Harvard Forest

Data Archive

HF018

Barre Woods Soil Warming Experiment at Harvard Forest since 2001

Related Publications

Data

• hf018-01: trace gas (pre-treatment) (preview)
• hf018-02: canopy foliage (pre-treatment) (preview)
• hf018-03: soil temperature (preview)
• hf018-04: soil moisture (preview)
• hf018-05: lysimeter (preview)
• hf018-06: nitrogen mineralization (preview)
• hf018-07: soil respiration (preview)
• hf018-08: dendrology (preview)
• hf018-09: litterfall (preview)
• hf018-10: foliage chemistry (preview)
• hf018-11: spring budbreak (preview)
• hf018-12: litter chemistry (preview)
• hf018-13: water holding capacity (preview)

Overview

• Lead: Serita Frey, Jerry Melillo
• Investigators: Melissa Knorr
• Contact: Information Manager
• Start date: 2001
• End date: 2022
• Status: ongoing
• Location: Slab City Tract (Harvard Forest)
• Latitude: +42.48 degrees
• Longitude: -72.18 degrees
• Elevation:
• Datum: WGS84
• Taxa: Acer rubrum (red maple), Acer saccharum (sugar maple), Betula alleghaniensis (yellow birch), Betula lenta (black birch), Fraxinus americana (white ash), Pinus strobus (white pine), Quercus rubra (red oak), Quercus velutina (black oak), Tsuga canadensis (hemlock)
• Release date: 2025
• Language: English
• EML file: knb-lter-hfr.18.37
• DOI: digital object identifier
• EDI: data package
• DataONE: data package
• Related links:
• Prospect Hill Soil Warming Experiment at Harvard Forest since 1991
• Study type: long-term measurement
• Research topic: large experiments and permanent plot studies; soil carbon and nitrogen dynamics
• LTER core area: mineral cycling, disturbance patterns
• Keywords: carbon, carbon dioxide, climate change, methane, nitrogen, nitrogen mineralization, nitrous oxide, soil moisture, soil respiration, soil temperature, soil warming
• Abstract:

  Two of the major results of our original soil warming study were that: (1) warming stimulated the decay of a labile soil carbon pool; and (2) it also increased the availability of inorganic nitrogen to plants. Because of the small size of the original warming plots an important question we have not been able to answer conclusively is: Has the increase in available nitrogen led to an increase in carbon storage in the vegetation? And if yes, how much? In a systems context an additional question is: What is the balance between the carbon lost from the soil and the carbon stored in the vegetation in response to soil warming?

  We are now addressing these important questions with a new warming experiment in the Barre Woods area of the Harvard Forest. The Barre Woods site was chosen because of its similarities to the Prospect Hill site - stand age, tree species composition, and soil type. There is no evidence of a plow horizon at the Barre Woods site, though surrounding stone walls indicate past use as pastureland. Historical records indicate the site was destroyed during the 1938 hurricane and then regrew naturally.

  During the summer and fall of 2001 we buried 3.4 miles of heating cable in a 30 x 30m plot. Cables were buried at a 10cm depth, spaced 20cm apart. A second 30 x 30m area was delineated to serve as the control plot. Results from the original soil warming experiment confirmed that the soil disturbance associated with the installation of heating cables has had no effect on soil temperatures and only minor and variable impacts on soil moisture.

  In April 2002, we began a one-year period of baseline measurements before turning on the heat in the new megaplot. These measurements included nitrogen mineralization, trace gas fluxes (CO2, CH4, N2O), tree growth (dendrometer bands), an understory species survey, canopy foliage analysis (C:N, NIR), and lysimetry. Thermistors were installed in both plots to begin tracking soil temperatures. The baseline measurements have confirmed that there are no significant differences between the two plots for key ecosystem processes prior to the initiation of the warming manipulation.

  We will turn on the power in April 2003 to begin the "manipulation phase" of this study. From this study, we expect to determine whether or not warming results in the movement of nitrogen from the soil to the trees and to learn how this movement affects the net carbon balance of the ecosystem.

