Harvard Forest

Data Archive

HF008

Chronic Nitrogen Amendment Experiment at Harvard Forest since 1988

Related Publications

Data

• hf008-01: foliar chemistry (preview)
• hf008-02: litter chemistry (preview)
• hf008-03: litterfall biomass (preview)
• hf008-04: tree inventory (preview)
• hf008-05: tension lysimeters (preview)
• hf008-06: soil CN and mineralization (preview)
• hf008-07: litter decomposition (preview)
• hf008-08: zero tension lysimeters (preview)
• hf008-09: litterfall since 2003 (preview)
• hf008-10: ants 2003 (preview)

Overview

• Lead: Serita Frey, Scott Ollinger
• Investigators: Michelle Day, Richard MacLean, Mary Martin
• Contact: Information Manager
• Start date: 1988
• End date: 2022
• Status: ongoing
• Location: Prospect Hill Tract (Harvard Forest)
• Latitude: +42.54 degrees
• Longitude: -72.18 degrees
• Elevation: 385 meter
• Datum: WGS84
• Taxa: Acer rubrum (red maple), Betula lenta (black birch), Fagus grandifolia (american beech), Pinus resinosa (red pine), Quercus rubra (red oak), Quercus velutina (black oak)
• Release date: 2025
• Language: English
• EML file: knb-lter-hfr.8.30
• DOI: digital object identifier
• EDI: data package
• DataONE: data package
• Related links:
• Project Website
• Study type: long-term measurement
• Research topic: large experiments and permanent plot studies; soil carbon and nitrogen dynamics
• LTER core area: organic matter movement, mineral cycling, disturbance patterns, human-environment interactions
• Keywords: carbon, foliage, litterfall, microbes, microbial biomass, mycorrhizae, nitrogen, plant biomass, soil solution chemistry
• Abstract:

  The purpose of this study is to increase our understanding of ecosystem nitrogen dynamics in response to elevated nitrogen inputs. With atmospheric nitrogen deposition in the Northeastern United States currently at 10 to 20 times above historic background levels, it is possible that excessive nitrogen inputs could saturate the retention capacity of a forest ecosystem. Potential effects of nitrogen saturation include increased nitrate leaching and simultaneous base cation losses, soil acidification, altered fluxes of trace gases and forest decline. Two adjacent stands were chosen for the study: an even-aged red pine (Pinus resinosa Ait.) stand planted in 1926 and a 50-year-old mixed hardwood stand that had regenerated naturally after clearcutting in approximately 1945. The hardwood stand is dominated by black and red oak (Quercus velutina Lam.; Q. rubra L.) with significant amounts of black birch (Betula lenta L.), red maple (Acer rubrum L.) and American beech (Fagus grandifolia Ehrh.). The dominant soil types are stony- to sandy-loams formed from glacial till, and are classified as Typic Dystrochrepts of the Canton or Montauk series. Four treated plots were established within each stand: control, low N, low N plus sulfur (N+S) and high N. Each plot measures 30 x 30 meters (0.09 ha) and is divided into thirty-six 5 x 5 m subplots.

• Methods:

  Fertilization

  Fertilizer additions of NH4NO3 and Na2SO4 began in 1988 as six equal applications over the growing season (May - Sept). Fertilizer is weighed, mixed with 20 liters of water (equivalent to 0.002 cm rainfall) and applied using a backpack sprayer. Na2SO4 applications were discontinued after the 1998 growing season. The hardwood and pine stands each contain four plots, with application rates as follows: Control, Low = 5gN/m^2 per year, High = 15gN/m^2 per year, N+S = 5gN/m^2 + 7.4gS/m^2 per year. Plot designations are P or H followed by C,L,H,NS for control, low, high N+S, respectively. Upon request, more detailed information is available on the exact applications rates based on fertilizer sample analysis.

  Species Codes

  ACPE = striped maple (Acer pensylvanicum L.). ACRU = red maple (Acer rubrum L.). ACSA3 = sugar maple (Acer saccharum Marsh.). BELE = black birch (Betula lenta L.). BEPA = white birch (Betula papyrifera Marsh.). CADE12 = American chestnut (Castanea dentata (Marsh.) Borkh.). FAGR = American beech (Fagus grandifolia Ehrh.). NYSY = black tupelo (Nyssa sylvatica Marsh.). PIAB = Norway spruce (Picea abies (L.) Karst.). PIRE = red pine (Pinus resinosa Aiton). PIRU = red spruce (Picea rubens Sarg.). PIST = white pine (Pinus strobus L.). PRSE2 = black cherry (Prunus serotina Ehrh.). QUAL = white oak (Quercus alba L.). QURU = red oak (Quercus rubra L.). QUVE = black oak (Quercus velutina Lam.). TSCA = Eastern hemlock (Tsuga canadensis (L.) Carr.).

