account for the intrinsic error in the sensor itself. The program Multispec5.1.5.exe was used to compile and integrate the Unispec reflectance spectra from the raw target spectra. CHAMBER LIGHT RESPONSE CURVES The net ecocystem photosynthesis rate (NEP) was estimated by modelling the chamber flux measurements for each plot under direct and diffuse light with a saturating (michaelis-Menton type) function fitted to the measured data. Best-fit parameters are calcuated by minimising the sum of the squared errors between measured and modeled NEP values, using the Excel sover add-in. This model was run separately for each light curve, thus each chamber has a diffuse light curve, a direct light curve, and some have a so-called "intermediate" light curve if there were a substantial number of measurements taken that were under diffuse fraction conditions greater than 0.40 but less than 0.70. The model equation and parameters are described below. LAI SUNSCAN DATA The methods used to collect leaf area index (LAI) estimates at many heights within each canopy were the same used to collect PAR (see "SunScan_PAR_Data"). We measured the LAI using a DeltaT SunScan wand in conjuction with the BF3 sensor (Delta-T Devices Ltd, Burwell Cambridge, UK). The SunScan wand compares indident light readings measured on the BF3 sensor with the 64-PAR readings on the light wand to calculate LAI along the length of the 1m-long wand. LAI was measured by inserting the SunScan wand as near to the ground as possible--typically ~5cm from the ground as the wand rested on top of moss--and then measured vertically every 15 cm with the last measurement being above the canopy. Measurements were taken from the side of the chamber or point frame opposite the sun at three locations under both direct (ambient) and diffuse light conditions . In many cases the replicates at each height were differentiated by row (1-3, or occasionaly 3-8 which correspond to the point frame pins). Typically diffuse light conditions were achieved by shading both the BF3 sensor and the shrub canopy with photographic diffuser panels. On occasion, measurements were taken during cloudy light conditions where the diffuse light fraction was greater than 0.7 and no diffuser panel was needed; on these occasions the direct and diffuse light estimates may have been taken in slightly different locations as they were taken at different times and the precise position of the SunScan wand could not be replicated exactly. The SunScan wand measures PAR along 64 points along a 1-m horizontal profile. When sampling PAR within the shrub canopy, the data are from the raw output from each PAR sensor. When sampling LAI, there is an internal calculation performed though the Delta-T software that compares the reading above the canopy to the reading within the canopy, and takes into account the percent of absorbed PAR (assumed to be 0.85), and the ellipsoidal leaf angle distribution parameter (ELADP*) (assumed to be 1.0). While the LAI data from each height in the chamber flux canopies are available, the data here are only from the lowest, ground-level measurements (~5cm) to represent the canopy LAI. CALCULATIONS: INDIVIDUAL FLUX MEASUREMENTS: Fluxes are calculated from the slope of chamber CO2 (umol mol-1) [or H2O (mmol mol-1)] concentration against time. NEP = rho x vol x dCdry/dt rho = P_av x 1000 SA R T where NEP = net CO2 flux [umol m-2 s-1] rho = air density [mol/m3] P_av = pressure [kPa] R = ideal gas consant 8.314 [J mol K-1] T = temperature [K] = Temp_av [0c] + 273. vol = chamber volume {m3} dCdry/dt = slope of chamber water-dilution-corrected CO2 conc against time [umol mol-1 s-1] SA = chamber surface area [m2] = 0.8836 For net fluxes, a negative flux represents CO2 uptake by vegetation, a positive flux represents CO2 loss from the ecosystem to the atmosphere. RE = NEP during dark measurement GEP = RE - NEP LIGHT RESPONSE CURVE MODEL: Light response curves are modeled as: NEP = Re - Pmax*PAR K + PAR where Re = ecosystem respiration [µmol C m-2 ground s-1] Pmax = light saturated ecosystem photosynthesis [µmol C m-2 ground s-1] K = half saturation constant [µmol PAR m-2 ground s-1] E0 = ecosystem light use efficiency [µmol C µmol-1 PAR] LCP = ecosystem light compensation point [µmol PAR m-2 ground