Daily summaries of photosynthetically active radiation (PAR), relative humidity, and temperature data logged above, within, and below Betula nana and Salix pulchra shrub canopies during the summer of 2012 in vicinity of Toolik Lake, Alaska.

Abstract: 

This file contains limited daily summaries of PAR, relative humidity, and temperature data monitored above, within, and below Betula nana and Salix pulchra shrub canopies at two locations near Toolik Lake, Alaska during the summer of 2012. The location of the PAR sensor and dataloggers were co-located with the LTER shrub plots (block 1 and 2), also used for the chamber flux and point frame measurements taken this same year. There were two logging sites (block 1 and 2), each of which had PAR five PAR sensors, two for each shrub canopy and one above, as well as three sensors to log relative humidity and temperature. This file contains maximum PAR, total daily PAR, and daily average temperature data, as well as intermittant maximum and minimum values for temperature and relative humidity. Data monitored every five minutes is available in the file "ShrubCanopy_InstantLogger".

Project Keywords: 

Data set ID: 

10143

EML revision ID: 

8

Short name: 

2012_GS_ITEX_ShrubCanopy_DailyLogger
People

Keywords: 

Arctic LTER keywords: 

Taxa: 

Dates

Date Range: 

Saturday, June 23, 2012 to Tuesday, August 14, 2012

Publication Date: 

Wednesday, December 12, 2012

Methods: 

Automated Data Logging
In order to monitor canopy conditions of the shrub species of interest--Betula nana and Salix pulchra--two CR1000 dataloggers (Campbell Scientific, 815 W. 1800, North Logan, UT, USA) were installed at the sites used for the ITEX shrub canopy studies at Toolik Field Station in Alaska the summer of 2012. The sites (see "Group" category) are labeled as "Upland" and "Outlet"--descriptions of the sample site in relation to Toolik Lake. The Upland site is colocated with Block 1 of the LTER shrub vegetation plots; the Outlet site is colocated with Block 2. The dataloggers were adjacent to, rather than within, LTER plots.

Both the Upland and Outlet datalogger had the following sensors which logged every five minutes:
(5) Photosynthetically active radiation (PAR) sensors: LI-190SB Quantum Sensor (Li-Cor Biosciences, 4647 Superior St, Lincoln, NE, USA)
* Sensors were placed as follows: (1) Above all vegetation at a height of 2.2 meters
(1) Mid-way within the B. nana canopies (approximately 40 cm above the soil)
(1) Mid-way within the S. pulchra canopies (approximately 40 cm above the soil)
(1) Below the B. nana canopies (approximately 10 cm above the soil)
(1) Below the S. pulchra canopies (approximately 10 cm above the soil)

(3) Relative humidity (RH) and temperature sensors: HMP50/HMP60 Probe (Campbell Scientific, North Logan, UT, USA)
* Sensors each had either a 6- or 10-plate radiation shield (Campbell Scientific model 41303-5A or 41003-5)
* Sensors were placed as follows: (1) Above all vegetation at a height of 2 meters
(1) Below the B. nana canopies (approximately 10 cm above the soil)
(1) Below the S. pulchra canopies (approximately 10 cm above the soil)

These instantaneous data are available in the file "Instant_Logger". The extreme values that sensors encountered were also recorded; these are included in this file.

The temperature monitoring performed by the datalogger itself (maximum and average daily temperatures) do not represent direct air temperatures as the datalogger was housed in a sealed, white, hard-plastic box mounted approximately 1.5 meters above the ground.

SunScan LAI and PAR Measurements:
As with other measurments collected the summer 2012 for the ITEX project at Toolik Field Station, a Delta-T SunScan wand (Delta-T Devices Ltd, Burwell Cambridge, UK) was use to characterize the shrub canopies with the dataloggers. These data are included in the datasets: "SunScan_LAI_Data" and "SunScan_PAR_Data". The methods used for each are described below.

The methods used to collect PAR at many heights within each canopy were the same used to collect LAI, with the difference being the setting on the SunScan wand. The measurements were taken near the end of the growing season when leaves were already beginning to senesce. Additionally, while these measurements are traditionally made in conjunction with a Beam Fraction sensor (BF3), this sensor was malfunctioning when the datalogger sites were sampled , and thus it was not used. Instead of the BF3 sensor, wand measurements above the canopy were made immediately prior to each data measurement to record the ambiant total irradiance levels.

Readings were taken by inserting the SunScan wand near to the ground as possible--typically starting at 5 centimeters from the ground (the wand rested atop the moss layer)--and then repeated every 15 cm with the last measurement being above the canopy. Measurements were taken with the field technician opposite the direction of the sun at five locations within the canopy at each height. Five replicates were taken at each height in the canopy immediately surrounding the datalogger sensors; this differs from the ITEX samples which had three replicate scans at each height.

The weather conditions during these measurements were almost uniform cloud cover; thus nearly all of the measurements were taken under "diffuse" light conditions (diffuse light fraction greater than 0.7). The measurements taken with "direct" light conditions were taken on partly cloudy days.

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).

In addition to the LAI values, the Delta-T SunScan instrument gives an output of other variables including: transmitted light, spread among sensors, beam fraction, and zenith angle. These values are further described here:

Transmitted Light: the fraction of incident light that passes through a given canopy. It can refer to Direct, Diffuse, or Total incident light.

Spread: the standard deviation of the 64-PAR sensors on the SunScan wand.