  HF008-01: Foliar Chemistry

  Fresh leaf samples were collected during the first week of August. Needle samples from 20 different red pines in each pine plot were pooled into 5 samples for analysis. Oak, red maple and black birch were sampled in the hardwood plots. A total of four composite samples per species were collected in each plot, with each sample including leaves from the upper canopy, mid-level and understory. Red oak and black oak were combined and labeled as black oak. Samples were dried, ground and scanned for percent nitrogen, lignin and cellulose using an NIRSystems near infrared spectrometer. In selected years, samples were digested and digestate measured for base cations using either ICP (1999, 2002) or DCP (1997 and earlier). This dataset includes percent nitrogen, lignin and cellulose, means and standard deviations for 1988-1999, 2002 and 2005-8.

  Data is described in detail in: Magill, A.H., J.D. Aber, W.S. Currie, K.J. Nadelhoffer, M.E. Martin, W.H. McDowell, J.M. Melillo, P. Steudler. 2004. Ecosystem response to 15 years of chronic nitrogen additions at the Harvard Forest LTER, Massachusetts, USA. Forest Ecology and Management, 196(1):7-28.

  HF008-02: Litter Chemistry

  Aboveground litterfall was collected three times per year on or near June 1, September 1 and November 15 from each of nine litter collection baskets per plot (2.345 x 10-4 m2 in size). Litter samples were sorted by species (red and black oak combined), dried for 48 hours at 70 C, weighed and ground using a Wiley mill with a 1 mm mesh screen. Ground samples were dried overnight at 70 C and analyzed for nitrogen, lignin, and cellulose content using near-infrared (NIR) spectroscopy.

  Data is described in detail in: Magill, A.H., J.D. Aber, W.S. Currie, K.J. Nadelhoffer, M.E. Martin, W.H. McDowell, J.M. Melillo, P. Steudler. 2004. Ecosystem response to 15 years of chronic nitrogen additions at the Harvard Forest LTER, Massachusetts, USA. Forest Ecology and Management, 196(1):7-28.

  HF008-03: Litterfall Biomass

  Total litter mass was measured by collecting annual litterfall in baskets (9 baskets per plot, collected several times per season). Data from some years is available at the species level; data posted here are foliar biomass for all species combined, scaled to g/m^2 for each plot. Currently posted data may be a slight underestimate, since it is based on the species-level collection, and does not include unidentified leaf fragments. Data will be updated to make this correction soon (June 2009). Samples were also ground and scanned for percent nitrogen, lignin and cellulose using an NIRSystems near infrared spectrometer (see HF008-02).

  HF008-04: Tree Inventory

  All trees above 5cm Diameter Breast Height (DBH) were numbered and measured in 1988. In subsequent years, trees previously too small were tagged and measured. In this dataset, we report tree-level DBH measurements. Tree data is reported by subplot - numbered [a-f][[1-6], for a total of 36 5x5m subplots per plot. Note that in some years, some subplots were not sampled (HC-F1, PL-F[1-6]). This is important when scaling tree-level DBH to biomass per unit area. Also note that DBH is listed as 0 for trees not yet large enough for the inventory. DBH is also listed as 0 after the death of a tree. Pine plots are no longer surveyed and marked by “NA” for not sampled.

  For more information on calculating biomass, with suggested sources of allometry, see: Magill, A. H., Aber, J. D., Hendricks, J. J., Bowden, R. D., Melillo, J. M., Steudler, P. A. 1997. Biogeochemical response of forest ecosystems to simulated chronic nitrogen deposition. Ecological Applications 7: 402-415.

  HF008-05: Tension Lysimeters

  In 1988, 5 porous-cup lysimeters were installed in each plot at 60cm depth. Tension of 50psi was drawn for 24 hours prior to collection. Samples were filtered and frozen prior to analysis for NH4 and NO3. Samples were also analyzed for TDN using the TOC-5000 with an Antek chemiluminecent detector. Base cations were measured using either ICP (1998 and later) or DCP (1997 and earlier).

