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HERO ID
93806
Reference Type
Journal Article
Title
Inorganic nitrogen losses from a forested ecosystem in response to physical, chemical, biotic, and climatic perturbations
Author(s)
Aber, JD; Ollinger, SV; Driscoll, CT; Likens, GE; Holmes, RT; Freuder, RJ; Goodale, CL
Year
2002
Is Peer Reviewed?
Yes
Journal
Ecosystems
ISSN:
1432-9840
EISSN:
1435-0629
Volume
5
Issue
7
Page Numbers
648-658
Language
English
DOI
10.1007/s10021-002-0203-8
Web of Science Id
WOS:000179275900005
URL
http://dx.doi.org/10.1007/s10021-002-0203-8
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Abstract
#Nitrate leaching to streams is a sensitive indicator of the biogeochemical status of forest ecosystems. Two primary theories predicting long-term (decadal) changes in nitrate loss rates (N saturation theory and the nutrient retention hypothesis) both predict increasing dissolved inorganic nitrogen (DIN) losses for watershed 6 (W6), the biogeochemical reference watershed at the Hubbard Brook Experimental Forest (HBEF). Measured values, however, have declined substantially since measurements began in the mid-1960s. Are these theories wrong, or are there other important controls on DIN losses at the annual to decadal time scale that have obscured the tendency toward higher losses over time? We tested the individual and combined effects of several forms of disturbance on DIN loss rates from northern hardwood forests by comparing predictions from a relatively simple model of forest carbon, nitrogen, and water dynamics (PnET-CN) with the long-term record of annual DIN loss from W6 at HBEF. Perturbations tested include interannual climate variation, changes in atmospheric chemistry (CO2. O3, N deposition), and physical and biotic disturbances (two harvests, a hurricane salvage, and a defoliation event). No single disturbance caused changes in DIN losses to mimic measured values. Only when run with all of the disturbances combined did the model-predicted pattern of interannual change in DIN loss approach the measured record. Single-disturbance simulations allow an estimation of the role of each in the total pattern of DIN loss. We conclude that DIN losses from W6 were elevated in the 1960s by a combination of recovery from extreme drought and a significant defoliation event. N deposition alone, in the absence of other disturbances, would have increased DIN losses by 0.35 g N m(-2)y(-1). These findings indicate that predictions of DIN losses must take into account the full spectrum of disturbance events and changes in environental conditions impacting the systems examined.
Keywords
model; PnET; climate; harvest; defoliation; CO2; ozone; N deposition; nitrate; Hubbard Brook Experimental Forest; streams;NORTHERN HARDWOOD FORESTS; BROOK-EXPERIMENTAL-FOREST; LONG-TERM; NEW-HAMPSHIRE; LAND-USE; STREAMWATER CHEMISTRY; INSECT DEFOLIATION; NUTRIENT BUDGETS; ATMOSPHERIC CO2; SOIL FERTILITY
Tags
•
ISA NOxSOxPM Ecology (2018)
Cited in First Draft
Appendix C: Case Studies
Northeast US
Cited in the Second Draft
Appendix 16
16.1 Northeast
•
ISA NOxSOxPM Ecology (2020- Final Project Page)
Cited
Appendix 16
16.1 Northeast
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