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Harvard Forest Data Archive

HF049

Gap Partitioning Among Maples at Harvard Forest 1986-1989

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Data

Overview

  • Lead: Timothy Sipe, Fakhri Bazzaz
  • Investigators:
  • Contact: Timothy Sipe
  • Start date: 1986
  • End date: 1989
  • Status: completed
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.54
  • Longitude: -72.17
  • Elevation: 350 meter
  • Taxa: Acer pensylvanicum (striped maple), Acer rubrum (red maple), Acer saccharum (sugar maple)
  • Release date: 2003
  • Revisions:
  • EML file: knb-lter-hfr.49.18
  • DOI: digital object identifier
  • Related links:
  • Study type: short-term measurement
  • Research topic: physiological ecology, population dynamics and species interactions
  • LTER core area: disturbance
  • Keywords: canopy gaps, microclimate, photosynthesis, regeneration, seedlings
  • Abstract:

    We measured shoot architecture, photosynthesis, survival and growth by seedlings of three shade-tolerant species of maple (Acer pensylvanicum, A. rubrum, A. saccharum) in an experimental test of the gap partitioning hypothesis. Trees were felled to create a total of six cleared, elliptical canopy gaps of two sizes (8m x 12m, 75m2; 16m x 24m, 300m2). Naturally-established, undamaged, unbranched seedlings (15-30 cm tall, 10-20+ years old) of the three study species (2160 total, 720 per species) were transplanted into five plot locations (center and NW, NE, SW, and SE gap edges) within all six gaps and matching understory sites one year before gap creation. All plots were weeded regularly and spaded annually along the edges to remove above and below-ground competition. Measurements of microclimates and non-competitive seedling responses were made over one year before and two years following gap release.

    Architectural variation increased greatly over the two-year period. Striped maple (A. pensylvanicum) and red maple (A. rubrum) increased branch numbers, leaf numbers, and total leaf areas in gaps, especially large gaps, while sugar maple (A. saccharum) showed much smaller changes. Red maple tended to increase the number of leaves while leaf size decreased; striped maple increased leaf number but held leaf size constant.

    Diurnal patterns of photosynthesis differed within and between gap and understory sites. Red maple showed higher photosynthetic rates per unit leaf area than striped and sugar maple in all site/plot combinations except the large gap south plots, where striped maple exceeded red maple. Estimated diurnal shoot-level assimilation differentiated species more than unit area assimilation rates, and also altered the rank order of performance, with striped maple above red maple above sugar maple in all microsites except the large gap north. Population-level assimilation versus irradiance response curves exhibited a similar pattern, with red maple dominating unit area rates in most plot microsites. In contrast, shoot assimilation curves showed striped maple above red maple above sugar maple in all microsites except the large gap north, where red maple exceeded striped maple. Architectural variation among these species interacted with leaf-level assimilation rates to produce some differences among these species in shoot-level assimilation across the gap-understory microclimatic gradient. Because survival and growth patterns are usually correlated with differences in whole-plant carbon assimilation, the results suggested that the potential for gap partitioning among the three maple species.

    Red maple survived better overall across the study due to greater persistence in the north and center plots of large gaps. The small gaps and understories showed no differences among the species. Survival rates exceeded 80% in most sites and plots, with low values (30-56%) only in the exposed plots of large gaps. There were no relationships between post-gap survival and previous age, height, or basal diameter. By the end of two years of gap release, both gap sizes induced greater distinctions among the species in all growth variables than the understory. Striped maple exhibited greater leader extension, absolute stem height, net height change, absolute basal diameter, and net basal diameter change than red maple and sugar maple (in that order) in nearly all sites and plots. The exception was large gap center and north plots, where red maple equaled or exceeded striped maple in net basal diameter change but not net height increase. Sugar maple was the least responsive of the species to the gap-understory gradient. As with survival, there were no predictable relationships between pre-gap age or size and post-gap growth.

