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Harvard Forest Data Archive


Understory Removal Experiment at Harvard Forest 1956-2018

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  • Lead: Ernest Gould, Audrey Barker Plotkin
  • Investigators: Fulton Rockwell, Craig Lorimer, William Murison, Shelley Potter, Emilio Arias, Saloni Shah
  • Contact: Information Manager
  • Start date: 1956
  • End date: 2018
  • Status: completed
  • Location: Tom Swamp Tract (Harvard Forest)
  • Latitude: +42.495
  • Longitude: -72.195
  • Elevation: 315 meter
  • Taxa: Acer rubrum (red maple), Quercus rubra (red oak)
  • Release date: 2019
  • Revisions:
  • EML file: knb-lter-hfr.313.3
  • DOI: digital object identifier
  • EDI: data package
  • DataONE: data package
  • Related links:
  • Study type: long-term measurement
  • Research topic: large experiments and permanent plot studies; physiological ecology, population dynamics and species interactions
  • LTER core area: primary production, populations
  • Keywords: canopies, competition, diameter at breast height, forest dynamics, tree growth, maple, oak
  • Abstract:

    In 1956, Ernie Gould and colleagues established an experiment to test whether removing understory trees will accelerate the growth of the residual overstory. The motivation for the experiment was the suggestion that the understory uses growth materials that would otherwise be available for the main canopy crop trees, and that if the understory were removed the development of the crop trees would be accelerated.

    In Tom Swamp Compartment I, a 300’ by 400’ rectangular plot was established in a closed-canopy hardwood forest, and every tree >2 inches dbh was mapped, measured and assigned to the overstory or understory. In half of the plot, all understory trees and woody shrubs were cut. Wood and brush were removed from the study area. Sprouts that emerged were killed by spraying with 2-4-5-T and kerosene in 1956 and 1958.

    Diameter growth measurements of the remaining trees (overstory in the treated area; overstory and understory in the control) were repeated in 1960, 1966, 1969, and 1975 as part of the original experiment. The control portion of the plot was measured in 2003 and 2018.

    This data set contains tree measurements from the control portion of the site for 1956, 1969, 1975, 2003, and 2018. Additional measurements are available on paper data sheets in the Harvard Forest Document Archives (Research File HF 1956-03). Results of the understory removal experiment are reported in Kelty and Gould (1987).

  • Methods:

    plot layout

    The long axis of the plot is oriented ~SW-NE, and is 400 feet by 300 feet. It is broken into 48 record-units, each 50x50 feet. There are metal stakes every 50 feet along the perimeter of the plot. The N/S E/W locations are based on a grid established by W. Lyford. See hf313-03-ts-exp56-2-plot-layout.pdf for a diagram of the plot layout.

    For each record-unit, a sketch map included locations and numbers for each tree, which matched measurements of diameter and canopy class. For the purposes of the experiment, understory trees were defined as all those completely overtopped by adjoining trees, plus those with tops of crowns below the mid-point of the live crowns of adjoining overstory trees.

    In 1977, Craig Lorimer coded the data on computer cards, and analyzed the control data as part of an analysis of the red maple understory. In 2003, Fulton Rockwell remeasured the control sections of the plot, and in 2018, Audrey Barker Plotkin led re-measurement of the control sections of the plot.

  • 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:

    Gould E, Barker Plotkin A. 2019. Understory Removal Experiment at Harvard Forest 1956-2018. Harvard Forest Data Archive: HF313 (v.3). Environmental Data Initiative:

Detailed Metadata

hf313-01: tree data

  1. latin.code: scientific abbreviation for species
  2. species: species abbreviation used on field data sheets
  3. unit: record sub-unit of plot
  4. tree number, matches original field maps
  5. dbh1956: diameter at breast height in 1956 (unit: centimeter / missing value: NA)
  6. dbh1969: diameter at breast height in 1969 (unit: centimeter / missing value: NA)
  7. dbh1975: diameter at breast height in 1975 (unit: centimeter / missing value: NA)
  8. dbh2003: diameter at breast height in 2003 (unit: centimeter / missing value: NA)
  9. dbh2018: diameter at breast height in 2018 (unit: centimeter / missing value: NA)
  10. cc1956: crown class in 1956
    • o: overstory
    • u: understory
  11. cc1969: crown class in 1969
    • o: overstory
    • u: understory
  12. cc1975: crown class in 1975
    • o: overstory
    • u: understory
  13. cc2003: crown class in 2003
    • o: overstory
    • u: understory
  14. cc2018: crown class in 2018
    • o: overstory
    • u: understory
  15. cond1956: condition in 1956
    • L: live
  16. cond1969: condition in 1969
    • L: live
    • M: died since last inventory
    • R: recruited, that is, grew into tree-size class since last inventory
  17. cond1975: condition in 1975
    • L: live
    • M: died since last inventory
    • R: recruited, that is, grew into tree-size class since last inventory
  18. cond2003: condition in 2003
    • L: live
    • M: died since last inventory
    • R: recruited, that is, grew into tree-size class since last inventory
    • miss: live in prior and subsequent census, but no measurement information. Therefore, this tree was missed in this year’s inventory.
  19. cond2018: condition in 2018
    • L: live
    • M: died since last inventory
    • R: recruited, that is, grew into tree-size class since last inventory
  20. comments: comments

hf313-02: species codes

  1. common name of species
  2. field.code: abbreviation used on field data sheets
  3. genus and species
  4. latin.code: scientific abbreviation for (first two letters of genus and first two letters of species)

hf313-03: plot layout diagram

  • Compression: none
  • Format: pdf
  • Type: document