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Harvard Forest Data Archive


Leaf and Flower Phenology of Woody Plant Species at Harvard Forest and Southern Quebec 2015

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  • Lead: Dan Flynn, Elizabeth Wolkovich
  • Investigators: Jehane Samaha, Timothy Savas
  • Contact: Information Manager
  • Start date: 2015
  • End date: 2015
  • Status: completed
  • Location: Harvard Forest, Quebec
  • Latitude: +42.46 to +46.00
  • Longitude: -74.02 to 71.05
  • Elevation: 266 to 505 meter
  • Taxa: Acer pensylvanicum (striped maple), Acer rubrum (red maple), Acer saccharum (sugar maple), Alnus incana (speckled alder), Alnus incana subsp. rugosa (speckled alder), Aronia melanocarpa (black chokecherry), Betula alleghaniensis (yellow birch), Betula lenta (cherry birch), Betula papyrifera (paper birch), Corylus cornuta (beaked hazelnut), Fagus grandifolia (beech), Fraxinus nigra (black ash), Hamamelis virginiana (witch hazel), Ilex mucronatus (mountain holly), Kalmia angustifolia (sheep laurel), Lonicera canadensis (american honeysuckle), Lyonia ligustrina (maleberry), Nyssa sylvatica (black gum), Populus grandidentata (big-toothed aspen), Prunus pensylvanica (pin cherry), Quercus alba (white oak), Quercus rubra (red oak), Quercus velutina (black oak), Rhamnus frangula (buckthorn), Rhododendron prinophyllum (early azalea), Spiraea alba (white meadowsweet), Vaccinium myrtilloides (velvet-leaved blueberry), Viburnum cassinoides (witherod), Viburnum lantanoides (hobblebush)
  • Release date: 2019
  • Revisions:
  • EML file: knb-lter-hfr.314.3
  • DOI: digital object identifier
  • EDI: data package
  • DataONE: data package
  • Related links:
  • Study type: short-term measurement
  • Research topic: biodiversity studies; large experiments and permanent plot studies; physiological ecology, population dynamics and species interactions; regional studies
  • LTER core area: populations
  • Keywords: bud burst, flowering, phenology, plant growth, plant species, seasonality, wood
  • Abstract:

    Accurate predictions of spring plant phenology with climate change are critical for projections of growing seasons, plant communities and a number of ecosystem services, including carbon storage. Progress towards prediction, however, has been slow because the major cues known to drive phenology – temperature (including winter chilling and spring forcing) and photoperiod – generally covary in nature and may interact, making accurate predictions of plant responses to climate change complex and nonlinear. Alternatively, recent work suggests many species may be dominated by one cue, which would make predictions much simpler.

    Here, we manipulated all three cues across 28 woody species from two North American forests. Study sites were Harvard Forest and St. Hipplolyte, Quebec. Species were selected for this study based on their prevalence at the study sites; 28 species are included in this study. At each site, multiple cuttings of six or more representative individuals were collected. In total, we tracked the phenology of 2,137 cuttings from 275 individual source plants.

    All species responded to all cues examined. Chilling exerted a strong effect, especially on budburst (-15.8 d), with responses to forcing and photoperiod greatest for leafout (-19.1 and -11.2 d, respectively). Interactions between chilling and forcing suggest that each cue may compensate somewhat for the other. Cues varied across species, leading to staggered leafout within each community and supporting the idea that phenology is a critical aspect of species’ temporal niches.

    Our results suggest that predicting the spring phenology of communities will be difficult, as all species we studied could have complex, nonlinear responses to future warming.

  • Methods:

    Field sampling

    Woody plant cuttings were made in January 2015 for 28 species at Harvard Forest (HF, 42.5°N, 72.2°W) and the Station de Biologie des Laurentides in St-Hippolyte, Québec (SH, 45.9°N, 74.0°W). The typical late January temperatures are -3.4 and -22°C, respectively, with daylengths (across the year) ranging from 9 to 15.25 h and 8.5 to 15.75 h. Weather station data from each field site were obtained for calculations of chilling units.

    Species were chosen based on the dominant forest vegetation at each site, aiming to maximize the number of shared species between the two sites. Of the 28 species, at least 19 occurred at both sites. For each species, up to 15 representative healthy, mature individuals with branches accessible by pole pruners from the ground were tagged in late summer and autumn 2014. In winter 2015, six individuals were located at each site and 4–16 cuttings taken from each individual, depending on the size of the individual and number of treatments to be applied. Cuttings were kept cold and transported back to the Arnold Arboretum in Boston (MA, USA).

