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Harvard Forest Data Archive

HF033

Phenology and Vegetation Growth in Prospect Hill Soil Warming Experiment at Harvard Forest 1992-1993

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Data

Overview

  • Lead: Elizabeth Farnsworth, Fakhri Bazzaz
  • Investigators: Sonia Careaga, Juan Nunez-Farfan
  • Contact: Emery Boose
  • Start date: 1992
  • End date: 1993
  • Status: completed
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.54
  • Longitude: -72.18
  • Elevation: 365 meter
  • Taxa: Acer pensylvanicum (striped maple), Acer rubrum (red maple), Amelanchier arborea (shadbush), Aralia nudicaulis (wild sarsaparilla), Castanea dentata (american chestnut), Clintonia borealis (blue-bead lily), Crataegus crus-galli (hawthorn), Dennstaedtia punctilobula (hayscented fern), Fagus grandifolia (beech), Gaultheria procumbens (winterberry), Lycopodium annotinum (stiff clubmoss), Lycopodium obscurum (princess pine), Maianthemum canadense (canada mayflower), Medeola virginiana (indian cucumber), Mitchella repens (partridgeberry), Prunus serotina (black cherry), Quercus alba (white oak), Quercus rubra (red oak), Sorbus americana (american mountain ash), Trientalis borealis (starflower), Uvularia sessilifolia (sessile-leaved bellwort), Vaccinium corymbosum (highbush blueberry), Vaccinium vacillans (lowbush blueberry), Viburnum acerifolium (maple-leaf viburnum), Viburnum lentago (nannyberry)
  • Release date: 2003
  • Revisions:
  • EML file: knb-lter-hfr.33.18
  • DOI: digital object identifier
  • Related links:
  • Study type: short-term measurement
  • Research topic: large experiments and permanent plot studies; physiological ecology, population dynamics and species interactions
  • LTER core area: disturbance
  • Keywords: phenology, plant growth, soil warming
  • Abstract:

    As the mean annual temperature of northeast North America rises as a component of global climatic change, it is important to understand how the predominant vegetation of the region will be affected. Existing experimental and correlative evidence from field sites suggests that temperature rise will significantly modify soil processes, nutrient availability, and plant growth. We investigated the responses of temperate deciduous forest vegetation to artificial soil warming at 20 sampling dates during the 1992 and 1993 growing season. We explored whether soil warming measurably altered growth and the temporal dynamics of leaf and fruit production in 26 species of three contrasting plant growth forms (herbaceous perennials, shrubs, and canopy trees). We hypothesized that soil warming would exert differential effects on emergence, phenology, leaf expansion rates, growth, photosynthesis, and vegetative and sexual reproduction among species, with implications for changing community structure in these forests.

    Timing of leaf emergence and flower production was not affected by treatment in saplings; however, mature trees and shrubs leafed out slightly earlier and in larger numbers in heated plots. Soil warming significantly enhanced relative growth in stem diameters of woody plants, especially shrubs, in 1992. This effect was less pronounced in 1993. Species richness was lower in heated plots than in intact control plots in both years; disturbed but unheated control plots showed the lowest species richness of all plots. Changes in relative abundance of herbaceous species from 1992 to 1993 were not significantly affected by treatment. Rank abundances of species were more stable between years in the heated and disturbance-control plots than in the intact plots. Total density of herbaceous species was highest in heated plots during April and May of both years, reflecting greatly accelerated emergence of two dominant species, Maianthemum canadense and Uvularia sessilifolia, due to heating. Stem densities declined later in the season, however, and were lower in the heated plots than in the intact control plots. Photosynthetic rates of the two dominant herbaceous species were not affected by soil warming.

    Of all life forms, herbaceous species (spring ephemerals) were most sensitive to soil warming. Their early appearance could influence carbon and nitrogen acquisition by later-emerging woody species in these deciduous forests. Early leaf-out in woody shrubs and trees can also influence season-long dynamics of water use and carbon sequestration in forests. Soil warming may select for certain tolerant species and reduce species richness in temperate deciduous forests.

