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Harvard Forest Data Archive

HF045

Soil Warming Plus Nitrogen Addition Experiment at Harvard Forest since 2006

Related Publications

Data

Overview

  • Lead: Serita Frey
  • Investigators: Alexandra Contosta, Aaron Ellison, Melissa Knorr, Sydne Record, Linda van Diepen
  • Contact: Serita Frey
  • Start date: 2006
  • End date: 2017
  • Status: ongoing
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.54
  • Longitude: -72.18
  • Elevation: 365 meter
  • Taxa:
  • Release date: 2019
  • Revisions:
  • EML file: knb-lter-hfr.45.29
  • DOI: digital object identifier
  • Related links:
  • Study type: long-term measurement
  • Research topic: forest-atmosphere exchange; large experiments and permanent plot studies; soil carbon and nitrogen dynamics
  • LTER core area: organic matter, inorganic nutrients, disturbance
  • Keywords: ants, microbes, nitrogen, soil organic matter, soil respiration, soil warming, vegetation dynamics
  • Abstract:

    Climate warming and N deposition are occurring on a global scale with unknown long-term effects on soil microbial communities and the biogeochemical processes they perform. Few studies have examined the interactive effects of elevated temperatures and N additions on soil microbial community structure and function. The overall objective of this study is to investigate whether warming and N additions restructure microbial communities and alter the response of soil C pools to these two stressors. A related study is examining the interactive effects of warming and N additions on plant and ant diversity. This research is being carried out at the Soil Warming x Nitrogen Addition Study at the Harvard Forest which includes four treatments: control, warming (heating to 5 deg C above ambient), warming x N, and N additions only (addition of 50 kg N/ha/yr).

    Soil respiration measurements have been made monthly since the beginning of the experiment in 2006. In 2010 and 2011, two different methods were compared: static chamber measurements and instantaneous field IRGA assessments. Soil samples (~0-10 cm) have been sampled annually for total C and N, N mineralization, and microbial community composition. Most recently, soils were collected in October 2011 from across the entire profile (0-50 cm) to access potential changes in soil C and N pools with depth. First, 20 x 20 cm forest floor samples were collected. Mineral soils were then collected in 10 cm depth increments to ~50 cm. Samples are currently being analyzed for total C and N, microbial biomass and community composition and fungal gene expression (transcriptomics). Additionally, long-term incubations are being conducted to measure labile and recalcitrant C fractions. Additional soil physical (texture) and chemical (pH, inorganic N) are being measured.

    Field season measurements of soil respiration indicate that both warming and N additions continue to stimulate CO2 flux, with warming treatments having a stronger effect on respiration than N additions alone. Where warming x N occur together, warming appears to moderate the negative effects of N additions alone on soil respiration. Microbial biomass estimates show the greatest biomass within the warming x N treatment. Declines in microbial biomass with warming or N additions alone support similar findings from the same assessment in 2007 and 2009. Forest floor mass show small declines under warmed conditions. Soil C storage in the mineral soil showed modest changes with warming (-10% difference compared to control). Genomic and transcriptomic pipelines optimized in the Frey Lab are being used to measure the diversity, composition, and function (via gene expression) of the active fungal community in response to warming and N additions. Recent transcriptomic work has demonstrated that chronic N fertilization results in a decrease in expression of several transcripts of fungal laccase and glycoside hydrolases which are enzymes involved in lignocellulose degradation. Overall, our recent results suggest that anthropogenic stressors and seasonal changes continue to interact to affect soil microbial communities and biogeochemical cycles.

  • Methods:

    The experiment consists of four treatments (control, heated, heated +N, and +N only) with six replicates per treatment in a completely randomized design. The warming and N fertilization treatments were initiated in August 2006. Like the Soil Warming Study at Prospect Hill, average soil temperatures in the heated plots are continuously elevated 5 deg C above ambient by the use of buried heating cables placed at 10 cm depth in the soil and spaced 20 cm apart. The heating cables are controlled by a data logger that monitors thermistors every 10 min. Plots automatically turn on and off to maintain a 5 deg C temperature difference between the heated and control plots. The N addition plots (heated +N, +N only) are fertilized following the protocol of the Chronic Nitrogen Addition Study. An aqueous solution of NH4NO3 is applied at a rate equivalent to the low N plots at the chronic N study (5 g m-2 yr-1). Fertilizer is applied in equal monthly doses during the growing season (Apr-Oct). The unfertilized control plots and heated only plots are sprayed with water as a moisture control.

    Soil CO2 flux is measured by placing static chambers over pre-installed collars for 15 minutes, and taking headspace samples from these chambers at five minute intervals. Sampling occurs between 1100 and 1300 h. In the winter months, collars were dug from underneath the snow and allowed to equilibrate with the atmosphere for one hour prior to sampling. Gas samples are stored in air-tight, plastic syringes until they are transported back to the University of New Hampshire, and are analyzed using an infrared gas analyzer. The change in CO2 concentrations over the 15 minute sampling period was used to calculate net CO2 flux rates in units of mg CO2-C m-2 h-1.