• Methods:

  The soil in the heated plot was warmed using the buried heating cable method. Heated and control plot temperatures were evaluated on 10 minute intervals by a datalogger, and the heating cables turned on or off accordingly to maintain a difference between the heated and control plot of 5 degrees C. Heated and control plot temperature moisture were recorded on four hour intervals from 2003-2008, and on hourly intervals from 2009 on.

  Soil respiration was measured by placing chamber lids over permanent collars installed in the plots for 15 minutes and sampling the headspace gas at 5 minute intervals. CO2 was measured for the duration of the experiment to date, and CH4 and N2O were measured from 2003-2007. CO2 sample concentrations were measured with an infrared gas analyzer, and CH4 and NO2 sample concentrations were measured by gas chromatography. Fluxes were calculated based on the changes in concentrations over the incubation period. Soil temperatures were measured at 2 and 4cm at the time of each gas sampling. Soil moisture measurements were conducted using gravimetric techniques for the first year of the study and by automated time domain reflectometry (TDR) starting in 2003.

  Net N mineralization and nitrification were measured for the forest floor and mineral soil using an on-site buried bag incubation. Incubations were for 5 weeks, April- November, and for 5 months through the winter. Initial samples were collected and analyzed for extractable (2N KCl, 48 hours) NH4+ and NO3- content. The same analysis was carried out on the incubated samples. The difference in total mineral N content between initial and incubated soils is the net mineralization rate.

  Concentrations of inorganic N in water leaching below the rooting zone were measured using high-tension lysimetry. Soil water samples were collected from 6 porous cup lysimeters per plot, monthly, although in some months no sample was recovered from some or all lysimeters. Lysimeters were installed at a depth of 50 cm and evacuated to ~15 in Hg 24 h before sampling. Samples were frozen until they were analyzed for NH4+ and NO3-.

  Tree growth was quantified using dendrometer bands on all trees greater than 9cm DBH. Measurements were made monthly during the growing season.

  Canopy chemistry was evaluated (preferentially sun leaves) at the height of the growing season. Leaves were sampled by shotgun in July or August. Analyses were done for C, N (by CHN analysis), cellulose and lignin (using NIR), 13C and 15N (stable isotope mass spectroscopy).

  Spring budbreak was measured by visually estimating for each tree the percentage of its leaves that had emerged from their buds.

  Litterfall was collected each fall from permanent baskets installed in the plots. Wire baskets dispersed throughout the plots were used from 2003-2009; laundry baskets clustered in the center of the plots were used from 2006-present.

  Water holding capacity was measured as field capacity; the mass of water the soil can retain against gravity drainage. Soil samples were saturated in water for 24 hours in mesh-bottomed tubes, and then placed on a metal grate and allowed to drain for another 24 hours. After draining, the water content of the soil was measured gravimetrically (soil samples were weighed, dried in an oven at 105 C for 48 hours, then reweighed).

  SOM content was measured by combustion in a muffle furnace at 550 C for 4 hours. Dry soil samples were weighed, combusted, and then reweighed.

• Organization: Harvard Forest. 324 North Main Street, Petersham, MA 01366, USA. Phone (978) 724-3302. Fax (978) 724-3595.

• Project: The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts. (ROR).

• Funding: National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210.

• 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.

• License: Creative Commons Zero v1.0 Universal (CC0-1.0)

• Citation: Frey S, Melillo J. 2025. Barre Woods Soil Warming Experiment at Harvard Forest since 2001. Harvard Forest Data Archive: HF018 (v.37). Environmental Data Initiative: https://doi.org/10.6073/pasta/8becbc2b5a15f37cddc94b332b65e78a.