  • Methods:

    Growth and phenology of woody vegetation

    Beginning in April 1992, the spring following initiation of soil warming, all woody individuals between 5 mm and 35 mm basal diameter were identified to species (Table 1) and labelled with numbered plastic tags wrapped around the main stem. A subset of larger trees was also monitored (n=12 in heated and control plots; n=15 in disturbance-control plots). Total sample sizes were 109 woody individuals in control and heated plots, and 115 in disturbance-control plots. In April and September of 1992 and 1993, diameter (± 0.1 mm) was measured at two orthogonal locations at the base of the main stem of each plant, as an index of growth over the season. To obtain mean relative diameter increments from April to September 1992 and 1993, the orthogonal diameter measures at each sampling date were first averaged. Relative increments were then calculated for each year separately as ((AvgDiamSept - AvgDiamApr)/AvgDiamApr). Resulting values were arcsin-square root transformed to equalize variances, and investigated with ANOVA using soil treatment as a fixed factor in a randomized block design.

    At 8 spring-summer sampling dates in 1992 and 13 sampling dates in 1993, the phenological status of each of the marked woody individuals was noted. Individuals were inspected for evidence of leaves and reproductive structures, and placed into 1 of 8 phenological states occurring roughly in chronological order: 1) leaf buds closed; 2) buds opening; 3) new leaves expanding; 4) fully expanded leaves with emerging new leaf pair; 5) reproductive (flowers or fruits present); 6) more than 50 % of leaves changing color; 7) more than 50 % of leaves brown or abscised; 8) all leaves dropped. For statistical analyses, data on the phenology of reproduction and leaf production were considered separately. Percentages of all woody individuals reproducing per quadrat were calculated for each year, in three growth classes: trees (greater than 25 cm basal diameter), saplings ( 25 cm basal diameter), and shrub species. Six values of percent reproductives per treatment per growth class per year were obtained. Individuals on which folivory occurred were recorded. Mortality of labelled individuals was noted.

    In order to quantify average area per leaf and leaf expansion rates throughout the 1992 season, we measured the length of the midrib of at least six randomly chosen leaves per plant, in shrubs and saplings in each plot. Leaf area was calculated subsequently from non-destructive leaf length measures, from quadratic regressions of leaf area on leaf length obtained for a sample of 60 randomly collected leaves from each species (r2 between 0.925 and 0.977).

    Community structure, physiology and population dynamics of herbaceous species

    In each 5 x 5 m plot, a 1 x 1 m subplot was randomly designated for monitoring herbaceous flora (less than 5 mm basal diameter) and tree seedlings (species appear in Table 1). Each subplot was observed from 1992-1993. At all sampling dates, all ramets of each species present in the subplot were counted to determine stem density (per m2). Species richness, diversity and evenness values per plot were derived from these censuses. Diversity was calculated as the Shannon-Weiner index H = - piln(pi) where pi is the proportion of the ith species in each subplot. Evenness was scored as J = H /ln(S) where S = species richness in each subplot (scale of 0 to 1 where 0 indicates disproportionate dominance of a few taxa). As an index of vegetative propagation activity and ramet mortality, relative changes in ramet density from 5 June 1992 to 17 May 1993 (dates of density maxima) were computed as ((Density1993 - Density1993)/(Density1992)). The percentage of individuals in vegetative, flowering, fruiting, and fruit dehiscence phases was also recorded for each species in 1993. For the few ramets that actually reproduced, fruit set was quantified as an index of reproductive output.

    Because the two dominant forest floor herbs, Uvularia sessilifolia L. and Maianthemum canadense Desf. showed accelerated appearance in heated plots (see below), their photosynthetic rates were characterized to investigate whether soil warming was influencing plant metabolism. One ramet per species growing naturally in full sun (more than 600 Em-2s-1) and one growing in shade (less than 300 Em-2s-1) was selected in each subplot (n = 6 ramets/species/light environment/soil treatment; total = 72). In situ photosynthesis measurements were made on one fully expanded leaf per ramet between 10 am and 2 pm (cloudless day), May 22, 1994, using a Li-Cor 6200 Photosynthesis system (Li-Cor, Lincoln, Nebraska, USA) fitted with a 1/4-litre cuvette. Sun and shade ramets were examined to obtain a range of photosynthesis values for each species, and to ensure that treatment effects were not obscured by light limitation.

