uid=HFR,o=lter,dc=ecoinformatics,dc=org all public read doi:10.6073/pasta/646d946be7b6123521e6dce7711534fe Serita Frey https://orcid.org/0000-0002-9221-5919 Scott Ollinger https://orcid.org/0000-0001-6226-1431 Michelle Day Researcher Richard MacLean Researcher Mary Martin Researcher 2026 English

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.

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.).

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.

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.

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).

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.

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.

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.

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.

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).

Harvard Forest

324 North Main Street Petersham MA 01366 USA

(978) 724-3302 (978) 724-3595 https://harvardforest.fas.harvard.edu https://ror.org/059cpzx98 pointOfContact 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. National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210. hf008-01-foliage.csv foliar chemistry hf008-01-foliage.csv 11632 c4d3739703aef983387423c9c7e3a04b 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-01-foliage.csv year year YYYY 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 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.) n number number av_n mean of foliar samples measured as percent nitrogen using near-infrared spectroscopy dimensionless 0.01 real NA missing value sd_n standard deviation of foliar samples measured as percent nitrogen using near-infrared spectroscopy dimensionless 0.01 real NA missing value av_lig mean of foliar samples measured as percent lignin using near-infrared spectroscopy dimensionless 0.01 real NA missing value sd_lig standard deviation of foliar samples measured as percent lignin using near-infrared spectroscopy dimensionless 0.01 real NA missing value av_cel mean of foliar samples measured as percent cellulose using near-infrared spectroscopy dimensionless 0.01 real NA missing value sd_cel standard deviation of foliar samples measured as percent cellulose using near-infrared spectroscopy dimensionless 0.01 real NA missing value 241 hf008-02-litter.csv litter chemistry hf008-02-litter.csv 11833 acac1f1a56d5581e09ff85f132016ea1 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-02-litter.csv year year YYYY 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 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.) n number number av_n mean of litter samples measured as percent nitrogen using near-infrared spectroscopy dimensionless 0.001 real NA missing value sd_n standard deviation of litter samples measured as percent nitrogen using near-infrared spectroscopy dimensionless 0.001 real NA missing value av_lig mean of litter samples measured as percent lignin using near-infrared spectroscopy dimensionless 0.001 real NA missing value sd_lig standard deviation of litter samples measured as percent lignin using near-infrared spectroscopy dimensionless 0.001 real NA missing value av_cel mean of litter samples measured as percent cellulose using near-infrared spectroscopy dimensionless 0.001 real NA missing value sd_cel standard deviation of litter samples measured as percent cellulose using near-infrared spectroscopy dimensionless 0.001 real NA missing value 226 hf008-03-litterfall-until-2002.csv litterfall biomass hf008-03-litterfall-until-2002.csv 2602 e1725abe88e85f40073d7513664f55d5 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-03-litterfall-until-2002.csv 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 year year YYYY nbasket number of litter baskets averaged into annual mean. Nine baskets are located in each plot but sometimes baskets are tipped. number 1 whole NA missing value mean mean litterfall gramsPerSquareMeter 0.1 real NA missing value sd standard deviation litterfall dimensionless 0.01 real NA missing value 112 hf008-04-tree.csv tree inventory hf008-04-tree.csv 73134 82939d70b12dcf2fe64e48cd36f32dd7 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-04-tree.csv 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 subplot subplot subplot treetag tree tag tree tag 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.) dbh_10_1988 diameter at breast height in Oct. 1988 centimeter 0.1 real NA missing value dbh_11_1990 diameter at breast height in Nov. 1990 centimeter 0.1 real NA missing value dbh_11_1993 diameter at breast height in Nov. 1993 centimeter 0.1 real NA missing value dbh_2_1997 diameter at breast height in Feb. 1997 centimeter 0.1 real NA missing value dbh_03_2000 diameter at breast height in Mar. 2000 centimeter 0.1 real NA missing value dbh_04_2003 diameter at breast height in Apr. 2003 centimeter 0.1 real NA missing value dbh_04_2006 diameter at breast height in Apr. 2006 centimeter 0.1 real NA missing value dbh_10_2008 diameter at breast height in Oct. 2008 centimeter 0.1 real NA missing value dbh_06_2017 diameter at breast height in June 2017. Pine plots are no longer surveyed and marked by “NA”. centimeter 0.1 real NA missing value dbh_10_2023 diameter at breast height in October 2023. Pine plots are no longer surveyed and marked by “NA”. centimeter 0.1 real NA missing value 1340 