Detailed Metadata

hf018-01: trace gas (pre-treatment)

1. date: collection date
2. year: year
3. month: month
4. day: day
5. treatment: treatment
6. plot: plot number
7. ch4: ch4 flux (unit: milligramPerMeterSquaredPerHour / missing value: NA)
8. n2o: n2o flux (unit: milligramPerMeterSquaredPerHour / missing value: NA)
9. temp2: soil temperature at 2 cm depth (unit: celsius / missing value: NA)
10. temp5: soil temperature at 5 cm depth (unit: celsius / missing value: NA)

hf018-02: canopy foliage (pre-treatment)

1. tree: tree ID
2. date: collection date
3. species: species name
4. plot: treatment code
   • c: control
   • h: heated
5. n_per: % nitrogen (unit: number / missing value: NA)
6. lignin_per: % lignin (unit: number / missing value: NA)
7. cellulose_per: % cellulose (unit: number / missing value: NA)

hf018-03: soil temperature

1. datetime: date and time
2. doy: Julian day (unit: nominalDay / missing value: NA)
3. year: year
4. time: time
5. ctrl_av: average soil temperature Control plot (unit: celsius / missing value: NA)
6. p1_av: average soil temperature Block 1 Heated Plot (unit: celsius / missing value: NA)
7. p2_av: average soil temperature Block 2 Heated Plot (unit: celsius / missing value: NA)
8. p3_av: average soil temperature Block 3 Heated Plot (unit: celsius / missing value: NA)
9. p4_av: average soil temperature Block 4 Heated Plot (unit: celsius / missing value: NA)
10. p5_av: average soil temperature Block 5 Heated Plot (unit: celsius / missing value: NA)
11. p6_av: average soil temperature Block 6 Heated Plot (unit: celsius / missing value: NA)
12. p7_av: average soil temperature Block 7 Heated Plot (unit: celsius / missing value: NA)
13. p8_av: average soil temperature Block 8 Heated Plot (unit: celsius / missing value: NA)
14. p9_av: average soil temperature Block 8 Heated Plot (unit: celsius / missing value: NA)
15. p10_av: average soil temperature Block 10 Heated Plot (unit: celsius / missing value: NA)

hf018-04: soil moisture

1. datetime: date and time
2. year: year
3. doy: Julian day (unit: nominalDay / missing value: NA)
4. time: time
5. tdr1: soil moisture TDR probe 1 in the Heated Plot (%VWC) (unit: dimensionless / missing value: NA)
6. tdr2: soil moisture TDR probe 2 in the Heated Plot (%VWC) (unit: dimensionless / missing value: NA)
7. tdr3: soil moisture TDR probe 3 in the Heated Plot (%VWC) (unit: dimensionless / missing value: NA)
8. tdr4: soil moisture TDR probe 4 in the Heated Plot (%VWC) (unit: dimensionless / missing value: NA)
9. tdr5: soil moisture TDR probe 5 in the Heated Plot (%VWC) (unit: dimensionless / missing value: NA)
10. tdr6: soil moisture TDR probe 6 in the Heated Plot (%VWC) (unit: dimensionless / missing value: NA)
11. tdr7: soil moisture TDR probe 1 in the Control Plot (%VWC) (unit: dimensionless / missing value: NA)
12. tdr8: soil moisture TDR probe 2 in the Control Plot (%VWC) (unit: dimensionless / missing value: NA)
13. tdr9: soil moisture TDR probe 3 in the Control Plot (%VWC) (unit: dimensionless / missing value: NA)
14. tdr10: soil moisture TDR probe 4 in the Control Plot (%VWC) (unit: dimensionless / missing value: NA)
15. tdr11: soil moisture TDR probe 5 in the Control Plot (%VWC) (unit: dimensionless / missing value: NA)
16. tdr12: soil moisture TDR probe 6 in the Control Plot (%VWC) (unit: dimensionless / missing value: NA)
17. probeset: set of soil moisture probes
    • 0: original set of soil moisture probes installed in 2003
    • 1: set of replacement probes installed in control plot in 2016 (original probes retained in heated plot)

hf018-05: lysimeter

1. date: collection date
2. year: year
3. month: month
4. day: day
5. plot: plot ID
6. treatment: treatment
   • C: control plot
   • H: heated plot
7. nh4: ammonium (unit: milligramsPerLiter / missing value: NA)
8. no3: nitrate (unit: milligramsPerLiter / missing value: NA)

