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Harvard Forest Data Archive

HF218

Litter Decomposition in Response to Nitrogen Addition and Soil Warming at Harvard Forest since 2012

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Data

Overview

  • Lead: Serita Frey, Anne Pringle
  • Investigators: Eric Morrison, Christopher Sthultz, Linda van Diepen
  • Contact: Serita Frey
  • Start date: 2010
  • End date: 2012
  • Status: completed
  • Location: Prospect Hill Tract (Harvard Forest), Slab City Tract (Harvard Forest)
  • Latitude: +42.48 to +42.54
  • Longitude: -72.18
  • Elevation: 295 to 385 meter
  • Taxa:
  • Release date: 2014
  • Revisions:
  • EML file: knb-lter-hfr.218.4
  • DOI: digital object identifier
  • Related links:
  • Study type: short-term measurement
  • Research topic: large experiments and permanent plot studies; soil carbon and nitrogen dynamics
  • LTER core area: organic matter, disturbance
  • Keywords: decomposition, litter, nitrogen, soil warming
  • Abstract:

    The purpose of this study is to examine whether two environmental change stressors (warming and nitrogen deposition) differentially impact litter decomposition. We investigated this using a two year litterbag decomposition experiment at the chronic N amendment experiment and the Barre Woods Soil warming experiment, and measured litter decay dynamics, enzyme activities and litter chemistry.

    In both years mass loss of the mixed litter was suppressed under N addition, with most of the mass loss observed in the first year compared to the second year (70% and 30% of total mass loss, respectively). Both years showed either increased activity for some hydrolytic enzymes (e.g. cellobiohydrolase) or no difference (e.g. ß-N-acetylglucosaminidase) with increased N. The lignolytic enzymes (e.g. peroxidases) showed no difference in activity in the first year, but had a highly reduced activity in year 2 under elevated N conditions. Soil warming did not significantly affect litter mass loss, and only had an effect on the activity of a few enzymes.

    In the oak reciprocal litterbag study, decay of oak litter originating from the highest N addition plot was negatively affected by simulated N deposition in the first year of decomposition, while after two years, simulated N deposition negatively affected all litter, and litter originating from the highest N addition plot decayed more slowly than control litter even without added N (i.e. in the control plot). In addition, in the first year of decomposition lignolytic enzyme activities were suppressed in litter originating from the N addition treatments, but due to simulated N deposition in year two.

  • Methods:

    Overview

    Litter was collected in litter traps placed in each of the three N treatment plots of the chronic N amendment experiment and in the control plot of the Barre Woods Soil warming experiment during leaf abscission in the fall of 2010. The collected litter was air-dried and sorted by species, stems were removed, and litter was cut into approximately 3 cm x 3 cm pieces. Litterbags (20 cm x 20 cm) were made of 0.3mm nylon mesh and filled with 10 g of air-dried litter. Each bag was sewn closed, the litter spread evenly within the bag. At the Barre Woods experiment we used mixed litter, representative of the litter fall composition at the BW site. At the Chronic N amendment experiment we implemented two different sets of litterbags; 1) mixed litter (representative of the litter fall composition at the N site), and 2) an ‘oak only’ litterbag experiment, which is a reciprocal litter transplant study using oak litter collected from each of the three N addition plots.

    In fall of 2010, two replicate bags of each litter type (mixed litter or oak litter, see data file for more info) were placed in five to ten subplots of the CNA or BW experiments. The bags were placed on top of the forest floor, beneath the recent litter fall, and pinned to the ground with two U-shaped gardener’s pins.

    At harvest (fall 2011 and fall 2012), litter and other debris attached to the outside of the bags was removed, and wet weight of the bag was recorded. Immediately after collection, a ~2 g subsample was collected from each bag in the field and flash frozen in liquid N or stored in RNA later for fungal community analysis. Then, the remainder of each bag was placed in ziplock bag, placed on ice and transported to the University of New Hampshire, where it was stored at 4°C until further processing. Within three days after harvest, the litter was removed from the harvested bags, and subsampled for subsequent analyses. Subsamples (~ 1 g) were oven-dried (60°C for 48 hours) to determine moisture content and ashed (5 hours at 450°C) to assess potential mineral contamination. Another 1 g subsample was stored at 4°C for enzyme assays and the remaining litter was frozen at -80°C, freeze-dried, ground, and analyzed for C, N, lignin and cellulose concentrations.

    Litter Enzyme Activities

    Activities of the hydrolytic enzymes cellobiohydrolase (CBH), acid phosphatase (PHOS), N-acetyl-ß-glucosaminidase (NAG), and ß-glucosidase (BG) were assayed using the methylumbelliferyl-(MUB) linked substrates (200µM) ß-D-cellobioside, phosphate, N-acetyl-ß-D-glucosaminide, and β-D-glucopyranoside, respectively. The hydrolytic enzyme leucine aminopeptidase (LAP) was assayed using a 7-amido-4-methylcoumarin (AMC)-linked substrate L-Leucine (200µM). Activities of oxidative enzymes phenol oxidases (OX1 and OX2), and peroxidases (PER1 and PER2), were assayed using the substrates L-3,4-dihydroxyphenylalanine (L-DOPA, 25mM), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS, 3mM), L-DOPA+H2O2 (0.3% hydrogen peroxide), and 3,3',5,5'-Tetramethylbenzidine (TMB + H2O2), respectively.