s-1] The initial slope of the light response curve (light use efficiency or E0), the light compensation point (LCP), and the gross primary productivty at a PPFD of 600 µmol m-2 s-1 (or GPP600) are calculated from these parameters as: E0 =Pmax/K LCP = RE*K Pmax-RE GPP600 = Pmax*600 K + 600 The 'Avg time of measurement' was calculated in Excel by converting the time of each flux measurement to a decimal, averaging the decimal-time values in a Pivot table, and then changing the averaged value format back into the HH:MM:SS format contained here. The respiration measurement times were not included in these averages, nor were they included in the average chamber air temperature. NDVI FROM UNISPEC NDVI = (RII-RI) (RI + RII) where RI = average reflectance from 570nm to 680nm RII = average reflectance from 725nm to 1000nm. REFERENCE: ITEX Manual, as updated in 2011 pers-1 ITEX Manual, as updated in 2011 Gus Shaver

The Ecosystems Center Marine Biological Lab 7 MBL St Woods Hole MA 02543 USA

(508) 289 7496 gshaver@mbl.edu Lead PI Jim Laundre

The Ecosystems Center Marine Biological Lab 7 MBL St Woods Hole MA 02543 USA

(508) 289 7496 arc_imr@mbl.edu Information Manager The goal of Arctic LTER project is to predict the future ecological characteristics of the site based upon our knowledge of the controls of ecosystem structure and function as exerted by physical setting and geologic factors, climatic factors, biotic factors, and the changes in fluxes of water and materials from land to water. To achieve this goal the Arctic LTER uses several approaches: Long-term monitoring and surveys of natural variation of ecosystem characteristics in space and time. Includes: climate, plant communities and productivity, thaw depth, stream flow, chemistry of streams and lakes, temperatures of streams and lakes, lake chlorophyll lake productivity, zooplankton abundance. Experimental manipulation of ecosystems for years and decades. Includes: tundra warming, shading, and fertilizing, grazer exclusions, fertilization of lakes and streams, addition and subtraction of predators. Synthesis of results and predictive modeling at ecosystem and watershed scales. Includes: stream N cycling, lake physics, bioenergetics of fish populations, water movement and transfer of DOC and nutrients from land to water, soil respiration, cycling and storage of C in tundra under different scenarios of future climates. This material is based upon work supported by the National Science Foundation under Grants #DEB-981022, 9211775, 8702328; #OPP-9911278, 9911681, 9732281, 9615411, 9615563, 9615942, 9615949, 9400722, 9415411, 9318529; #BSR 9019055, 8806635, 8507493. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The Arctic LTER research site (68°N and 149°W) is in the foothills region of the North Slope of Alaska and includes the entire Toolik Lake watershed and the adjacent watershed of the upper Kuparuk River, down to the confluence of these two watersheds. This area is typical of the northern foothills of the Brooks Range, with continuous permafrost, no trees, a complete snow cover for 7 to 9 months, winter ice cover on lakes, streams, and ocean, and cessation of river flow during the winter. Tussock tundra vegetation of sedges and grasses mixed with dwarf birch and low willows form the dominant vegetation type with areas of drier heath tundra on ridge tops and other well-drained sites as well as areas of river-bottom willow communities. -149.75 -149.0433 68.8 68.5 610 1360 meter 2012_GS_ITEX_LC_ParameterSummary.csv Summary of measured and modeled light curve parameters for diffuse, direct, and intermediate light curves for 14 whole-canopy 1mx1m plots sampled near the shrub LTER sites at Toolik Field Station, Alaska, summer 2012. 