    Chilling and growth chamber treatments

    Cuttings were placed in growth chambers at the Arnold Arboretum in Erlenmeyer flasks with distilled water; water was changed every 7–10 days. The bases of cuttings were re-cut at each water change under water to prevent callusing. For 11 of the 28 species, sufficient cuttings were obtained from each individual tree to apply the full set of 12 experimental treatments: 2 temperature (20°C : 10°C warm vs 15°C : 5°C cool)× 2 photoperiod (12 vs 8 h)×3 chilling (no additional chilling, additional 30 d at 4°C, or 30 d at 1.5°C) treatments. For the remaining 17 species, sufficient cuttings were obtained only to apply the temperature and photoperiod treatments, without the additional chilling levels. The total number of cuttings for a given species thus ranged from 24 to 144, depending on presence at each site and application of the chilling treatment. Lighting was a combination of halogen incandescent bulbs and T5HO fluorescent lamps with the lamploft adjusted to provide c. 400 lmol m2 s1 as measured by Apogee QSO-A5E quantum PAR light sensors in each chamber (sensor set to the height of the cuttings). Treatments were rotated across chambers every 2 weeks, as was flask position within chamber, to remove any possible effects of chamber or flask position.


    Phenology of the cuttings was assessed using a BBCH scale, modified for use in trees (Finn et al., 2007, Annals of Applied Biology 151: 127–131.), with observations on each of the 2136 cuttings made every 2–3 d for the course of the 82-d experiment, a total of 48 observation days. The phenological stages assessed in the present study are budburst, defined as beginning of sprouting or bud breaking or shoot emergence (code 07 in Finn et al., 2007) and leafout, defined as first leaves unfolded (code 11 in Finn et al., 2007). Additional stages up to flowering and stem elongation also were recorded, and we provide a photographic guide to help visualize stages across species (Savas et al., 2017). In total, we made over 19 320 phenological observations at the cutting level.

  • 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:

    Flynn D, Wolkovich E. 2019. Leaf and Flower Phenology of Woody Plant Species at Harvard Forest and Southern Quebec 2015. Harvard Forest Data Archive: HF314 (v.3). Environmental Data Initiative:

Detailed Metadata

hf314-01: budburst

  1. date: observation date
  2. id: unique identifier for twig
  3. sp: species code, see hf314-04-species-info.csv
  4. rep: twig replicate (unit: number / missing value: NA)
  5. site: site location
    • HF: Harvard Forest
    • SH: St. Hippolyte, Quebec
  6. ind: identifier for the souce individual plant
  7. treatcode: treatment code
    • CS0: cold/short/zero additional chilling
    • CL0: cold/long/zero additional chilling
    • WS0: warm/short/zero additional chilling
    • WL0: warm/long/zero additional chilling
  8. warm: temperature treatment
    • warm: warm temperature treatment
    • cool: cool temperature treatment
  9. photo: photoperiod
    • long: long photoperiod
    • short: short photoperiod
  10. chill: chilling treament
    • chill0: no chilling treatment
  11. gen: genus
  12. term.fl: BBCH phenological stage code for terminal flower, if any
  13. lat.fl: BBCH phenological stage code for lateral flower, if any
  14. term.lf: BBCH phenological stage code for terminal leaf bud
  15. lat.lf: BBCH phenological stage code for lateral leaf bud
  16. comments: additional comments
  17. observer: initials of person who made the observations
  18. day: numeric day of the experiment (unit: number / missing value: NA)
  19. day.chill: numeric day of the experiment, for chill treatment. Day 1 is the day this twig was removed from chilling. (unit: number / missing value: NA)
  20. dayuse: numeric day of the experiment corrected for chill treatment for each twig. Day 1 for a given twig ID is the first day it was removed from chilling. (unit: number / missing value: NA)
  21. tleaf: numeric BBCH phenological stage code for terminal leaf bud after correcting for any special characters in term.lf
  22. lleaf: numeric BBCH phenological stage code for lateral leaf bud, after correcting for any special characters in lat.lf

hf314-02: BBCH phenological stage

  1. bbch.code: BBCH phenological stage code from Finn et al. 2007 Annals of Applied Biology, doi:10.1111/j.1744-7348.2007.00159.x
  2. numeric.bbch.code: simplified numeric BBCH code used in this study
  3. principal.growth.stage: description of the BBCH phenological stage from Finn et al.
  4. principal.growth.stage.description: principal growth stage description from Finn et al.
  5. growth.stage.description: growth stage description from Finn et al.

hf314-03: chambers

  1. chamber: growth chamber identifier
  2. treatment: one of four combinations of cold/warm temperatures and long/short days, and additional chilling treatments
  3. day.start: hour of day lights began in the growth chamber. Chill treatments were dark.
  4. day.end: hour of day the lights went off in the growth chamber
  5. temperature during the "day" period (unit: celsius / missing value: NA)
  6. temp.night: temperature during the "night" period (unit: celsius / missing value: NA)
  7. humidity: humidity set point for treatment chambers (%) (unit: dimensionless / missing value: NA)
  8. co2: CO2 set point for treatment chambers (unit: dimensionless / missing value: NA)

hf314-04: species

  1. species: species full name
  2. genus: genus
  3. sp: specific epithet
  4. code: code used in this study
  5. common: common name, from