hf008-05-lysimeter.csv tension lysimeters hf008-05-lysimeter.csv 55307 fbd83665ffba031ddd576e5b46413443 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-05-lysimeter.csv year year YYYY date date YYYY-MM-DD plot plot plot n_mls number of samples number 1 whole NA missing value avmls mean volume milliliter 0.1 real NA missing value sdmls standard deviation volume dimensionless 0.01 real NA missing value n_.n number of samples number 1 whole NA missing value avno3 mean NO3 milligramsPerLiter 0.001 real NA missing value sdno3 standard deviation NO3 dimensionless 0.01 real NA missing value avnh4 mean NH4 milligramsPerLiter 0.001 real NA missing value sdnh4 standard deviation NH4 dimensionless 0.001 real NA missing value 1157 hf008-06-CN-min.csv soil CN and mineralization hf008-06-CN-min.csv 1810 3fa2158b75bec6cd20f94781f97c7faa 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-06-CN-min.csv year year YYYY 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 min_organic organic net mineralization NO3-N+NH4-N1 kilogramsPerHectarePerYear 0.01 real NA missing value min_mineral mineral net mineralizatiom NO3-N+NH4-N kilogramsPerHectarePerYear 0.01 real NA missing value min_org_min total net mineralization NO3-N+NH4-N kilogramsPerHectarePerYear 0.01 real NA missing value nit_organic organic net nitrification NO3-N kilogramsPerHectarePerYear 0.01 real NA missing value nit_mineral mineral net nitrification NO3-N kilogramsPerHectarePerYear 0.01 real NA missing value nit_org_min total net nitrification NO3-N kilogramsPerHectarePerYear 0.01 real NA missing value 40 hf008-07-decomp.csv litter decomposition hf008-07-decomp.csv 14155 e29c47b7bfa3d7387e2b817f7a76871c 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-07-decomp.csv collection collection number collection number month month month year year YYYY 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.) 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 n_wt number for percent mass remaining number for percent mass remaining avg_m_remain mean of litter mass remaining as percent of initial mass dimensionless 0.01 real NA missing value sd_m_remain standard deviation of litter mass remaining as percent of initial mass dimensionless 0.01 real NA missing value n number of samples analysed with NIRSystems Near Infrared Spectrophotometer for %N number of samples avg_per_n mean of percent nitrogen dimensionless 0.01 real NA missing value sd_per_n standard deviation of percent nitrogen dimensionless 0.01 real NA missing value avg_per_lignin mean of percent lignin dimensionless 0.01 real NA missing value sd_per_lignin standard deviation of percent lignin dimensionless 0.01 real NA missing value avg_per_cellulose mean of percent cellulose dimensionless 0.01 real NA missing value sd_per_cellulose standard deviation of percent cellulose dimensionless 0.01 real NA missing value 216 hf008-08-ZTL.csv zero tension lysimeters hf008-08-ZTL.csv 30605 a246fe145f04f701fd8152fe94426210 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-08-ZTL.csv year year YYYY date date YYYY-MM-DD 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 no3n nitrate-N (NO3-N) in mg-N/L milligramsPerLiter 0.01 real NA missing value nh4n ammonium-N (NH4-N) in mg-N/L milligramsPerLiter 0.01 real NA missing value din dissolved inorganic nitrogen (DIN). DIN = (NO3-N + NH4-N) milligramsPerLiter 0.01 real NA missing value tdn total dissolved nitrogen(TDN) milligramsPerLiter 0.01 real NA missing value don dissolved organic nitrogen(DON. DON = (TDN - DIN) milligramsPerLiter 0.01 real NA missing value toc dissolved organic carbon (DOC) in mg-C/L milligramsPerLiter 0.01 real NA missing value 637 hf008-09-litterfall-since-2003.csv litterfall since 2003 hf008-09-litterfall-since-2003.csv 2762 05ff8f82de169134aa9ae75c09c46de7 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-09-litterfall-since-2003.csv 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 year year YYYY nbasket number of litter baskets averaged into annual mean. Nine baskets are located in each plot but sometimes baskets are tipped. number 0.1 real NA missing value mean mean litterfall gramsPerSquareMeter 0.01 real NA missing value sd standard deviation litterfall dimensionless 0.01 real NA missing value note note note 108 hf008-10-ants2003.csv ants 2003 hf008-10-ants2003.csv 18183 e60cde855ef50f6f0aa76cb4a8239937 1 \r\n column , https://harvardforest.fas.harvard.edu/data/p00/hf008/hf008-10-ants2003.csv date date YYYY-MM-DD 1 day NA missing value 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 NA missing value subfamily subfamily of specimen subfamily of specimen NA missing value ant_genus genus of specimen genus of specimen NA missing value ant_species species of specimen species of specimen NA missing value 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 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 NA missing value collection where specimen is stored (in sample archive) where specimen is stored (in sample archive) NA missing value vial vial number of specimen vial number of specimen NA missing value collector who collected the specimen: REU students Jonathan Chen, Matt Lau, and David Díaz who collected the specimen: REU students Jonathan Chen, Matt Lau, and David Díaz NA missing value 235 plot soil long-term measurement https://www.chronicn.unh.edu/