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Harvard Forest Data Archive

HF212

Radiocarbon Measurements at Harvard Forest 1996-2010

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Data

Overview

  • Lead: Susan Trumbore
  • Investigators: Eric Davidson, Serita Frey, Kathleen Savage, Carlos Sierra
  • Contact: Kathleen Savage
  • Start date: 1996
  • End date: 2010
  • Status: completed
  • Location: Prospect Hill Tract (Harvard Forest)
  • Latitude: +42.53 to +42.55
  • Longitude: -72.20 to -72.17
  • Elevation: 280 to 420 meter
  • Taxa:
  • Release date: 2013
  • Revisions:
  • EML file: knb-lter-hfr.212.5
  • DOI: digital object identifier
  • Related links:
  • Study type: long-term measurement
  • Research topic: soil carbon and nitrogen dynamics
  • LTER core area: inorganic nutrients
  • Keywords: carbon, climate change, modeling, nitrogen, soil respiration, soil temperature
  • Abstract:

    Long-term datasets on soil C stocks, radiocarbon content, and CO2 efflux from the Harvard forest, MA were applied to the ForCent model to examine soil C dynamics over long term timescales and under warming and nitrogen amendments. The objective was to determine if manipulations of soil temperature and nitrogen supply affect the relative age of respired soil C substrates. Heating of the soil increased decomposition of all soil C pools, the absolute amount of increased decomposition from the older pools was not large enough to make a difference in 14C composition of respired C from model results. Further the high spatial variation observed in 14C from temperature and nitrogen amendments made it difficult to detect changes in respired C sources over this short a study period.

  • Methods:

    Soil Respired 14C

    Samples for isotopic measurements in soil CO2 efflux were collected from soil respiration chambers (described above) that enclosed air headspace in contact with the soil surface using a closed dynamic chamber system to collect accumulated CO2 in stainless steel traps. Details about the method are presented in Gaudinski et al. (2000) and Sierra et al. (2012). All measurements of respired 14C are also presented in the Sierra et al. (2012) manuscript.

    Radiocarbon in Organic Matter Fractions

    Soil samples were collected in 1996 from the soil pits described above and analyzed for radiocarbon. In 2007, three new soils pits were dug at locations within 1-5 meters of the original soil pits sampled in 1996 by J. Gaudinski for analysis of radiocarbon organic matter fraction (Sierra et al., 2012). Soils were sieved (to less than 2 mm), and large roots removed. Treatment of soil samples and isolation of fractions was the same as reported in Gaudinski et al. (2000) and Sierra et al. (2012). Data are reported as the average of the three replicates, the error bar represents the standard deviation. Radiocarbon measurements are reported as ∆14C values (Stuiver and Polach 1977), the deviation of the 14C/12C ratio in the sample (SN) from the 14C/12C ratio value of oxalic acid decay-corrected (ABS). These same measurements of organic matter fractions used in this manuscript are also presented in Sierra et al. (2012).

  • 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:

    Trumbore S. 2013. Radiocarbon Measurements at Harvard Forest 1996-2010. Harvard Forest Data Archive: HF212.

Detailed Metadata

hf212-01: respired 14C - no treatment

  1. date: date
  2. year: year
  3. doy: day of year (unit: nominalDay )
  4. year.date: sample date by year (unit: nominalYear / missing value: NA)
  5. delta.14c: respired 14C (o/oo) (unit: dimensionless )
  6. site: site name. There are 6 sites located along a northwest and southwest transect from the EMS tower on the Prospect Hill tract of the Harvard forest. Sites ranged from very poorly drained swamp to well drained uplands.

hf212-02: respired 14C - with treatment

  1. treat.cham: treatment code and chamber number. Treatment codes: C: control, H: heated, HN: heated plus nitrogen, N: nitrogen.
  2. date: sample date
  3. delta.14c: respired 14C (o/oo) (unit: dimensionless / missing value: NA)

hf212-03: radio carbon in organic fractions

  1. year: sample year
  2. layer: soil layer
    • Organic: organic soil
    • Mineral: mineral soil
  3. horizon: soil horizon
    • Oi: organic horizon
    • Oe: organic e horizon
    • A-lf: mineral A light fraction
    • A-min: mineral A horizon
  4. of.14c.12c: radio carbon in organic fraction (unit: dimensionless )