    A considerable amount of leader (mainstem terminus) damage occurred during the study due to unknown causes. Architectural and growth analyses were done separately on undamaged seedlings versus those that had experienced leader damage and recovery. For all species combined, survival decreased while the frequency of leader damage among survivors increased across the gradient of microsite exposure. Red maple showed the highest survival (65-93%) but also very high leader damage (80-97%). Striped maple showed fairly high survival (81-93%) in all but the most exposed microsites (24-36%) and had the lowest leader damage overall (17-44%). Sugar maple was intermediate for both survival (25-86%) and leader damage (55-96%). Growth differed significantly among sites and species. Both intact and damaged plants showed greater growth in gaps than in understory, particularly in large gaps. For most growth variables in most microsites, striped maple equalled or exceeded red maple which equaled or exceeded sugar maple when plants were intact, but red maple equaled or exceeded striped maple which exceeded sugar maple when damaged. Species differences in growth varied among sites, with large gaps produced more pronounced effects than small gaps and understory for both intact and damaged plants. Growth recovery was inversely related to leader damage frequency among species, and thus at least partially offset the effects of damage on net growth across the populations.

    Photosynthetic performance paralleled growth by these species across the gradient, particularly for shoot assimilation. When growth variables were plotted against irradiance and temperature measured at seedling plot positions, there were consistent and clear distinctions among species across the gap-understory gradient, providing limited evidence for gap partitioning in our system for undamaged plants. Striped maple appears to be a superior generalist, red maple is a weaker generalist, and sugar maple shows the poorest performance in a manner that is nearly insensitive to the gap-understory gradient. Leader damage in the understory prior to gap formation would reinforce this pattern of relative performance by favoring striped maple. However, damaged red maple seedlings show a decisive advantage in recovery and regrowth in the large gap centers, where the probability of a juvenile trees capturing canopy gap space is highest.

  • Methods:

    Three large (300 m2) and three small (75 m2) canopy gaps were created in October 1987 by felling overstory trees across a 4-ha study area in the Prospect Hill 7 tract of the Harvard Forest. All gaps were elliptical with the long axis oriented east-west. Three large and three small understory sites were intermingled among the gaps. The twelve sites were divided into three blocks, with each block containing a large gap , small gap, large understory, and small understory site. Five seedling plots (1 x 2 m) were established in the gap centers and on the NW, NE, SW, and SE gap edges in advance of the tree felling. Five plots with the same geometric layout were also established in each of the understory sites.

    Gap and understory microclimates were measured for 3-5 days every other week during 1988 and 1989. Micromet stations were placed on the north edge of each of the 5 seedling plots in one large gap, one small gap, and one large understory site. Photosynthetic photon flux, air temperature (25 cm), and soil temperature at two depths (1 cm, 15 cm) were sampled simultaneously in all three sites every 10 seconds, and means were recorded every 10 minutes across 24-hour periods. Diurnal traces were plotted and also condensed to 12-hr daily totals, means, and standard errors. Most data analysis was focused on 5 clear, 5 overcast, and 10 combined (clear + overcast) days spread across the May-September growing season in 1989.

    The 2160 seedlings were transplanted from other sites in the Harvard Forest into the twelve understory and future gap sites in late fall 1986. The canopy gaps were created one year later after a growing season of acclimation to the understory, End-of-season seedling survival and growth (height, mainstem extension, branch growth, and basal diameter growth) were recorded one year before and two years following gap release.

    Shoot architecture was measured on a subset of 540 undamaged seedlings. These seedlings were selected in fall 1987 as representative of the complete set of 2160 seedlings based on morphological and age data. The 540 plants include 3 seedlings per species per plot per site per block across the experiment. Stem height, number of leaves, and leaf lengths were measured on several occasions annually in 1987-89.

    A subset of seedlings was selected for photosynthesis measurements on the north and south sides of one large gap, one small gap, and one large understory site in block 1 of the experiment. Sampling was scheduled such that all species were represented equally across sites and plots on each day of measurements. Diurnal patterns of leaf-level photosynthetic rates were measured in all sites on several days. Leaf-level rates were scaled to estimated shoot photosynthesis by combining shoot architectural data with photosynthetic rates measured on multiple leaf pairs on a random subset of seedlings for each species. Population-level light response curves were constructed for each species in each site from scatterplots of all measurements made across the growing season . The population curves were plotted for both leaf-level rates and estimated shoot photosynthesis.