hf018-06: nitrogen mineralization

1. year: year
2. month: month
3. treatment: treatment
   • c: control plot
   • h: heated plot
4. plot: plot ID
5. sum_ion: NH4 + NO3 (kgN/ha/month) (unit: kilogramsPerHectarePerMonth / missing value: NA)
6. nh4: ammonification rate (kgN/ha/monh) (unit: kilogramsPerHectarePerMonth / missing value: NA)
7. no3: nitrification rate (kgN/ha/month) (unit: kilogramsPerHectarePerMonth / missing value: NA)

hf018-07: soil respiration

1. datetime: collection date and time
2. date: collection date
3. year: year
4. month: month
5. day: day
6. time: time
7. treatment: treatment code
   • C: control plot
   • H: heated plot
8. plot: subplot within the megaplot
9. co2: CO2 flux in mg C m-2 h-1 (unit: milligramPerMeterSquaredPerHour / missing value: NA)
10. cm2: soil temperature at 2 cm depth (unit: celsius / missing value: NA)
11. cm4: soil temperature at 4 cm depth (unit: celsius / missing value: NA)
12. moisture: soil moisture (% volumetric moisture content) (unit: dimensionless / missing value: NA)
13. measurement: measurement type
    • Li8100-a: automatic LI-COR measurement
    • static: static chamber gas syringe measurement

hf018-08: dendrology

1. treeid: unique identification number assigned to each tree in experiment
2. date: date
3. species: species code
   • ACPE: Acer pensylvanicum, striped maple
   • ACRU: Acer rubrum, red maple
   • ACSA: Acer saccharum, sugar maple
   • ACSP: Acer species, unidentified maple
   • BEAL: Betula alleghaniensis, yellow birch
   • BELE: Betula lenta, black birch
   • BEPA: Betula papyrifera, paper birch
   • BEPO: Betula populifolia, gray birch
   • BESP: Betula species, unidentified birch
   • CADE: Castanea dentata, american chestnut
   • FAGR: Fagus grandifolia, american beech
   • FRAM: Fraxinus americana, white ash
   • PIST: Pinus strobus, white pine
   • POGR: Populus grandidentata, bigtooth aspen
   • PRSE: Prunus serotina, black cherry
   • QUAL: Quercus alba, white oak
   • QURU: Quercus rubra, red oak
   • QUSP: Quercus species, unidentified oak
   • QUVE: Quercus velutina, black oak
   • TSCA: Tsuga canadensis, eastern hemlock
4. plot: plot
   • B: wide buffer zone around plots
   • Be: portion of buffer zone within 15 meters of an edge
   • Bh: portion of buffer zone within 10 meters of heated plot
   • Bhe: portion of buffer zone both within 10 meters of heated plot and 15 meters of an edge
   • C: control
   • H: heated
   • S1: supplemental control plot 1
   • S2: supplemental control plot 2
   • S3: supplemental control plot 3
   • S4: supplemental control plot 4
5. subplot: 5x5 meter subplot within the C or H plot
6. dbh: diameter at breast height (unit: centimeter / missing value: NA)

hf018-09: litterfall

1. year: year
2. treatment: plot
   • C: control
   • H: heated
3. species: species code
   • ACPE: Acer pensylvanicum, striped maple
   • ACRU: Acer rubrum, red maple
   • ACSA: Acer saccharum, sugar maple
   • BESP: Betula species, unidentified birch
   • CADE: Castanea dentata, american chestnut
   • FAGR: Fagus grandifolia, american beech
   • FRAM: Fraxinus americana, white ash
   • OTHER: other
   • POGR: Populus grandidentata, bigtooth aspen
   • PRSE: Prunus serotina, black cherry
   • QUAL: Quercus alba, white oak
   • QURU: Quercus rubra, red oak
   • UNKN: unknown (mostly unidentifiable fragments)
4. basket_num: unique identification number of litter collection basket
5. basket_type: type of litter basket
   • WB: wire basket (capture area 0.3215 m2)
   • LB: laundry basket (capture area 0.2145 m2)
6. mass: total dry weight of litterfall captured (unit: gram / missing value: NA)

