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Harvard Forest Data Archive


Sapwood Temperatures in Hemlock Trees at Harvard Forest HEM Tower 1997-1998

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  • Lead: Julian Hadley
  • Investigators:
  • Contact: Information Manager
  • Start date: 1997
  • End date: 1998
  • Status: complete
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.539 degrees
  • Longitude: -72.180 degrees
  • Elevation: 355 meter
  • Datum: WGS84
  • Taxa: Tsuga canadensis (eastern hemlock)
  • Release date: 2023
  • Language: English
  • EML file: knb-lter-hfr.156.14
  • DOI: digital object identifier
  • EDI: data package
  • DataONE: data package
  • Related links:
  • Study type: short-term measurement
  • Research topic: forest-atmosphere exchange; physiological ecology, population dynamics and species interactions
  • LTER core area: primary production
  • Keywords: plant physiology, temperature, wood
  • Abstract:

    Sapwood temperatures in four large hemlocks, 130-200 years old and about 40 to 90 cm basal diameter and 25 to 29 m tall, were measured in order to estimate sapwood respiration in these trees as part of a physiological model for hemlock forest carbon exchange. As expected, sapwood temperature varied most in small branches and least in the main bole of the tree near the ground. An additional finding from these measurements is that sapwood begins to freeze at -1 to -2 degrees C, as shown by a stabilization and in some cases an increase of about 1 degree C in sapwood temperature when air temperature cooled continuously to below this temperature range.

  • Methods:

    Type T (copper-constantan) thermocouples were made by twisting and then soldering 20 gauge thermocouple wire of this type, supplied by Omega, Stamford, CT, USA. Branches were selected in the upper, middle, and lower canopies of the four trees, on the S, W, N, and E sides of each tree, except that the side of each tree facing the canopy access tower in the middle were not sampled. Thermocouples were inserted either at the midpoint between the branch base and end, or at the furthest point that a person with feet resting on a branch base could reach. In the bole, thermocouples were inserted at 1.25 m above ground, at the level of the lowest live branches (15-18 m above ground), and about 2 m below the top of each tree, on the side of the tree facing the canopy-access tower. Holes 1.5 cm deep were drilled into the sapwood in order to insert the thermocouples. Thermocouples were connected to one of three dataloggers (Model CR10, Campbell Scientific, Logan, UT, USA) on the tower, by type T thermocouple extension wires, between 5 and 15 m long. Sapwood temperatures at each location was measured every 60 seconds, and an average calculated once per hour. Air temperature was measured and averaged at the same frequency, using a shaded 20-gauge thermocouple 22 m above ground, about midway the levels of upper- and mid-canopy sapwood thermocouples.

  • Organization: Harvard Forest. 324 North Main Street, Petersham, MA 01366, USA. Phone (978) 724-3302. Fax (978) 724-3595.

  • Project: The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts. (ROR).

  • Funding: National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210.

  • Use: This dataset is released to the public under Creative Commons CC0 1.0 (No Rights Reserved). Please keep the dataset creators informed of any plans to use the dataset. Consultation with the original investigators is strongly encouraged. Publications and data products that make use of the dataset should include proper acknowledgement.

  • License: Creative Commons Zero v1.0 Universal (CC0-1.0)

  • Citation: Hadley J. 2023. Sapwood Temperatures in Hemlock Trees at Harvard Forest HEM Tower 1997-1998. Harvard Forest Data Archive: HF156 (v.14). Environmental Data Initiative:

Detailed Metadata

hf156-01: sapwood temperature

  1. datetime: date and time
  2. year: year
  3. doy: day of year (unit: nominalDay / missing value: NA)
  4. hour: hour at end of measurement interval
  5. ac.tair: above canopy air temperature (unit: celsius / missing value: NA)
  6. tree.num: tree number
  7. location: location on tree
    • UC: upper canopy
    • MC: middle canopy
    • LC: lower conopy
    • LB: lower bole
  8. direction: side of tree from which measurement was taken
    • N: north
    • S: south
    • E: east
    • W: west
  9. sapwood.temp: sapwood temperature (unit: celsius / missing value: NA)