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Harvard Forest Data Archive


Sap Flow in Red Maple and Red Oak in the Harvard Forest Snow Removal Study 2011

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  • Lead: Pamela Templer
  • Investigators: Jamie Harrison, Andrew Reinmann, Annie Socci-Maloney, Nathan Phillips, Stephanie Juice, Alex Webster
  • Contact: Information Manager
  • Start date: 2011
  • End date: 2011
  • Status: completed
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.5335 to +42.5368
  • Longitude: -72.1762 to -72.1729
  • Elevation: 1089 to 1197 meter
  • Taxa: Acer rubrum (red maple), Quercus rubra (red oak)
  • Release date: 2020
  • Revisions:
  • EML file: knb-lter-hfr.338.2
  • DOI: digital object identifier
  • EDI: data package
  • DataONE: data package
  • Related links:
  • Study type: short-term measurements
  • Research topic: large experiments and permanent plot studies; physiological ecology, population dynamics and species interactions; regional studies
  • LTER core area: disturbance
  • Keywords: climate change, fine roots, frost, maple, oak, snow, transpiration, water
  • Abstract:

    The climate is changing in mid and high latitude environments with the depth and duration of snowpack shrinking for many temperate forest ecosystems. A reduced snowpack and increased depth and duration of soil frost can injure fine roots, which are essential for plant water uptake. Water uptake is a crucial component of ecosystem functioning because this process strongly impacts other biological processes, such as primary productivity and nutrient uptake. We evaluated the effects of changing winter climate, including snow and soil frost dynamics, on rates of water uptake (i.e. sap flow) in a snow manipulation study at Harvard Forest. We had three reference and tree plots from which we removed snow and induced soil freezing.

  • Methods:

    We used a constant heat-flow method (Granier 1987; Lu et al. 2004) consisting of thermal dissipation probes installed at ~1.4 m height in the bole of each tree. Sap flow sensors were installed at Harvard Forest in May 2011 (before leaf-out; n = 3 sensors per tree, evenly distributed around the bole of the tree; n = 10 trees in reference plots and n = 12 trees in snow removal plots) and left in place until late September in 2010. We evaluated two red oak and two red maple trees in each of six plots (3 reference and 3 snow-removal plots). Each sap flow sensor consisted of two fine-wire copper constantan probes which formed a thermocouple joined at the constantan leads to determine the temperature difference (∆T) between the thermocouples as influenced by rates of sap flow. Bark was chiseled from each sensor’s location to expose the sapwood, then sensors were installed in freshly drilled holes extending 21 mm into the sapwood. The heated sensor within each thermocouple had electrically insulated constantan heating wire coiled around its length, was coated with thermally conducting silicon grease, and installed in the sapwood inside of an aluminum cylinder. Each heated sensor was oriented in the sapwood approximately 10 cm above an unheated reference probe and received 200 mW power. Once installed, sap flow sensors were covered with a plastic housing affixed to the tree with acid-free silicon sealant to prevent stem flow from reaching them. To minimize temperature fluctuations due to direct solar heating, sap flow sensors were tented with Reflectix (Markleville, IN) aluminum insulated wrap. Temperatures were recorded at 30 s intervals, and 30 min averages were recorded on multichannel dataloggers (Campbell Scientific CR1000 with AM16/32 multiplexers). Sap flow per unit area sapwood per second (Js, in g H2O m-2 sapwood area s-1) was calculated using an empirical calibration equation by Granier (1987).

    Granier A. 1987. Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements. Tree Physiology 3:309–20.

    Lu P, Urban L, Zhao P. 2004. Granier’s thermal dissipation probe TDP method for measuring sap flow in trees: theory and practice. Acta Botanica Sinica-English Edition 466:631–46.

  • 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.

  • Citation:

    Templer P. 2020. Sap Flow in Red Maple and Red Oak in the Harvard Forest Snow Removal Study 2011. Harvard Forest Data Archive: HF338 (v.2). Environmental Data Initiative:

Detailed Metadata

hf338-01: sap flow

  1. datetime: date and time of sample collection
  2. doy: day of year (unit: number / missing value: NA)
  3. year: year of sample collection
  4. time: time of sample collection in EST with daylight savings observed (hhmm) (unit: number / missing value: NA)
  5. plot: plot identifier
  6. treatment: treatment type representing ambient snow conditions or snow removal
    • Reference: ambient snow conditions
    • Treatment: snow removal
  7. tree: tree identifier
  8. species: species type
  9. instantaneous sap flow in grams of water per square meter of sapwood per second (unit: gramsPerMeterSquaredPerSecond / missing value: NA)