  • 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:

    Sipe T, Bazzaz F. 2003. Gap Partitioning Among Maples at Harvard Forest 1986-1989. Harvard Forest Data Archive: HF049.

Detailed Metadata

hf049-01: micrometeorology

  1. stat: statistic
    • MEANS: mean
    • STDERRS: standard error
  2. daytype: day condition
    • CLEAR: clear day
    • OVER: overcast day
    • COMB: combination of clear and overcast day
  3. site: site
    • ALL: all
    • LGAP: large gap
    • SGAP: small gap
    • UND: understory
  4. plot: plot postitions in each site
  5. ppftot: total daily photosynthetic photon flux (mol/m2/12-hr day) (unit: molePerMeterSquaredPerDay / missing value: NA)
  6. ppfmean: mean daily photosynthetic photon flux (unit: molePerMeterSquaredPerSecond / missing value: NA)
  7. ppfqyr: duration of photosynthetic photon flux in quantum yield region (minutes per day when PPF = 0-25) (unit: molePerMeterSquaredPerSecond / missing value: NA)
  8. ppfopt: duration of photosynthetic photon flux in optimal region (minutes per day when PPF = 200-600) (unit: molePerMeterSquaredPerSecond / missing value: NA)
  9. ppfinh: duration of photosynthetic photon flux in inhibitory region (minutes per day when PPF is greater than 800) (unit: molePerMeterSquaredPerSecond / missing value: NA)
  10. tamean: mean daily air temperature (unit: celsius / missing value: NA)
  11. tainh: minutes per day when air temp greater than 25 C (unit: celsius / missing value: NA)
  12. ts1mean: mean daily surface soil temperature (unit: celsius / missing value: NA)
  13. ts15mean: mean daily deep soil temperature (unit: celsius / missing value: NA)

hf049-02: tree seedling architecture

  1. plcode: seedling code. Five digit code. First digit is experimental block # (1-3), second digit is site type (1-4, = large gap, large understory, small gap, small understory), third digit is plot position (1-5 = NW,NE,C, SW,SE), and final two digits are the position of the seedling in the plot (1-36, arranged as 4 rows of 9 seedlings, randomized by species across a 1 x 2 m plot).
  2. stat87: status in fall 1987
    • A: alive
    • D: dead
    • G: gone
  3. stat89: status in 1989
    • A: alive
    • D: dead
    • G: gone
  4. lstat87: leader status in 1987
    • N: leader gone
    • NA: leader present
  5. br87: branches present in fall 1987
    • Y: branches present
    • NA: branches absent
  6. ht87: height in fall 1987 (unit: millimeter / missing value: NA)
  7. lvpr87: number of leaf pairs in 1987 (unit: number / missing value: NA)
  8. lvno87: number of leaves in 1987 (unit: number / missing value: NA)
  9. lstat89: leader status in fall 1989
    • N: leader gone
    • Y: leader present
  10. brno89: number of branches in fall 1989 (unit: number / missing value: NA)
  11. ht89: height in fall 1989 (unit: millimeter / missing value: NA)
  12. lvpr89: number of leaf pairs in 1989 (unit: number / missing value: NA)
  13. lvno89: number of leaves in 1989 (unit: number / missing value: NA)
  14. lflgm89: mean leaf length in 1989 (unit: millimeter / missing value: NA)
  15. lfarm89: mean leaf area in 1989 (unit: squareCentimeters / missing value: NA)
  16. lfar89: total leaf area in 1989 (unit: squareCentimeters / missing value: NA)

