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Harvard Forest Data Archive
Photosynthetically Active Radiation in the Clearcut Site at Harvard Forest since 2013Related Publications
- Lead: Christopher Williams
- Investigators: Myroslava Khomik, Richard MacLean
- Contact: Christopher Williams
- Start date: 2013
- End date: 2013
- Status: ongoing
- Location: Prospect Hill Tract (Harvard Forest)
- Latitude: +42.546
- Longitude: -72.174
- Elevation: 403 meter
- Release date: 2015
- EML file: knb-lter-hfr.231.3
- DOI: digital object identifier
- Related links:
- Project Website
- Leaf Gas Exchange in the Clearcut Site at Harvard Forest 2010-2012
- Vegetation Cover in the Clearcut Site at Harvard Forest since 2010
- Study type: short-term measurement, modeling
- Research topic: ecological informatics and modelling; forest-atmosphere exchange; physiological ecology, population dynamics and species interactions
- LTER core area: primary production, disturbance
- Keywords: canopy cover, irradiance, leaves, light, photosynthetically active radiation
The purpose of these measurements was to capture the light attenuation of the canopy throughout the growing season, which can help in determining leaf area/canopy openness at the site. Measurements were done along a 50-m-long transect (one of the ones used for line-intercept vegetation surveys, on the side of the EC-tower). Eight measurement locations were established along the transect, equidistant, and marked with a bright orange flag. Measurements were taken with a LI-COR LI-191 Line quantum sensor (http://www.licor.com/env/products/light/quantum_sensors/), as described below. Before and after measurements along the transect, PAR-readings were taken in an open area (away from canopy cover) either at a log along the access road to the site or up on the fire tower nearby. At each location along the transect, two measurements were taken – one at the ground surface and one at a height of 1.3m (diameter at breast height).
The study site occupies roughly a 200 m x 400 m area (8 ha) near the top of Prospect Hill, within the Harvard Forest Long Term Ecological Research Site.
Measuring Light Interception with the LI-Quantum Bar Sensor
MEASUREMENTS TO BE DONE ON A CLEAR DAY AROUND NOON (i.e. 11:45-12:15pm). Note: Calibration coefficient should read -159.5.
1. Attach the cable and the logger to the bar. (all should be in the black-gun case).
2. Be gentle with the bar-sensor, especially the white-sensor strip – don’t scratch it.
3. Place the bar onto the log out by the main road, in the open. Locate the bar to be parallel with the main road and pointing its tip down the road – away from the tower. This will be our initial measurement of PAR in the open. All measurements after should be at or below this number.
4. Level the bar.
5. Turn on the logger. Make sure it is reading in mircomoles (µmol).
6. Make sure nothing is shading the white-sensor part of the instrument.
7. When ready, press “Ave” and keep the bar level and steady for 15 seconds.
8. The instrument will be measuring PAR over 15 seconds and will return the computed average on the screen.
9. Record that number in the associated log book. Record also the time of the reading.
10. Press “hold” to make the log go back to instant readings.
11. Move onto one of eight measurement points. These are located along transect 2, marked with orange flags (labeled “PAR1- PAR8”, on your left.
12. Take measurements within our forest: (a) One by placing the bar near the ground (facing the same direction and orientation, as was on the log). Level it. Make sure you are not shadowing the bar. Take a reading as in steps 3-7 above. Record that in the log book. Record also the time of your reading. (b) Next bring the bar to your shoulder level (about 1.3 m – DBH – above the ground) and take a reading, as before in point a. This one will tend to be higher compared to the ground reading. (c) Move onto the next flag.
13. Once you’re done with all eight locations, go back to the log in the open, by the road.
14. Take a final reading on the log, as in steps 3-7.
15. Make notes of the cloud conditions and weather in the log book.
16. Transfer data from log book into digital format for storage.
This dataset is released to the public under Creative Commons license CC BY (Attribution). Please keep the designated contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement.
Williams C. 2015. Photosynthetically Active Radiation in the Clearcut Site at Harvard Forest since 2013. Harvard Forest Data Archive: HF231.
hf231-01: par data
- id: unique data identifier
- datetime: date and time when the measurement was taken
- date: date when the measurement was taken
- time: time of day when the measurement was taken (eastern time zone, local time)
- location: whether measurements were taken in the open or along a transect within the forest stand
- location.id: location identification
- par: par measurement in micromoles per mole (unit: dimensionless / missing value: NA)
- open: whether or not the measurement was taken in the open
- 0: measurement was not taken in the open
- 1: measurement was taken in the open
- dbh: whether or not the measurement was taken at a height of
- 0: measurement was not taken at a height of DBH
- 1: measurement was taken at a height of DBH
- ground: whether or not the measurement was taken at the
- 0: the measurement was not taken at the surface/ground
- 1: the measurement was taken at the surface/ground