Assessing tree ring δ15N of four temperate deciduous species as an indicator of N availability using independent long-term records at the Fernow Experimental Forest, WV
Nitrogen deposition in the northeastern US changed N availability in the latter part of the twentieth century, with potential legacy effects. However, long-term N cycle measurements are scarce. N isotopes in tree rings have been used as an indicator of N availability through time, but there is little verification of whether species differ in the strength of this signal. Using long-term records at the Fernow Experimental Forest in West Virginia, we examined the relationship between soil conditions, including net nitrification rates, and wood δ15N in 2014, and tested the strength of correlation between tree ring δ15N of four species and stream water NO3− loss from 1971 to 2000. Higher soil NO3− was weakly associated with higher wood δ15N across species, and higher soil net nitrification rates were associated with higher δ15N for Quercus rubra only. The δ15N of Liriodendron tulipifera and Q. rubra, but neither Fagus grandifolia nor Prunus serotina, was correlated with stream water NO3−. L. tulipifera tree ring δ15N had a stronger association with stream water NO3− than Q. rubra. Overall, we found only limited evidence of a relationship between soil N cycling and tree ring δ15N, with a strong correlation between the wood δ15N and NO3− leaching loss through time for one of four species. Tree species differ in their ability to preserve legacies of N cycling in tree ring δ15N, and given the weak relationships between contemporary wood δ15N and soil N cycle measurements, caution is warranted when using wood δ15N to infer changes in the N cycle.
KeywordsDendroisotope Wood δ15N Nitrogen deposition Watershed Fernow Experimental Forest
The authors thank Chris Walter, Rachel Arrick, Jessica Graham, Hoff Lindberg, Hannah Hedrick, and Leah Baldinger for their field and laboratory assistance on this study. We also acknowledge the USDA Forest Service staff at the Fernow Experimental Forest for long-term management of the site and support of this project. This work was supported by the Long-Term Research in Environmental Biology (LTREB) program at the National Science Foundation (Grant nos. DEB-0417678 and DEB-1019522) and the WVU Department of Biology and Eberly College of Arts and Sciences.
Author contribution statement
MBB and WTP conceived the idea. MBA maintained and processed long-term N data, and MBB and WTP performed field core and soil collection and laboratory analyses. MBA provided editorial advice, and MBB and WTP analyzed the data and wrote the manuscript.
- Burnham MB, Cumming JR, Adams MB, Peterjohn WT (2017) Soluble soil aluminum alters the relative uptake of mineral nitrogen forms by six mature temperate broadleaf tree species: possible implications for watershed nitrate retention. Oecologia. https://doi.org/10.1007/s00442-017-3955-8 CrossRefPubMedGoogle Scholar
- Craine JM, Elmore AJ, Aidar MPM, Bustamante M, Dawson TE, Hobbie EA, Kahmen A, Mack MC, McLauchlan KK, Michelsen A, Nardoto GB, Pardo LH, Peñuelas J, Reich PB, Schuur EAG, Stock WD, Templer PH, Virginia RA, Welker JM, Wright IJ (2009) Global patterns of foliar nitrogen isotopes and their relationships with climate, mycorrhizal fungi, foliar nutrient concentrations, and nitrogen availability. New Phytol 183(4):980–992CrossRefGoogle Scholar
- Handley LL, Raven JA (1992) The use of natural abundance of nitrogen isotopes in plant physiology and ecology. Plant Cell Environ 15:965–985. https://doi.org/10.1111/j.1365-3040.1992.tb01650.x CrossRefGoogle Scholar
- Högberg P, Johannisson C, Högberg MN (2014) Is the high 15N natural abundance of trees in N-loaded forests caused by an internal ecosystem N isotope redistribution or a change in the ecosystem N isotope mass balance? Biogeochemistry 117:351–358. https://doi.org/10.1007/s10533-013-9873-x CrossRefGoogle Scholar
- Lovett GM, Weathers KC, Arthur MA, Schultz JC (2004) Nitrogen cycling in a northern hardwood forest: do species matter? Biogeochemistry 67:289–308. https://doi.org/10.1023/B:BIOG.0000015786.65466.f5 CrossRefGoogle Scholar
- Martinelli LA, Piccolo MC, Townsend AR et al (1999) Nitrogen stable isotopic composition of leaves and soil: tropical versus temperate forests. Biogeochemistry 46:45–65Google Scholar
- National Atmospheric Deposition Program (NADP) (2016) NADP Program Office, Wisconsin State Laboratory of Hygiene, 465 Henry Mall, Madison, WI 53706Google Scholar
- Pardo LH, Nadelhoffer KJ (2012) Using nitrogen isotope ratios to assess terrestrial ecosystems at regional and global scales. In: West JB, Bowen GJ, Dawson TE, Tu KP (eds) Isoscapes. Springer, Dordrecht, pp 221–249Google Scholar
- R Core Team (2018) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/
- Templer PH, Dawson TE (2004) Nitrogen uptake by four tree species of the Catskill Mountains, New York: implications for forest N dynamics. Plant Soil 262:251–261. https://doi.org/10.1023/B:PLSO.0000037047.16616.98 CrossRefGoogle Scholar