  Data is described in detail in: Magill, A. H., Aber, J. D., Hendricks, J. J., Bowden, R. D., Melillo, J. M., Steudler, P. A. 1997. Biogeochemical response of forest ecosystems to simulated chronic nitrogen deposition. Ecological Applications 7: 402-415.

  HF008-06: Soil CN and Mineralization

  Net nitrification and net mineralization were measured using the in-situ buried bag technique. Three sets of paired cores were taken in each of the 3 designated subplots of each plot (total of 9 paired samples per treatment). Initial samples were analyzed immediately, while in-situ samples were incubated for a period of 4-6 weeks during the growing season, in addition to an overwinter incubation (Nov-Apr). Samples were analyzed for extractable NH4 and NO3 concentrations using a 1N KCl extraction.

  Details on sampling and analysis can be found at: Aber, J. D., Magill, A., Boone, R. D., Melillo, J. M., Steudler, P. A., Bowden, R. D. 1993. Plant and soil responses to three years of chronic nitrogen additions at the Harvard Forest, Petersham, MA. Ecological Applications 3: 156-166.

  HF008-07: Litter Decomposition

  Decomposition rates and N dynamics of foliar litter from 4 tree species were measured over a 72 month period on the Chronic Nitrogen Addition plots at the Harvard Forest, beginning in November 1988. Fresh litterfall was collected in the fall of 1988 on nylon mesh screens which were placed in the experimental stands but outside of the treated plots. Litter was air dried and sorted into red pine, red maple, yellow birch and black oak and approximately 9.5 to 10.0 g placed into 20x20 cm bags made of 1 mm mesh nylon window screening. Litter bags containing red pine and red maple foliage were placed in plots of both the hardwood and pine stands, black oak bags were placed in the hardwood plots only and yellow birch bags in the pine plots only.

  One string of bags (12 bags with 4 replicates of 3 species) was collected from each plot in mid-August and mid-November beginning in 1989 and continuing through 1993. In 1994, two strings were pulled up on each collection date, completing the experiment in November 1994. Mass loss was recorded for individual litterbag samples. Samples were then combined, ground and analyzed for percent nitrogen, lignin, and cellulose using near-infrared spectroscopy.

  For more details see: Magill, AH, and JD Aber. 1998. Long-term effects of experimental nitrogen additions on foliar litter decay and humus formation in forest ecosystems. Plant and Soil 203:301-311.

  HF008-08: Zero Tension Lysimeters

  ZTL's are gravity fed gravel and glass bead filled collection units (0.3 to 1.5cm) located beneath the organic horizon with a tube draining approximately 154 cm2 into a 1 liter bottle. Samples were collected within 1 week following a rain event, weighed, filtered through a 0.7um filter and frozen prior to analysis. N and C were measured in the same manner as tension lysimeters (HF08-05). Base cations were measured using either ICP (1998 and later) or DCP (1997 and earlier).

• 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, Ollinger S. 2025. Chronic Nitrogen Amendment Experiment at Harvard Forest since 1988. Harvard Forest Data Archive: HF008 (v.30). Environmental Data Initiative: https://doi.org/10.6073/pasta/2ab7cead9e0c62579ca66a8085306e08.

Detailed Metadata

hf008-01: foliar chemistry

1. year: year
2. treat: treatment
   • HC: Hardwood Control
   • HH: Hardwood High N
   • HL: Hardwood Low N
   • HS: Hardwood N + Sulfur
   • PC: Pine Control
   • PH: Pine High N
   • PL: Pine Low N
   • PS: Pine N + Sulfur
3. species: species
   • ACPE: striped maple (Acer pensylvanicum L.)
   • ACRU: red maple (Acer rubrum L.)
   • ACSA3: sugar maple (Acer saccharum Marsh.)
   • BELE: black birch (Betula lenta L.)
   • BEPA: white birch (Betula papyrifera Marsh.)
   • CADE12: American chestnut (Castanea dentata (Marsh.) Borkh.)
   • FAGR: American beech (Fagus grandifolia Ehrh.)
   • NYSY: black tupelo (Nyssa sylvatica Marsh.)
   • PIAB: Norway spruce (Picea abies (L.) Karst.)
   • PIRE: red pine (Pinus resinosa Aiton)
   • PIRU: red spruce (Picea rubens Sarg.)
   • PIST: white pine (Pinus strobus L.)
   • PRSE2: black cherry (Prunus serotina Ehrh.)
   • QUAL: white oak (Quercus alba L.)
   • QURU: red oak (Quercus rubra L.)
   • QUVE: black oak (Quercus velutina Lam.)
   • TSCA: Eastern hemlock (Tsuga canadensis (L.) Carr.)
4. n: number
5. av_n: mean of foliar samples measured as percent nitrogen using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
6. sd_n: standard deviation of foliar samples measured as percent nitrogen using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
7. av_lig: mean of foliar samples measured as percent lignin using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
8. sd_lig: standard deviation of foliar samples measured as percent lignin using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
9. av_cel: mean of foliar samples measured as percent cellulose using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
10. sd_cel: standard deviation of foliar samples measured as percent cellulose using near-infrared spectroscopy (unit: dimensionless / missing value: NA)

