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Soil Warming Plus Nitrogen Addition Experiment

HF045 EML Publications Archive

Data

Overview

  • Lead: Serita Frey
  • Investigators: Alexandra Contosta, Melissa Knorr
  • Contact: Serita Frey
  • Start date: 2006-06-14
  • End date: ongoing
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.54
  • Longitude: -72.18
  • Elevation: 365
  • Taxa:
  • Research topic: plot, soil
  • Study type: long-term measurement
  • LTER core area: inorganic nutrients, disturbance
  • Keywords: microbial community, nitrogen additions, soil organic matter, soil respiration, soil warming
  • Release date: 2009
  • EML version: knb-lter-hfr.45.8
  • Revisions:
  • Related links:
  • Abstract:

    The purpose of this experiment is to examine the interactive effects of warming and N additions on the soil microbial community and soil nutrient cycling. 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.

    In June and July of 2006, we collected pretreatment samples of soil respiration and net N mineralization. Soil CO2 flux and net N mineralization did not significantly differ prior to the initiation of the experimental treatments. Soil respiration in heated and heated plus N plots showed significantly higher fluxes following the initiation of the warming and fertilization manipulations. Likewise, net N mineralization was similar across all treatments during June and July 2006. By October 2006, heated and heated plus nitrogen plots showed higher rates of N mineralization as compared to control and N only plots.

  • Methods:

    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. 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.

    Net N mineralization and net nitrification are determined using the buried bag technique, where the values of extractable nitrate-N and ammonium-N are compared in initial and incubated soil cores. Incubations occur in situ for approximately one month, and take place two weeks following the most recent fertilizer application. Both initial and incubated cores are extracted using 2M KCl, filtered, and frozen at 0 deg C pending analysis of NH4+ and NO3-.

  • Use:

    This dataset is released to the public and may be freely downloaded. 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. For more information on LTER Network data access and use policies, please see: http://www.lternet.edu/data/netpolicy.html.

  • Citation:

    Frey S. 2009. Soil Warming Plus Nitrogen Addition Experiment. Harvard Forest Data Archive: HF045.

Detailed Metadata

hf045-01: soil CO2 eflux

  1. YEAR: year (YYYY)
  2. MONTH: month (MM)
  3. DAY: day of month (DD)
  4. PLOT: plot
  5. TRT: treatment code
    • C: control
    • H: heated
    • HN: heated plus nitrogen
    • N: nitrogen
  6. REP: replicate number
  7. CO2FLUX: CO2 flux (mg C m-2 h-1) (milligramsPerMeterSquaredPerHour )
  8. MOIST: volumetric soil moisture (cm3 H2O cm3 soil-1) (cubicCentimetersPerCubicCentimeters )
  9. TSURF: soil surface temperature (°C) at time of sampling (celsius )
  10. T5CM: soil temperature (°C) at 5 cm depth at time of sampling (celsius )
  11. T10CM: soil temperature (°C) at 10 cm depth at time of sampling (celsius )

hf045-02: nitrogen mineralization

  1. YEAR: year (YYYY)
  2. MONTH: month (MM)
  3. DAY: day of month (DD)
  4. PLOT: plot
  5. TRT: treatment code
    • C: control
    • H: heated
    • HN: heated plus nitrogen
    • N: nitrogen
  6. REP: replicate number
  7. HOR: soil horizon
    • mineral: mineral
    • organic: organic
  8. NETNO3: net mineralization of nitrate (NO3-) in mg kg-1 during the incubation period (milligramsPerKilogram )
  9. NETNH4: net mineralization of ammonium (NH4+) in mg kg-1 during the incubation period (milligramsPerKilogram )
  10. DAYSINCU: number of days of buried bag incubation (number )

hf045-03: soil temperature

  1. YEAR: year (YYYY)
  2. MONTH: month (MM)
  3. DAY: day of month (DD)
  4. C1: temperature (°C) measured at 5cm depth (celsius )
  5. C12: temperature (°C) measured at 5cm depth (celsius )
  6. C14: temperature (°C) measured at 5cm depth (celsius )
  7. C19: temperature (°C) measured at 5cm depth (celsius )
  8. C20: temperature (°C) measured at 5cm depth (celsius )
  9. C24: temperature (°C) measured at 5cm depth (celsius )
  10. N6: temperature (°C) measured at 5cm depth (celsius )
  11. N9: temperature (°C) measured at 5cm depth (celsius )
  12. N21: temperature (°C) measured at 5cm depth (celsius )
  13. H2: temperature (°C) measured at 5cm depth (celsius )
  14. H5: temperature (°C) measured at 5cm depth (celsius )
  15. H8: temperature (°C) measured at 5cm depth (celsius )
  16. H13: temperature (°C) measured at 5cm depth (celsius )
  17. H18: temperature (°C) measured at 5cm depth (celsius )
  18. H22: temperature (°C) measured at 5cm depth (celsius )
  19. HN3: temperature (°C) measured at 5cm depth (celsius )
  20. HN4: temperature (°C) measured at 5cm depth (celsius )
  21. HN7: temperature (°C) measured at 5cm depth (celsius )
  22. HN10: temperature (°C) measured at 5cm depth (celsius )
  23. HN15: temperature (°C) measured at 5cm depth (celsius )
  24. HN17: temperature (°C) measured at 5cm depth (celsius )
  25. CMEAN: average temperature (°C) of control plots (celsius )
  26. NMEAN: average temperature (°C) of nitrogen plots (celsius )
  27. HMEAN: average temperature (°C) of heated plots (celsius )
  28. HNMEAN: average temperature (° C) of heated plus nitrogen plots (celsius )
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