  • Use:

    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.

  • Citation:

    Farnsworth E, Bazzaz F. 2003. Phenology and Vegetation Growth in Prospect Hill Soil Warming Experiment at Harvard Forest 1992-1993. Harvard Forest Data Archive: HF033.

Detailed Metadata

hf033-01: diameter growth

  1. treat: treatment
    • 1: intact control
    • 2: disturbance control
    • 3: heated
  2. block: block into which treatment fell (6 blocks of each of 3 treatments)
  3. quad: quadrat number (1 through 18)
  4. num: number of each plant in quadrant
  5. species: species
    • aaga: Amelanchier arborea
    • bbhch: Vaccinium vacillans
    • bbhg: Vaccinium corymbosum
    • beech: Fagus grandifolia
    • blach: Prunus serotina
    • chest: Castanea dentata
    • crata: Acer rubrum
    • rm: Acer rubrum
    • ro: Quercus rubra
    • sa: Sorbus americana
    • sm: Acer pensylvanicum
    • vest: Viburnum lentago
    • viac1: Viburnum acerifolium
    • wo: Quercus alba
  6. d1apr23: first stem diameter taken on April 23, 1993 (unit: millimeter / missing value: NA)
  7. d2apr23: second (orthogonal) diameter taken on April 23 (unit: millimeter / missing value: NA)
  8. d1may24: first stem diameter taken on May 24, 1993 (unit: millimeter / missing value: NA)
  9. d2may24: Second (orthogonal) diameter taken on May 24, 1993 (unit: millimeter / missing value: NA)
  10. d1jul9: First stem diameter taken on July 9, 1993 (unit: millimeter / missing value: NA)
  11. d2jul9: Second (orthogonal) diameter taken on July 9, 1993 (unit: millimeter / missing value: NA)
  12. d1sep25: First stem diameter taken on September 25, 1993 (unit: millimeter / missing value: NA)
  13. d2sep25: Second (orthogonal) diameter taken on September 25, 1993 (unit: millimeter / missing value: NA)
  14. aprdavg: mean of the two orthogonal diameters taken in April (unit: millimeter / missing value: NA)
  15. juldavg: mean of the two orthogonal diameters taken in July (unit: millimeter / missing value: NA)
  16. septdavg: mean of the two orthogonal diameters taken in September (unit: millimeter / missing value: NA)
  17. growthaj: relative growth in diameter between April and July=(JulDAvg - AprDAvg)/AprDAvg (unit: millimeter / missing value: NA)
  18. growthjs: relative growth in diameter between July and September (unit: millimeter / missing value: NA)
  19. growthas: relative growth in diameter between April and September (unit: millimeter / missing value: NA)
  20. papr16: phenological status of plant on April 16, 1993
    • 1: leaf buds only present
  21. papr23: phenological status of plant on April 23, 1993
    • 1: leaf buds only present
    • 1.5: leaves just emerging
    • 2: leaves expanding
    • 5: mature leaves and fruits present
  22. pmay2: phenological status of plant on May 2, 1993
    • 1: leaf buds only present
    • 1.5: leaves just emerging
    • 2: leaves expanding
  23. pmay17: phenological status of plant on May 17, 1993
    • 2.5: 50% expanded leaves
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 4.5: mature leaves and flowers present
  24. pmay24: phenological status of plant on May 24, 1993
    • 1.5: leaves just emerging
    • 2.5: 50% expanded leaves
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 4: mature leaves present
    • 4.5: mature leaves and flowers present
    • 5: mature leaves and fruits present
  25. pjun7: phenological status of plant on June 7, 1993
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 5: mature leaves and fruits present
  26. pjul9: phenological status of plant on July 9, 1993
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 4.5: mature leaves and flowers present
    • 5: mature leaves and fruits present
  27. pjul23: phenological status of plant on July 23, 1993
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 4.5: mature leaves and flowers present
    • 5: mature leaves and fruits present
  28. paug11: phenological status of plant on August 11, 1993
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 5: mature leaves and fruits present
  29. psep9: phenological status of plant on September 9, 1993
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 4.5: mature leaves and flowers present
  30. psep25: phenological status of plant on September 25, 1993
    • 3: fully expanded young leaves
    • 3.5: 50% mature leaves
    • 4.5: mature leaves and flowers present
  31. poct23: phenological status of plant on October 23, 1993
    • 7: leaves turned color
    • 8: some leaves abscised
    • 9: all leaves abscised