    Briefly, ~0.5 g of field-moist litter was homogenized in 125 ml sodium acetate buffer (50mM, pH = 4.7, average pH of the litter) for 30 seconds using a Magic Bullet (Homeland Housewares LLC). Sample homogenate (200 µl) was transferred to 96-well microplate, followed by addition of 50 µl substrate. Microplates were incubated for 15 min to 18 hours, depending on the enzyme substrate. After incubation, fluorescence was measured at excitation wavelength of 360 nm and an emission wavelength of 450 nm (hydrolytic enzymes) and absorbance was measured at 450nm (OX1, PER1, PER2) or 420nm (OX2) on a Biotek HT plate reader (Biotek, Winooski, USA). All enzyme assays were done with eight or sixteen replicate wells per sample, and corrected for background fluorescence or absorbance of substrate (negative control). For hydrolytic enzymes, the conversion of fluorescence was based on a standard line of the reference standard MUB (BG, CBH, NAG, PHOS) or AMC (LAP). Conversion of OX1 and PER1 was determined based on an empirically determined extinction coefficient of 7.9 μmole-1 used in other studies. Conversion of PER2 (TMB substrate), and OX2 (ABTS substrate) was determined based on an empirically determined extinction coefficient of ε450= 59,000 M-1 cm-1, and ε420=36,000 M-1 cm-1 respectively. Final enzyme activity was expressed as µmol of substrate converted per hour per g litter dry mass (µmol h-1 g-1).

    Litter Chemistry

    Litter C and N concentrations were measured by dry combustion using a CN Analyzer (Perkin Elmer 2400 Series II). Lignin and cellulose concentrations were analyzed at Cumberland Valley Analytical Services (Hagerstown, Maryland, USA) using the acid detergent fiber (ADF) procedure.

  • 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, Pringle A. 2014. Litter Decomposition in Response to Nitrogen Addition and Soil Warming at Harvard Forest since 2012. Harvard Forest Data Archive: HF218.

Detailed Metadata

hf218-01: litter decomposition

  1. id: litterbag identification number. Odd numbers were harvested in year one, even numbers were harvested in year two.
  2. start.date: date that litterbag was harvested from the field
  3. harvest.date: date that litterbag was harvested from the field
  4. days: number of days that litterbag was out in the field decomposing (unit: number / missing value: NA)
  5. site: experiment code
    • CNA: chronic nitrogen amendment experiment
    • BW: barre woods soil warming experiment
  6. treatment: treatment code
    • CN: control nitrogen (0 kg N per ha per year)
    • LN: low nitrogen (50 kg N per ha per year)
    • HN: high nitrogen (150 kg N per ha per year)
    • CW: control warming (no heating, ambient temperature)
    • HW: heated warming (5C above ambient temperature)
  7. plot: plot ID where bag was placed within the SITE
  8. litter: code for treatment where litter in litterbag originated from and litter type
    • mixedCN: litter originating from the CN treatment (TRT): 8.5 g oak (Quercus velutina and rubra), 1.5 g other species; red and striped maple (Acer rubrum and pennsylvanicum), black birch (Betula lenta), and American beech (Fagus grandifolia)
    • mixedCW: litter originating from the CW treatment (TRT): 7 g oak (Quercus velutina and rubra), 2g maple (Acer rubrum and pennsylvanicum),1 g other species; black birch (Betula lenta), and American beech (Fagus grandifolia)
    • oakCN: litter originating from the CW treatment (TRT): 7 g oak (Quercus velutina and rubra), 2g maple (Acer rubrum and pennsylvanicum),1 g other species; black birch (Betula lenta), and American beech (Fagus grandifolia)
    • oakLN: oak (Quercus velutina & rubra) litter originating from the LN treatment
    • oakHN: oak (Quercus velutina & rubra) litter originating from the HN treatment
  9. moist: percentage moisture in litter at harvest date (unit: dimensionless / missing value: NA)
  10. mass.loss: percentage mass loss over the period (DAYS) that bag was out in the field (unit: number / missing value: NA)
  11. decay: decay rate (k) calculated based on first order exponential decay function (y = e-kt), where y is percentage mass remaining at a time point, and t is time in years since decomposition start. (unit: dimensionless / missing value: NA)
  12. n.per: percentage nitrogen in litter at harvest (unit: dimensionless / missing value: NA)
  13. c.per: percentage carbon in litter at harvest (unit: dimensionless / missing value: NA)
  14. cn: carbon to nitrogen ratio in litter at harvest (unit: dimensionless / missing value: NA)
  15. lap: leucine aminopeptidase activity measured in litter at harvest (unit: nanomolesPerGramPerHour / missing value: NA)
  16. cbh: cellobiohydrolase activity measured in litter at harvest (unit: nanomolesPerGramPerHour / missing value: NA)
  17. bg: ß-glucosidase activity measured in litter at harvest (unit: nanomolesPerGramPerHour / missing value: NA)
  18. phos: acid phosphatase activity measured in litter at harvest (unit: nanomolesPerGramPerHour / missing value: NA)
  19. nag: N-acetyl-ß-glucosaminidase activity measured in litter at harvest (unit: nanomolesPerGramPerHour / missing value: NA)
  20. ox1: phenol oxidase activity measured in litter at harvest using L-DOPA as substrate (unit: micromolesPerGramPerHour / missing value: NA)
  21. ox2: phenol oxidase activity measured in litter at harvest using ABTS as substrate (unit: micromolesPerGramPerHour / missing value: NA)
  22. per1: gross peroxidases activity measured in litter at harvest using (L-DOPA+ H2O2 as substrate (unit: micromolesPerGramPerHour / missing value: NA)
  23. per2: peroxidase activity measured in litter at harvest using TMB + H2O2 as substrate (unit: micromolesPerGramPerHour / missing value: NA)
  24. adf: acid Detergent Fiber concentration in litter at harvest (unit: dimensionless / missing value: NA)
  25. lignin: lignin concentration in litter at harvest (unit: dimensionless / missing value: NA)
  26. cellulose: cellulose concentration in litter at harvest (unit: dimensionless / missing value: NA)