2012_GS_ITEX_LC_ParameterSummary.csv 1 \r\n column , " http://metacat.lternet.edu/das/dataAccessServlet?docid=knb-lter-arc.10150&urlTail=terrest/tracegas/data/2012_GS_ITEX_LC_ParameterSummary.csv YEAR YEAR year of measurement yyyy #N/A Missing or Not Measured DATE DATE date of measurement dd-mon-yy #N/A Missing or Not Measured SITE SITE Toolik Toolik GROUP GROUP Measurement location in relation to Toolik Lake LTER Shrub plots; In vicinity of Block1 =Upland, IVO Block 2 =Outlet Measurement location in relation to Toolik Lake LTER Shrub plots; In vicinity of Block1 =Upland, IVO Block 2 =Outlet PLOT PLOT Individual plot identifier Individual plot identifier TREAT TREAT none or fertilised annually (FERT) (with N and P) none or fertilised annually (FERT) (with N and P) PLOT SIZE PLOT SIZE 1m x 1m chamber size 1m x 1m chamber size PHASE PHASE Measurement series (round of measurements within each year) ; not used in this dataset number real #N/A Missing or Not Measured CURVE ID CURVE ID Light curve identifier Light curve identifier AVG TIME OF MEASUREMENT AVG TIME OF MEASUREMENT avg time light curve taken hh24:mi:ss #N/A Missing or Not Measured NDVI NDVI NDVI of flux plot dimensionless real #N/A Missing or Not Measured Pmax Pmax light saturated photosynthesis (umol PAR per meter squared ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured K K half saturation constant (umol PAR per umol CO2) micromolePerMicromole real #N/A Missing or Not Measured AVG Measured Re AVG Measured Re measured ecosystem respiration (umol CO2 per meter square ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured Eo Eo ecosystem light use efficiency (umol CO2 per umol PAR) micromolePerMicromole real #N/A Missing or Not Measured LCP LCP ecosystem light compensation point (umol PAR per meter squared ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured AVG CH AIRTEMP AVG CH AIRTEMP average chamber air temp during measurment (deg Celsius) celsius real #N/A Missing or Not Measured MAX PAR MAX PAR maximum ambient PAR at which a flux measurement is taken for that light curve (umol PAR per meter squared per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured GPP600 GPP600 Gross primary productivity at a PPFD of 600 µmol m-2 s-1 (umol CO2 per meter squared ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured AVG BF3 TOT IRRAD AVG BF3 TOT IRRAD Average total irradiation measured with DeltaT Beam Fraction sensor (umol PAR per meter squared ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured AVG BF3 DIFFUSE IRRAD AVG BF3 DIFFUSE IRRAD Average total diffuse light measured with DeltaT Beam Fraction sensor (umol diffuse PAR per meter squared ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured AVG DIRECT:DIFFUSE LIGHT FRACTION AVG DIRECT:DIFFUSE LIGHT FRACTION Average diffuse light divided by total irradiance (umol diffuse PAR per umol total PAR) micromolePerMicromole real #N/A Missing or Not Measured STDEV BF3 TOT IRRAD STDEV BF3 TOT IRRAD Standard deviation of total irradiation measured with DeltaT Beam Fraction sensor (umol PAR per meter squared ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured STDEV BF3 DIFFUSE IRRAD STDEV BF3 DIFFUSE IRRAD Standard deviation total diffuse light measured with DeltaT Beam Fraction sensor (umol diffuse PAR per meter squared ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured STDEV DIRECT:DIFFUSE LIGHT FRACTION STDEV DIRECT:DIFFUSE LIGHT FRACTION Standard deviation diffuse light divided by total irradiance (umol diffuse PAR per umol total PAR) micromolePerMicromole real #N/A Missing or Not Measured DOM VEG DOM VEG Dominant canopy vegetation Dominant canopy vegetation DIRECT LAI-5cm DIRECT LAI-5cm LAI estimate taken under DIRECT light at 5cm from ground (squared meter leaf per square meter ground) meterSquaredPerMeterSquared real #N/A Missing or Not Measured DIFFUSE LAI-5cm DIFFUSE LAI-5cm LAI estimate taken under DIFFUSE light at 5cm from ground (squared meter leaf per square meter ground) meterSquaredPerMeterSquared real #N/A Missing or Not Measured AVG Modeled Re AVG Modeled Re modelled ecosystem respiration (umol CO2 per square meter ground per second) micromolePerMeterSquaredPerSecond real #N/A Missing or Not Measured COMMENTS COMMENTS Comments on NDVI/Unispec measurements Comments on NDVI/Unispec measurements 34 2012_GS_ITEX_LC_ParameterSummary.xlsx An excel file that has worksheets with the metadata and data. 2012_GS_ITEX_LC_ParameterSummary.xlsx Microsoft Excel http://metacat.lternet.edu/das/dataAccessServlet?docid=knb-lter-arc.10150&urlTail=terrest/tracegas/xlsfiles/2012_GS_ITEX_LC_ParameterSummary.xlsx Microsoft Excel file micro Einsteins (1E-06 moles of photons) per square meter per second (radiant flux density) micromoles of substance per micromole Leaf area in square meter per square meter of ground