hf033-02: herbacious plants

  1. quad: quadrat number
  2. block: block number
  3. treat: treatment
    • 1: intact control
    • 2: disturbance control
    • 3: heated
  4. s192: maximal density (number of ramets per square meter) of Maianthemum canadense occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  5. s193: maximal density (number of ramets per square meter) of Maianthemum canadense occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  6. s292: maximal density (number of ramets per square meter) of Uvularia sessilifolia occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  7. s293: maximal density (number of ramets per square meter) of Uvularia sessilifolia occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  8. s492: maximal density (number of ramets per square meter) of Lycopodium obscurum occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  9. s493: maximal density (number of ramets per square meter) of Lycopodium obscurum occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  10. s592: maximal density (number of ramets per square meter) of Lycopodium annotinum occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  11. s593: maximal density (number of ramets per square meter) of Lycopodium annotinum occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  12. s692: maximal density (number of ramets per square meter) of Gaultheria procumbens occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  13. s693: maximal density (number of ramets per square meter) of Gaultheria procumbens occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  14. s792: maximal density (number of ramets per square meter) of Medeola virginiana occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  15. s793: maximal density (number of ramets per square meter) of Medeola virginiana occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  16. s992: maximal density (number of ramets per square meter) of Aralia nudicaulis occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  17. s993: maximal density (number of ramets per square meter) of Aralia nudicaulis occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  18. s1092: maximal density (number of ramets per square meter) of Trientalis borealis occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  19. s1093: maximal density (number of ramets per square meter) of Trientalis borealis occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  20. s1192: maximal density (number of ramets per square meter) of Clintonia borealis occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  21. s1193: maximal density (number of ramets per square meter) of Clintonia borealis occurring in the soil warming plots in 1993 (unit: number / missing value: NA)
  22. s1292: maximal density (number of ramets per square meter) of Dennsteadtia punctilobula occurring in the soil warming plots in 1992 (unit: number / missing value: NA)
  23. s1293: maximal density (number of ramets per square meter) of Dennsteadtia punctilobula occurring in the soil warming plots in 1993 (unit: number / missing value: NA)

hf033-03: photosynthetic rates

  1. quad: quadrat number
  2. treat: treatment
    • 1: intact control
    • 2: disturbance control
    • 3: heated
  3. species: species of plant whose photosynthetic rate was measured
    • m: Maianthemum canadense
    • u: Uvularia sessilifolia
  4. light: light level at which photosynthetic rate was measured
    • 0: shade (less than 300 uE/m2/s)
    • 1: sun (greater than 600 uE/m2/s)
  5. photo1: photosynthetic rate (umol CO2/m2/s), three measurements each over 30 seconds (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  6. photo2: photosynthetic rate (umol CO2/m2/s), three measurements each over 30 seconds (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  7. photo3: photosynthetic rate (umol CO2/m2/s), three measurements each over 30 seconds (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  8. meanphot: mean of the three photosynthetic measurements per leaf (unit: micromolePerMeterSquaredPerSecond / missing value: NA)
  9. trans1: calculated transpiration rates from Li-Cor measurements (unit: molePerMeterSquaredPerSecond / missing value: NA)
  10. trans2: calculated transpiration rates from Li-Cor measurements (unit: molePerMeterSquaredPerSecond / missing value: NA)
  11. trans3: calculated transpiration rates from Li-Cor measurements (unit: molePerMeterSquaredPerSecond / missing value: NA)
  12. meantran: mean of the three transpiration measurements per leaf (unit: molePerMeterSquaredPerSecond / missing value: NA)