hf008-02: litter chemistry

1. year: year
2. treat: treatment
   • HC: Hardwood Control
   • HH: Hardwood High N
   • HL: Hardwood Low N
   • HS: Hardwood N + S
   • PC: Pine Control
   • PH: Pine High N
   • PL: Pine Low N
   • PS: Pine N + Sulfur
3. species: species
   • ACPE: striped maple (Acer pensylvanicum L.)
   • ACRU: red maple (Acer rubrum L.)
   • ACSA3: sugar maple (Acer saccharum Marsh.)
   • BELE: black birch (Betula lenta L.)
   • BEPA: white birch (Betula papyrifera Marsh.)
   • CADE12: American chestnut (Castanea dentata (Marsh.) Borkh.)
   • FAGR: American beech (Fagus grandifolia Ehrh.)
   • NYSY: black tupelo (Nyssa sylvatica Marsh.)
   • PIAB: Norway spruce (Picea abies (L.) Karst.)
   • PIRE: red pine (Pinus resinosa Aiton)
   • PIRU: red spruce (Picea rubens Sarg.)
   • PIST: white pine (Pinus strobus L.)
   • PRSE2: black cherry (Prunus serotina Ehrh.)
   • QUAL: white oak (Quercus alba L.)
   • QURU: red oak (Quercus rubra L.)
   • QUVE: black oak (Quercus velutina Lam.)
   • TSCA: Eastern hemlock (Tsuga canadensis (L.) Carr.)
4. n: number
5. av_n: mean of litter samples measured as percent nitrogen using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
6. sd_n: standard deviation of litter samples measured as percent nitrogen using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
7. av_lig: mean of litter samples measured as percent lignin using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
8. sd_lig: standard deviation of litter samples measured as percent lignin using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
9. av_cel: mean of litter samples measured as percent cellulose using near-infrared spectroscopy (unit: dimensionless / missing value: NA)
10. sd_cel: standard deviation of litter samples measured as percent cellulose using near-infrared spectroscopy (unit: dimensionless / missing value: NA)

hf008-03: litterfall biomass

1. plot: plot/treatment
   • PC: Pine Control
   • PL: Pine Low N
   • PNS: Pine N + Sulfur
   • PH: Pine High N
   • HC: Hardwood Control
   • HL: Hardwood Low N
   • HNS: Hardwood N + Sulfur
   • HH: Hardwood High N
2. year: year
3. nbasket: number of litter baskets averaged into annual mean. Nine baskets are located in each plot but sometimes baskets are tipped. (unit: number / missing value: NA)
4. mean: mean litterfall (unit: gramsPerSquareMeter / missing value: NA)
5. sd: standard deviation litterfall (unit: dimensionless / missing value: NA)