    Plot temperatures are measured by thermistors buried to 5 cm depth in both heated and adjacent, unheated plots. Heated plots contain five thermistors each, while unheated plots contain two. The thermistors are connected to a Campbell Scientific CR10 datalogger, which reads them every 15 minutes and records the average plot temperature every hour.

    For the ant study, two pitfalls traps were placed within each plot. For 2006-2007, a pitfall trap consisted of one ten ounce cup placed flush with the ground. Approximately 20 ml of soapy water was put in each pitfall trap and trap contents were collected after 48 hours. For 2008-2009, a pitfall trap consisted of a 50 mL centrifuge placed in a PVC sleeve and filled with ~25 mL of ethanol with trap contents collected after 48 hours. Pitfalls were set to trap ants on days with clear, sunny weather and no rain. Ant sampling by S. Record occurred on: 28-30 June 2006, 11-13 July 2007, and 11-12 July 2009. M. Kaspari sampled ants in July 2008. Useful characteristics for distinguishing A. picea from A. rudis are still being worked out (and we used to call them all A. rudis), so this distinction will not be meaningful across years. To sample plants, S. Record counted all stems of every plant in each 3m x 3m plot and identified them to species when possible. Plant sampling dates were: 15-27 July 2006, 31 July 2007-16 Aug 2007, 2-13 Aug 2008, and 11-15 July 2009.

  • 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:

    Frey S. 2019. Soil Warming Plus Nitrogen Addition Experiment at Harvard Forest since 2006. Harvard Forest Data Archive: HF045.

Detailed Metadata

hf045-01: soil CO2 eflux

  1. date: date
  2. year: year
  3. month: month
  4. day: day of month
  5. plot: plot
  6. trt: treatment code
    • C: control
    • H: heated
    • HN: heated plus nitrogen
    • N: nitrogen
  7. rep: replicate number
  8. co2flux: CO2 flux (mg C m-2 h-1) (unit: milligramPerMeterSquaredPerHour / missing value: NA)
  9. moist: volumetric soil moisture (cm3 H2O cm3 soil-1) (unit: cubicCentimetersPerCubicCentimeters / missing value: NA)
  10. tsurf: soil surface temperature (°C) at time of sampling (unit: celsius / missing value: NA)
  11. t5cm: soil temperature (°C) at 5 cm depth at time of sampling (unit: celsius / missing value: NA)
  12. t10cm: soil temperature (°C) at 10 cm depth at time of sampling (unit: celsius / missing value: NA)

hf045-02: nitrogen mineralization

  1. date: date
  2. year: year
  3. month: month
  4. day: day of month
  5. plot: plot
  6. trt: treatment code
    • C: control
    • H: heated
    • HN: heated plus nitrogen
    • N: nitrogen
  7. rep: replicate number
  8. hor: soil horizon
    • mineral: mineral
    • organic: organic
  9. netno3: net mineralization of nitrate (NO3-) in mg kg-1 during the incubation period (unit: milligramPerKilogram / missing value: NA)
  10. netnh4: net mineralization of ammonium (NH4+) in mg kg-1 during the incubation period (unit: milligramPerKilogram / missing value: NA)
  11. daysincu: number of days of buried bag incubation (unit: number / missing value: NA)

hf045-03: soil temperature

  1. datetime: date and time
  2. year: year
  3. month: month
  4. day: day of month
  5. time: time of measurement (unit: number / missing value: NA)
  6. c1: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  7. c12: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  8. c14: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  9. c19: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  10. c20: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  11. c24: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  12. n6: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  13. n9: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  14. n21: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  15. h2: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  16. h5: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  17. h8: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  18. h13: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  19. h18: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  20. h22: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  21. hn3: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  22. hn4: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  23. hn7: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  24. hn10: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  25. hn15: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  26. hn17: temperature (°C) measured at 5cm depth (unit: celsius / missing value: NA)
  27. cmean: average temperature (°C) of control plots (unit: celsius / missing value: NA)
  28. nmean: average temperature (°C) of nitrogen plots (unit: celsius / missing value: NA)
  29. hmean: average temperature (°C) of heated plots (unit: celsius / missing value: NA)
  30. hnmean: average temperature (° C) of heated plus nitrogen plots (unit: celsius / missing value: NA)
  31. notes: notes

