Site-level importance of broadleaf deciduous trees outweighs the legacy of high nitrogen (N) deposition on ecosystem N status of Central Appalachian red spruce forests
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Background and aims
Atmospheric nitrogen (N) deposition can influence forest ecosystem N status, and the resilience of forests to the effects of N deposition depends on a number of co-occurring environmental factors that regulate N retention or loss. In this study, we test the idea that N deposition may have important and long-lasting impacts on patterns of N cycling by using field and laboratory techniques to assess N status in seven high-elevation Central Appalachian red spruce (Picea rubens Sarg.) forests located at sites that historically received moderate to high inputs of N atmospheric deposition.
During 2011 and 2012, we measured multiple indices of N availability (e.g. foliar/soil C:N and δ15N, resin ion-exchange, and N transformation rates) that integrate N cycling over seasonal to decadal time scales. Using a model selection approach, we compared the strength of the association between various environmental factors and temporally-integrated indices of N status in a series of regression models.
Site-level differences in the relative importance value of broadleaf deciduous (BD) trees consistently explained most of the observed variation in N status. Soil C:N was significantly lower for sites with greater BD importance (R 2 = 0.67–0.77), and there was a strong positive relationship between BD importance and soil δ15N content (R 2 = 0.64–0.85). Despite a four-fold difference in historic deposition across the seven forest sites, we did not observe any significant relationships between site N status and N deposition.
These findings suggest that potential legacy effects of N deposition were obscured by the influence of BD importance on N status at these sites. Our results add strong support to the idea that predicting the resilience of forests to the effects of N deposition requires detailed knowledge on the contribution of tree species composition to soil N cycling and retention.
KeywordsNitrogen N deposition N availability Broadleaf deciduous trees Red spruce
We would like to thank Amy Hessl, Bradley Breslow, and Benjamin Hedin for assistance with site selection and fieldwork. In addition, we thank the US Forest Service and, in particular, Stephanie Connolly and Kent Karriker for granting us access to these sites to perform fieldwork. Finally we would like to thank Edward Brzostek for his helpful comments and critiques on an earlier draft of this manuscript. This work was supported by the WVU Office of the Dean’s Awards for Research Team Scholarship (ARTS), the WVU Research Corporation’s Program to Stimulate Competitive Research (PSCoR), and in part by the National Science Foundation Research Experience for Undergraduates (NSF-REU) program.
- Burnham KP, Anderson DR (2002) Model selection and multi-model inference: a practical information-theoretic approach. Springer-VerlagGoogle Scholar
- Clarkson RB (1964) Tumult on the Mountains: Lumbering in West Virginia 1770–1920. McClain Printing CompanyGoogle Scholar
- Finzi AC, Breemen NV, Canham CD (1998) Canopy tree-soil interactions within temperate forests: species effects on soil carbon and nitrogen. Ecol Appl 8:440–446Google Scholar
- Hopkins AD (1899) Report on investigations to determine the cause of unhealthy conditions of the spruce and pine from 1880–1893. WV Agricultural Experimental Station. Fairmont Index Steam Print, MorgantownGoogle Scholar
- Johnson AH, McLaughlin SB (1986) In: Gibson J (ed) The nature and timing of the deterioration of red spruce in the northern Appalachian Mountains. National Academy Press, Washington, DC, pp 200–230Google Scholar
- Kelly CN (2010) Carbon and nitrogen cycling in watersheds of contrasting vegetation types in the Fernow Experimental Forest, West Virginia. PhD Dissertation, Virginia TechGoogle Scholar
- Lewis RL (1998) Transforming the Appalachian Countryside: railroads, deforestation, and social change in West Virginia, 1880–1990. University of North Carolina PressGoogle Scholar
- Nadelhoffer KJ, Fry B (1994) Nitrogen isotope studies in forest ecosystems. In: Lajtha K, Michener RJ (eds) Stable isotopes in ecology and environmental science, 2nd edn. Blackwell Scientific Publications, Oxford, pp 22–44Google Scholar
- Nadelhoffer KJ, Aber JD, Melillo JM (1985) Fine roots, net primary production, and soil nitrogen availability: a new hypothesis. 66:1377–1390Google Scholar
- National Atmospheric Deposition Program (2014) Total deposition maps. Version 2014.02. http://nadp.sws.uiuc.edu/committees/tdep/tdepmaps. Accessed 19 March 2015
- Nowacki G, Wendt D (2010) The current distribution, predictive modeling, and restoration potential of red spruce in West Virginia. Proc Confe Ecol Manag High-Elevation Forest Central Southern Appalachian Mountains. USDA-FS Northern Research Station, Slatyfork, WV 163–178Google Scholar
- Ollinger SV, Smith ML, Martin ME, Hallett RA, Goodale CL, Aber JD (2002) Regional variation in foliar chemistry and N cycling among forests of diverse history and composition. Ecology 83:339–355Google Scholar
- Pardo LH, Schaberg PG, McNulty SG (1998) Response of natural abundance of 15N in spruce foliage to chronic N addition. Proc 83rd Ann Meet Ecol Soc America, Baltimore, MD 105Google Scholar
- Pollard JH (1971) On distance estimators of density in randomly distributed forests. Biometrics 991–1002Google Scholar
- Prasad AM, Iverson LR, Matthews S, Peters M (2007) A climate change Atlas for 134 forest tree species of the Eastern United States [Database]. Northern Research Station. USDA Forest Service, DelawareGoogle Scholar
- PRISM Climate Group, Oregon State University (2015) http://prism.oregonstate.edu
- SAS Institute (2003) SAS-JMP version 10.0. SAS Institute, CaryGoogle Scholar
- Stokes MA, Smiley TL (1996) An introduction to tree-ring dating. University of Arizona Press, TusconGoogle Scholar