hf008-04: tree inventory

1. plot: plot/treatment
   • PC: Pine Control
   • PH: Pine High N
   • PL: Pine Low N
   • PNS: Pine N + Sulfur
   • HC: Hardwood Control
   • HH: Hardwood High N
   • HL: Hardwood Low N
   • HNS: Hardwood N + Sulfur
2. subplot: subplot
3. treetag: tree tag
4. species: species
   • ACPE: striped maple (Acer pensylvanicum L.)
   • ACRU: red maple (Acer rubrum L.)
   • ACSA3: sugar maple (Acer saccharum Marsh.)
   • BELE: black birch (Betula lenta L.)
   • BEPA: white birch (Betula papyrifera Marsh.)
   • CADE12: American chestnut (Castanea dentata (Marsh.) Borkh.)
   • FAGR: American beech (Fagus grandifolia Ehrh.)
   • NYSY: black tupelo (Nyssa sylvatica Marsh.)
   • PIAB: Norway spruce (Picea abies (L.) Karst.)
   • PIRE: red pine (Pinus resinosa Aiton)
   • PIRU: red spruce (Picea rubens Sarg.)
   • PIST: white pine (Pinus strobus L.)
   • PRSE2: black cherry (Prunus serotina Ehrh.)
   • QUAL: white oak (Quercus alba L.)
   • QURU: red oak (Quercus rubra L.)
   • QUVE: black oak (Quercus velutina Lam.)
   • TSCA: Eastern hemlock (Tsuga canadensis (L.) Carr.)
5. dbh_10_1988: diameter at breast height in Oct. 1988 (unit: centimeter / missing value: NA)
6. dbh_11_1990: diameter at breast height in Nov. 1990 (unit: centimeter / missing value: NA)
7. dbh_11_1993: diameter at breast height in Nov. 1993 (unit: centimeter / missing value: NA)
8. dbh_2_1997: diameter at breast height in Feb. 1997 (unit: centimeter / missing value: NA)
9. dbh_03_2000: diameter at breast height in Mar. 2000 (unit: centimeter / missing value: NA)
10. dbh_04_2003: diameter at breast height in Apr. 2003 (unit: centimeter / missing value: NA)
11. dbh_04_2006: diameter at breast height in Apr. 2006 (unit: centimeter / missing value: NA)
12. dbh_10_2008: diameter at breast height in Oct. 2008 (unit: centimeter / missing value: NA)
13. dbh_06_2017: diameter at breast height in June 2017. Pine plots are no longer surveyed and marked by “NA”. (unit: centimeter / missing value: NA)

hf008-05: tension lysimeters

1. year: year
2. date: date
3. plot: plot
4. n_mls: number of samples (unit: number / missing value: NA)
5. avmls: mean volume (unit: milliliter / missing value: NA)
6. sdmls: standard deviation volume (unit: dimensionless / missing value: NA)
7. n_.n: number of samples (unit: number / missing value: NA)
8. avno3: mean NO3 (unit: milligramsPerLiter / missing value: NA)
9. sdno3: standard deviation NO3 (unit: dimensionless / missing value: NA)
10. avnh4: mean NH4 (unit: milligramsPerLiter / missing value: NA)
11. sdnh4: standard deviation NH4 (unit: dimensionless / missing value: NA)

hf008-06: soil CN and mineralization

1. year: year
2. plot: plot/treatment
   • HC: Hardwood Control
   • HH: Hardwood High N
   • HL: Hardwood Low N
   • HNS: Hardwood N + Sulfur
   • PC: Pine Control
   • PH: Pine High N
   • PL: Pine Low N
   • PNS: Pine N + Sulfur
3. min_organic: organic net mineralization NO3-N+NH4-N1 (unit: kilogramsPerHectarePerYear / missing value: NA)
4. min_mineral: mineral net mineralizatiom NO3-N+NH4-N (unit: kilogramsPerHectarePerYear / missing value: NA)
5. min_org_min: total net mineralization NO3-N+NH4-N (unit: kilogramsPerHectarePerYear / missing value: NA)
6. nit_organic: organic net nitrification NO3-N (unit: kilogramsPerHectarePerYear / missing value: NA)
7. nit_mineral: mineral net nitrification NO3-N (unit: kilogramsPerHectarePerYear / missing value: NA)
8. nit_org_min: total net nitrification NO3-N (unit: kilogramsPerHectarePerYear / missing value: NA)