hf049-03: tree seedling growth

  1. plcode: seedling code. Five digit code. First digit is experimental block # (1-3), second digit is site type (1-4, = large gap, large understory, small gap, small understory), third digit is plot position (1-5 = NW,NE,C, SW,SE), and final two digits are the position of the seedling in the plot (1-36, arranged as 4 rows of 9 seedlings, randomized by species across a 1 x 2 m plot).
  2. blk: expt. block (1-3)
  3. site: site
    • LG: large gap
    • LU: large understory
    • SG: small gap
    • SU: small understory
  4. plot: plot position. NW, NE, C, SW, and SE plot positions in each site.
  5. spp: species
    • R: Acer rubrum
    • S: Acer saccharum
    • P: Acer pensylvanicum
  6. stat88: status in fall 1988
    • A: alive
    • D: dead
    • G: gone
  7. stat89: status in fall 1989
    • A: alive
    • D: dead
    • G: gone
  8. ht87: height in fall 1987 (unit: millimeter / missing value: NA)
  9. ht89: height in fall 1989 (unit: millimeter / missing value: NA)
  10. lex88: leader extension 1988. Net growth of seedling mainstem during 1988. (unit: millimeter / missing value: NA)
  11. lex89: leader extension 1989. Net growth of seedling mainstem during 1989. (unit: millimeter / missing value: NA)
  12. bex89: branch extension 1989. Branch growth during 1989. (unit: millimeter / missing value: NA)
  13. tex89: total mainstem and branch net growth during 1987-89 (unit: millimeter / missing value: NA)
  14. bd87: basal diameter in 1987 (0.01 mm) (unit: millimeter / missing value: NA)
  15. bd88: basal diameter in 1988 (0.01 mm) (unit: millimeter / missing value: NA)
  16. bd89: basal diameter in 1989 (0.01 mm) (unit: millimeter / missing value: NA)
  17. bdc88: net change in basal diameter during 1988 (0.01 mm) (unit: millimeter / missing value: NA)
  18. bdc89: net change in basal diameter during 1989 (0.01 mm) (unit: millimeter / missing value: NA)
  19. htnet: net change in seedling height during 1987-89 (unit: millimeter / missing value: NA)
  20. lextot: leader growth. Net mainstem growth during 1987-89 (unit: millimeter / missing value: NA)
  21. bextot: total branch growth during 1987-89 (unit: millimeter / missing value: NA)
  22. textot: total mainstem and branch net growth during 1987-89 (unit: millimeter / missing value: NA)
  23. bdnet: net basal diameter change during 1987-89 (0.01 mm) (unit: millimeter / missing value: NA)
  24. age88: seedling age in 1988, measured using terminal bud scars (unit: number / missing value: NA)

hf049-04: photosynthetic gas exchange

  1. rec: unique record number
  2. date: date
  3. page: data page identifier, output from LI-6200 IRGA
  4. site: site
    • LG11: large gap
    • LG21: large gap
    • LU11: large understory
    • SG11: small gap
  5. plot: plot position. NW, NE, SW, SE and center plots of each site.
  6. plant: plant code. Letter = species (P = Acer pensylvanicum, R = A. rubrum, S = A. saccharum), two-digit number is seedling location within the 1 x 2 m seedling plot (36 locations, 25 cm apart, in an array of 4 rows of 9 seedlings each)
  7. hr: time of measurement (hour) (unit: nominalHour / missing value: NA)
  8. min: time of measurement (minute) (unit: nominalMinute / missing value: NA)
  9. sec: time of measurement (second) (unit: second / missing value: NA)
  10. qntm: irradiance level (photosynthetic photon flux ( next to the leaf) (unit: molePerMeterSquaredPerSecond / missing value: NA)
  11. tair: air temperature inside the LI-6200 cuvette (unit: celsius / missing value: NA)
  12. tleaf: leaf temperature (unit: celsius / missing value: NA)
  13. tco2: temperature of the infrared gas analyzer (unit: celsius / missing value: NA)
  14. co2: mean CO2 concentration inside cuvette during measurements (ppm) (unit: number / missing value: NA)
  15. flow: air flow rate through the cuvette (unit: number / missing value: NA)
  16. rhum: relative humidity (unit: dimensionless / missing value: NA)
  17. eair: vapor pressure (unit: millibar / missing value: NA)
  18. cint: CO2 concentration in leaf intercellular air space (calculated, ppm) (unit: number / missing value: NA)
  19. photo: net photosynthetic rate (mol C/m2/s) (unit: molePerMeterSquaredPerSecond / missing value: NA)
  20. trans: transpiration rate (unit: millimolePerMeterSquaredPerSecond / missing value: NA)
  21. cmol: stomatal conductance (flux) (unit: millimolePerMeterSquaredPerSecond / missing value: NA)
  22. cs: stomatal conductance (unit: centimetersPerSecond / missing value: NA)