hf045-04: plants

  1. year: year
  2. plot: plot number
  3. treatment: treatment code
    • 1: control
    • 2: warm
    • 3: nitrogen
    • 4: warm/nitrogen
  4. acersp: number of stems of Acer species (unit: number / missing value: NA)
  5. acepen: number of stems of Acer pennsylvanicum (unit: number / missing value: NA)
  6. acerub: number of stems of Acer rubrum (unit: number / missing value: NA)
  7. aranud: number of stems of Aralia nudicaulis (unit: number / missing value: NA)
  8. aritri: number of stems of Arisaema triphyllum (unit: number / missing value: NA)
  9. betale: number of stems of Betula alleghaniensis (unit: number / missing value: NA)
  10. betlen: number of stems of Betula lenta (unit: number / missing value: NA)
  11. betspp: number of stems of Betula species (seedling) (unit: number / missing value: NA)
  12. carpen: number of stems of Carex pensylvanica (unit: number / missing value: NA)
  13. casden: number of stems of Castanea dentata (unit: number / missing value: NA)
  14. clibor: number of stems of Clintonia borealis (unit: number / missing value: NA)
  15. coptri: number of stems of Coptis trifolia (unit: number / missing value: NA)
  16. craspp: number of stems of Craetagus species (seedling) (unit: number / missing value: NA)
  17. denobs: number of stems of Dendrolycopodium obscurum (unit: number / missing value: NA)
  18. denpun: number of stems of Dennstaedtia punctilobula (unit: number / missing value: NA)
  19. dipcom: number of stems of Diphasiastrum complanatum (unit: number / missing value: NA)
  20. dryspp: number of stems of Dryopteris species (unit: number / missing value: NA)
  21. faggra: number of stems of Fagus grandifolia (unit: number / missing value: NA)
  22. gaupro: number of stems of Gaultheria procumbens (unit: number / missing value: NA)
  23. goopub: number of stems of Goodyera pubescens (unit: number / missing value: NA)
  24. hupluc: number of stems of Huperzia lucidula (unit: number / missing value: NA)
  25. lyolig: number of stems of Lyonia ligustrina (unit: number / missing value: NA)
  26. maican: number of stems of Maianthemum canadense (unit: number / missing value: NA)
  27. medvir: number of stems of Medeola virginiana (unit: number / missing value: NA)
  28. mitrep: number of stems of Mitchella repens (unit: number / missing value: NA)
  29. monuni: number of stems of Monotropa uniflora (unit: number / missing value: NA)
  30. pinstr: number of stems of Pinus strobus (unit: number / missing value: NA)
  31. pruser: number of stems of Prunus serotina (unit: number / missing value: NA)
  32. quealb: number of stems of Quercus alba (unit: number / missing value: NA)
  33. querub: number of stems of Quercus rubra (unit: number / missing value: NA)
  34. smirac: number of stems of Smilacina racemosa (unit: number / missing value: NA)
  35. snag: number of snags (unit: number / missing value: NA)
  36. tribor: number of stems of Trientalis borealis (unit: number / missing value: NA)
  37. tsucan: number of stems of Tsuga canadensis (unit: number / missing value: NA)
  38. unkspp: number of stems of unknown species (seedling with cotyledons only) (unit: number / missing value: NA)
  39. uvuses: number of stems of Uvularia sessilifolia (unit: number / missing value: NA)
  40. vaccspp: number of stems of Vaccinium species (corymbosum, angustifolium, vacillans) (unit: number / missing value: NA)
  41. vibace: number of stems of Viburnum acerifolium (unit: number / missing value: NA)
  42. vibden: number of stems of Viburnum dentatum (unit: number / missing value: NA)
  43. viblen: number of stems of Viburnum lentago (unit: number / missing value: NA)

hf045-05: ants

  1. year: year
  2. plot: plot number
  3. treatment: treatment code
    • 1: control
    • 2: warm
    • 3: nitrogen
    • 4: warm/nitrogen
  4. aphful: number of Aphaenogaster fulva (unit: number / missing value: NA)
  5. aphpic: number of Aphaenogaster picea. Note: useful characteristics for distinguishing A. picea from A. rudis are still being worked out (and we used to call them all A. rudis), so this distinction will not be meaningful across years. (unit: number / missing value: NA)
  6. aphrud: number of Aphaenogaster rudis. Note: useful characteristics for distinguishing A. picea from A. rudis are still being worked out (and we used to call them all A. rudis), so this distinction will not be meaningful across years. (unit: number / missing value: NA)
  7. camnov: number of Camponotus noveboracensis (unit: number / missing value: NA)
  8. campen: number of Camponotus pennsylvanicus (unit: number / missing value: NA)
  9. forase: number of Formica aserva (unit: number / missing value: NA)
  10. forneo: number of Formica neogagates (unit: number / missing value: NA)
  11. forrub: number of Formica rubicunda (unit: number / missing value: NA)
  12. forsubi: number of Formica subintegra (unit: number / missing value: NA)
  13. forsub: number of Formica subsericea (unit: number / missing value: NA)
  14. lasali: number of Lasius alienus (unit: number / missing value: NA)
  15. lasumb: number of Lasius umbratus (unit: number / missing value: NA)
  16. mryame: number of Myrmica americana (unit: number / missing value: NA)
  17. myrpun: number of Myrmica punctiventris (unit: number / missing value: NA)
  18. steimp: number of Stenamma impar (unit: number / missing value: NA)
  19. queen.notes: indicates presence of a queen