hf008-07: litter decomposition

1. collection: collection number
2. month: month
3. year: year
4. species: species
   • ACPE: striped maple (Acer pensylvanicum L.)
   • ACRU: red maple (Acer rubrum L.)
   • ACSA3: sugar maple (Acer saccharum Marsh.)
   • BELE: black birch (Betula lenta L.)
   • BEPA: white birch (Betula papyrifera Marsh.)
   • CADE12: American chestnut (Castanea dentata (Marsh.) Borkh.)
   • FAGR: American beech (Fagus grandifolia Ehrh.)
   • NYSY: black tupelo (Nyssa sylvatica Marsh.)
   • PIAB: Norway spruce (Picea abies (L.) Karst.)
   • PIRE: red pine (Pinus resinosa Aiton)
   • PIRU: red spruce (Picea rubens Sarg.)
   • PIST: white pine (Pinus strobus L.)
   • PRSE2: black cherry (Prunus serotina Ehrh.)
   • QUAL: white oak (Quercus alba L.)
   • QURU: red oak (Quercus rubra L.)
   • QUVE: black oak (Quercus velutina Lam.)
   • TSCA: Eastern hemlock (Tsuga canadensis (L.) Carr.)
5. plot: plot/treatment
   • HC: Hardwood Control
   • HH: Hardwood High N
   • HL: Hardwood Low N
   • HNS: Hardwood N + Sulfur
   • PC: Pine Control
   • PH: Pine High N
   • PL: Pine Low N
   • PNS: Pine N + Sulfur
6. n_wt: number for percent mass remaining
7. avg_m_remain: mean of litter mass remaining as percent of initial mass (unit: dimensionless / missing value: NA)
8. sd_m_remain: standard deviation of litter mass remaining as percent of initial mass (unit: dimensionless / missing value: NA)
9. n: number of samples analysed with NIRSystems Near Infrared Spectrophotometer for %N
10. avg_per_n: mean of percent nitrogen (unit: dimensionless / missing value: NA)
11. sd_per_n: standard deviation of percent nitrogen (unit: dimensionless / missing value: NA)
12. avg_per_lignin: mean of percent lignin (unit: dimensionless / missing value: NA)
13. sd_per_lignin: standard deviation of percent lignin (unit: dimensionless / missing value: NA)
14. avg_per_cellulose: mean of percent cellulose (unit: dimensionless / missing value: NA)
15. sd_per_cellulose: standard deviation of percent cellulose (unit: dimensionless / missing value: NA)

hf008-08: zero tension lysimeters

1. year: year
2. date: date
3. plot: plot/treatment
   • HC: Hardwood Control
   • HH: Hardwood High N
   • HL: Hardwood Low N
   • HS: Hardwood N + Sulfur
   • PC: Pine Control
   • PH: Pine High N
   • PL: Pine Low N
   • PS: Pine N + Sulfur
4. no3n: nitrate-N (NO3-N) in mg-N/L (unit: milligramsPerLiter / missing value: NA)
5. nh4n: ammonium-N (NH4-N) in mg-N/L (unit: milligramsPerLiter / missing value: NA)
6. din: dissolved inorganic nitrogen (DIN). DIN = (NO3-N + NH4-N) (unit: milligramsPerLiter / missing value: NA)
7. tdn: total dissolved nitrogen(TDN) (unit: milligramsPerLiter / missing value: NA)
8. don: dissolved organic nitrogen(DON. DON = (TDN - DIN) (unit: milligramsPerLiter / missing value: NA)
9. toc: dissolved organic carbon (DOC) in mg-C/L (unit: milligramsPerLiter / missing value: NA)

hf008-09: litterfall since 2003

1. plot: plot/treatment
   • PC: Pine Control
   • PL: Pine Low N
   • PNS: Pine N + Sulfur
   • PH: Pine High N
   • HC: Hardwood Control
   • HL: Hardwood Low N
   • HNS: Hardwood N + Sulfur
   • HH: Hardwood High N
2. year: year
3. nbasket: number of litter baskets averaged into annual mean. Nine baskets are located in each plot but sometimes baskets are tipped. (unit: number / missing value: NA)
4. mean: mean litterfall (unit: gramsPerSquareMeter / missing value: NA)
5. sd: standard deviation litterfall (unit: dimensionless / missing value: NA)
6. note: note

hf008-10: ants 2003

1. date: date
2. treat: treatment town or more specific (Prospect Hill)
   • HC: Hardwood Control
   • HH: Hardwood High N
   • HL: Hardwood Low N
   • HS: Hardwood N + Sulfur
   • PC: Pine Control
   • PH: Pine High N
   • PL: Pine Low N
   • PS: Pine N + Sulfur
3. subfamily: subfamily of specimen
4. ant_genus: genus of specimen
5. ant_species: species of specimen
6. code: six or seven character species code (= first 3 letters of genus + first 3 letters of species + number when the previous six characters are not unique). See hf147-01-species-codes.csv for additional information
7. collection: where specimen is stored (in sample archive)
8. vial: vial number of specimen
9. collector: who collected the specimen: REU students Jonathan Chen, Matt Lau, and David Díaz