Beam Fraction: the fraction of the Total incident PAR in the Direct beam.

Zenith Angle: the angle between the centre of the sun and the point directly overhead.
Zenith angles are calculated from latitude, longitude, and local time using standard astronomical equations as given in Practical Astronomy. The location used to determine the local zenith angle was: 68° 37' 39" N, Longitude 149° 35' 51" W.

*"ELADP is a way of characterizing the horizontal or vertical tendency of leaves in a canopy." p 37 of SS1 User Manual v2.0 (SunScan Canopy Analysis System, type SS1. Delta-T Devices Ltd. May 19, 2008)

For Delta-T SunScan wand used to measure PAR and LAI:
SS1 User Manual v2.0. Delta-T Devices Ltd., May 19, 2008.

Sites sampled.

Download a comma delimited (csv) or Excel file (includes metadata and data sheets).

Use of the data requires acceptance of the data use policy --> Arctic LTER Data Use Policy

To cite this data set see the citation example on the LTER Network Data Portal page for this data set.

Variables Details

(Variables names are in the first line/row of the CSV file and Excel data sheet.)
YEAR
  • Label: YEAR
  • Definition: year of measurement
  • Type: Date/time
  • Date format: YYYY
  • Missing values:
    • #N/A = Missing or Not Measured
DATE
  • Label: DATE
  • Definition: date of measurement
  • Type: Date/time
  • Date format: dd-mmm-yy
  • Missing values:
    • #N/A = Missing or Not Measured
SITE
  • Label: SITE
  • Definition: Toolik
  • Type: Nominal
  • Missing values: None specified
GROUP
  • Label: GROUP
  • Definition: Measurement location in relation to Toolik Lake LTER Shrub plots; In vicinity of Block1 = Upland, IVO Block 2 = Outlet
  • Type: Nominal
  • Missing values: None specified
CANOPY
  • Label: CANOPY
  • Definition: Canopy sensors monitored; sensors above the canopies monitored ambient conditions for both BET and SALP vegetation
  • Type: Nominal
  • Missing values: None specified
SENSOR POSN
  • Label: SENSOR POSN
  • Definition: Sensor relative height
  • Type: Nominal
  • Missing values: None specified
BattV_Min
  • Label: BattV_Min
  • Definition: Minimum battery voltage during the day of measurement (battery is 12v)
  • Type: Physical quantity
  • Unit: volt
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured
PTemp_C_Max
  • Label: PTemp_C_Max
  • Definition: Maximum temperature (deg Celsius) measured by datalogger
  • Type: Physical quantity
  • Unit: celsius
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured
PTemp_C_TMx
  • Label: PTemp_C_TMx
  • Definition: 24-hour time that the maximum datalogger temperature was recorded
  • Type: Date/time
  • Date format: HH24:Mi
  • Missing values:
    • #N/A = Missing or Not Measured
PTemp_C_Avg
  • Label: PTemp_C_Avg
  • Definition: Daily average temperature encountered by datalogger
  • Type: Physical quantity
  • Unit: celsius
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured
MAX TEMP
  • Label: MAX TEMP
  • Definition: Maximum temperature (deg Celsius) measured by relative humidity sensor for given canopy / position
  • Type: Physical quantity
  • Unit: celsius
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured
TIME OF MAX TEMP
  • Label: TIME OF MAX TEMP
  • Definition: 24-hour time that maximum temperature was encountered
  • Type: Date/time
  • Date format: HH24:Mi
  • Missing values:
    • #N/A = Missing or Not Measured
MIN TEMP
  • Label: MIN TEMP
  • Definition: Minimum temperature (deg Celsius) measured by relative humidity sensor for given canopy / position
  • Type: Physical quantity
  • Unit: celsius
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured
TIME OF MIN TEMP
  • Label: TIME OF MIN TEMP
  • Definition: 24-hour time that minimum temperature was encountered
  • Type: Date/time
  • Date format: HH24:Mi
  • Missing values:
    • #N/A = Missing or Not Measured
MAX RH
  • Label: MAX RH
  • Definition: Maximum recorded relative humidity encountered by given sensor
  • Type: Physical quantity
  • Unit: percent
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured
TIME OF MAX RH
  • Label: TIME OF MAX RH
  • Definition: 24-hour time that maximum relative humidity was encountered
  • Type: Date/time
  • Date format: HH24:Mi
  • Missing values:
    • #N/A = Missing or Not Measured
MAX PAR
  • Label: MAX PAR
  • Definition: Maximum recorded photosynthetic active radiation (PAR) for given sensor (umol PAR per square m per sec)
  • Type: Physical quantity
  • Unit: micromolePerMeterSquaredPerSecond
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured
TIME OF MAX PAR
  • Label: TIME OF MAX PAR
  • Definition: 24-hour time that maximum PAR was encountered by sensor
  • Type: Date/time
  • Date format: HH24:Mi
  • Missing values:
    • #N/A = Missing or Not Measured
DAILY TOTAL PAR
  • Label: DAILY TOTAL PAR
  • Definition: Sum of PAR encountered by given sensor during the day (umol PAR per square m per day)
  • Type: Physical quantity
  • Unit: micromolePerMeterSquaredPerDay
  • Maximum: Not specified
  • Minimum: Not specified
  • Precision: Not specified
  • Missing values:
    • #N/A = Missing or Not Measured