Nitrogen mineralization in O horizon soils during 27 years of nitrogen enrichment at the Bear Brook Watershed in Maine, USA
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Chronic elevated nitrogen (N) deposition has altered the N status of temperate forests, with significant implications for ecosystem function. The Bear Brook Watershed in Maine (BBWM) is a whole paired watershed manipulation experiment established to study the effects of N and sulfur (S) deposition on ecosystem function. N was added bimonthly as (NH4)2SO4 to one watershed from 1989 to 2016, and research at the site has studied the evolution of ecosystem response to the treatment through time. Here, we synthesize results from 27 years of research at the site and describe the temporal trend of N availability and N mineralization at BBWM in response to chronic N deposition. Our findings suggest that there was a delayed response in soil N dynamics, since labile soil N concentrations did not show increases in the treated watershed (West Bear, WB) compared to the reference watershed (East Bear, EB) until after the first 4 years of treatment. Labile N became increasingly available in WB through time, and after 25 years of manipulations, treated soils had 10× more extractable ammonium than EB soils. The WB soils had 200× more extractable nitrate than EB soils, driven by both, high nitrate concentrations in WB and low nitrate concentrations in EB. Nitrification rates increased in WB soils and accounted for ~ 50% of net N mineralization, compared to ~ 5% in EB soils. The study provides evidence of the decadal evolution in soil function at BBWM and illustrates the importance of long-term data to capture ecosystem response to chronic disturbance.
KeywordsNitrogen saturation Ammonium Nitrate Nitrogen mineralization Nitrification Forest soils
We thank Jean D. MacRae, Sarah J. Nelson, Tsutomu Ohno, and Aaron Weiskittel for their input on this manuscript. We are extremely grateful to Cheryl Spencer for her assistance in the laboratory and field, and with data handling. This is a MAFES publication.
This study was supported by grants from the National Science Foundation (DEB-1119709) and the Maine Agriculture and Forest Experiment Station (MAFES).
- Adams, M. B., Kochenderfer, J. N., & Edwards, P. J. (2007). The Fernow Watershed acidification study: Ecosystem acidification, nitrogen saturation and base cation leaching. In P. Brimblecombe, H. Hara, D. Houle, & M. Novak (Eds.), Acid rain—deposition to recovery (pp. 267–273). Dordrecht: Springer.CrossRefGoogle Scholar
- Davidson, E. A., David, M. B., Galloway, J. N., Goodale, C. L., Haeuber, R., Harrison, J. A., et al. (2011). Excess nitrogen in the U.S. environment: trends, risks, and solutions. Issues in Ecology, 15, 1–16.Google Scholar
- Elvir, J. A., Wiersma, G. B., Day, M. E., Greenwood, M. S., & Fernandez, I. J. (2006). Effects of enhanced nitrogen deposition on foliar chemistry and physiological processes of forest trees at the Bear Brook Watershed in Maine. Forest Ecology and Management, 221(1–3), 207–214.CrossRefGoogle Scholar
- Fenn, M. E., Poth, M. A., Terry, J. D., & Blubaugh, T. J. (2005). Nitrogen mineralization and nitrification in a mixed-conifer forest in southern California: controlling factors, fluxes, and nitrogen fertilization response at a high and low nitrogen deposition site. Canadian Journal of Forest Research, 35(6), 1464–1486.CrossRefGoogle Scholar
- Gilliam, F. S., & Adams, M. B. (2011). Effects of nitrogen on temporal and spatial patterns of nitrate in streams and soil solution of a central hardwood forest. International Scholarly Research Network ISRN Ecology.Google Scholar
- Gilliam, F. S., Walter, C. A., Adams, M. B., & Peterjohn, W. T. (2018). Nitrogen (N) dynamics in the mineral soil of a central Appalachian hardwood forest during a quarter century of whole-watershed N additions. Ecosystems, 1–16.Google Scholar
- Groffman, P. M., Driscoll, C. T., Durán, J., Campbell, J. L., Christenson, L. M., Fahey, T. J., et al. (2018). Nitrogen oligotrophication in northern hardwood forests. Biogeochemistry.Google Scholar
- Hart, S. C., Stark, J. M., Davidson, E. A., & Firestone, M. K. (1994). Nitrogen mineralization, immobilization, and nitrification. In W. R. W, A. Scott, P. Bottomley, D. Bezdicek, S. Smith, A. Tabatabai, & A. Wollum (Eds.), Methods of soil analysis: microbiological and biochemical properties (pp. 985–1019). Madison: Soil Science Society of America, Inc..Google Scholar
- Helsel, D. R., Mueller, D. K., & Slack, J. R. (2006). Computer program for the Kendall family of trend tests. U.S. Geological Survey Scientific Investigations Report 2005–5275, 4.Google Scholar
- Hipel, K. W., & McLeod, A. I. (1994). Nonparametric tests for trend detection. In Time series modelling of water resources and environmental systems (pp. 853–938). Amsterdam: Elsevier Science, Ltd..Google Scholar
- Lawrence, G. B., Hazlett, P. W., Fernandez, I. J., Ouimet, R., Bailey, S. W., Shortle, W. C., et al. (2015). Declining acidic deposition begins reversal of forest-soil acidification in the northeastern U.S. and eastern Canada. Environmental Science and Technology, 49(22), 13103–13111.CrossRefGoogle Scholar
- Maine River Flow Advisory Commission. (2018). Maine Cooperative Snow Survey. Maine Emergency Management Agency, http://www.maine.gov/rfac/rfac_snow.shtml.
- Patel, K. F., Nelson, S. J., Spencer, C. J., & Fernandez, I. J. (2018a). Soil temperature record for the Bear Brook Watershed in Maine. PANGAEA. https://doi.org/10.1594/PANGAEA.885860.
- Ross, D. S., Shanley, J. B., Campbell, J. L., Lawrence, G. B., Bailey, S. W., Likens, G. E., et al. (2012). Spatial patterns of soil nitrification and nitrate export from forested headwaters in the northeastern United States. Journal of Geophysical Research: Biogeosciences, 117(1), 1–14.Google Scholar
- Sollins, P., Glassman, C., Paul, E. A., Swanston, C. W., Lajtha, K., Heil, J. W., & Elliott, E. T. (1999). Soil carbon and nitrogen pools and fractions. In G. P. Robertson, D. C. Coleman, C. S. Bledsoe, & P. Sollins (Eds.), Standard soil methods for long-term ecological research (pp. 89–105). New York: Oxford University Press.Google Scholar
- Tatariw, C. (2016). The impact of anthropogenic disturbance on soil microbial community composition and activity: implications for ecosystem function. Ph. D. dissertation. University of Maine. 158 pp.Google Scholar