hf018-10: foliage chemistry

1. year: year
2. treeid: unique identification number assigned to each tree in experiment
3. species: species code
   • ACRU: Acer rubrum, red maple
   • ACSA: Acer saccharum, sugar maple
   • BEAL: Betula alleghaniensis, yellow birch
   • BEPO: Betula populifolia, gray birch
   • BESP: Betula species, unidentified birch
   • FRAM: Fraxinus americana, white ash
   • QURU: Quercus rubra, red oak
   • QUVE: Quercus velutina, black oak
   • TSCA: Tsuga canadensis, eastern hemlock
4. treatment: plot
   • H: Heated
   • C: Control
5. n_per: weight percent nitrogen (unit: dimensionless / missing value: NA)
6. c_per: weight percent carbon (unit: dimensionless / missing value: NA)
7. c_n: molar carbon to nitrogen ratio (unit: dimensionless / missing value: NA)
8. d13c: d13C, o/oo vs. PDB (unit: dimensionless / missing value: NA)
9. d15n: d15N, o/oo vs. air (unit: dimensionless / missing value: NA)
10. p_per: weight percent phosphorus (unit: dimensionless / missing value: NA)
11. n_p: molar nitrogen to phosphorus ratio (unit: dimensionless / missing value: NA)

hf018-11: spring budbreak

1. date: collection date
2. tree: unique identification number assigned to each tree in experiment
3. plot: treatment
   • C: Control
   • H: Heated
4. species: species code
   • ACPE: Acer pensylvanicum, striped maple
   • ACRU: Acer rubrum, red maple
   • ACSA: Acer saccharum, sugar maple
   • BEAL: Betula alleghaniensis, yellow birch
   • BELE: Betula lenta, black birch
   • BEPA: Betula papyrifera, paper birch
   • BEPO: Betula populifolia, gray birch
   • CADE: Castanea dentata, american chestnut
   • FRAM: Fraxinus americana, white ash
   • QUAL: Quercus alba, white oak
   • QURU: Quercus rubra, red oak
   • QUVE: Quercus velutina, black oak
5. year: year
6. doy: day of year (Julian day) (unit: nominalDay / missing value: NA)
7. budbreak: visually estimated percentage of buds from which leaves have emerged and unfolded, to the nearest 10% (unit: dimensionless / missing value: NA)

hf018-12: litter chemistry

1. year: year
2. species: species code
   • ACRU: Acer rubrum, red maple
   • ACPE: Acer pensylvanicum, striped maple
   • ACSA: Acer saccharum, sugar maple
   • ACSP: Acer species, unidentified maple
   • BEAL: Betula alleghaniensis, yellow birch
   • BELE: Betula lenta, black birch
   • BESP: Betula species, unidentified birch
   • FRAM: Fraxinus americana, white ash
   • CADE: Castanea dentata, american chestnut
   • FAGR: Fagus grandifolia, american beech
   • POGR: Populus grandidentata, bigtooth aspen
   • UNKN: unknown (mostly unidentifiable fragments)
   • PIST: Pinus strobus, white pine
   • PRSE: Prunus serotina, black cherry
   • QUAL: Quercus alba, white oak
   • QURU: Quercus rubra, red oak
   • QUSP: Quercus species, unidentified oak
3. treatment: plot
   • C: control
   • H: heated
4. basket_num: unique identification number of litter collection basket
5. basket_type: type of litter basket
   • WB: wire basket (capture area 0.3215 m2)
   • LB: laundry basket (capture area 0.2145 m2)
6. c_per: weight percent carbon of litter (unit: dimensionless / missing value: NA)
7. n_per: weight percent nitrogen of litter (unit: dimensionless / missing value: NA)
8. c_n: molar C:N ratio of litter (unit: dimensionless / missing value: NA)
9. p_per: weight percent phosphorus (unit: dimensionless / missing value: NA)
10. n_p: molar nitrogen to phosphorus ratio (unit: dimensionless / missing value: NA)

hf018-13: water holding capacity

1. date: sampling date
2. plot: plot
   • Control: control plot
   • Heated: heated plot
3. subplot: 5 x 5 meter subplot within main plots; 1-36
4. horizon: horizon
   • Organic: organic
   • Mineral: mineral
5. som: soil organic matter content; g organic matter dry weight (unit: gram / missing value: NA)
6. whc: soil water holding capacity; g water at capacity (unit: gram / missing value: NA)