Determination of foliar Ca/Sr discrimination factors for six tree species and implications for Ca sources in northern hardwood forests

Joel D. Blum, Steven P. Hamburg, Ruth D. Yanai, Mary A. Arthur

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Background and aims: Discrimination during foliar uptake between the alkaline earth elements Ca and Sr must be understood to fully utilize Ca/Sr and 87Sr /86Sr ratios as a monitor of Ca sources to trees. The aim of this study was to determine Ca/Sr discrimination factors [DF = (Ca/Sr plant tissue)/ (Ca/Sr nutrient source)] for six tree species in a northern hardwood forest and use foliar chemistry to consider whether species access measurably different soil reservoirs of Ca and Sr. Methods: This was accomplished by measuring the Ca/Sr and 87Sr /86Sr ratios of foliage from individual tree species in mixed stands and comparing these ratios to those of soil extracts from soil pits co-located at six sites in the White Mountains, New Hampshire (USA). Results: For three species for which DFs have been previously determined, the source of Ca and Sr in foliage can be traced predominantly to recycling of material from organic horizons. Foliar and soil chemistry is consistent with each of the tree species in these six sites deriving Ca and Sr predominantly from the Oie horizon. Thus we can estimate DFs (±1sd) for sugar maple (Acer saccharum Marsh.; 1.16 ± 0.13), yellow birch (Betula alleghaniensis Britt.; 1. 31 ± 0.10), white birch (Betula papyrifera Marsh.; 1.30 ± 0.14), pin cherry (Prunus pensylvanica L. f.; 1.24 ± 0.09), American beech (Fagus grandifolia Ehrh.; 1. 78 ± 0.17) and red maple (Acer rubrum L.; 1.90 ± 0.15). Conclusions: These estimates of discrimination factors allow refinement in the use of Ca/Sr and 87Sr /86Sr ratios of foliage to trace Ca sources to plants.

Original languageEnglish
Pages (from-to)303-314
Number of pages12
JournalPlant and Soil
Issue number1-2
StatePublished - Jul 2012

Bibliographical note

Funding Information:
Acknowledgements We thank A. Klaue and M. Johnson for assistance in the laboratory, A. Dasch for helpful discussions, M. Vadeboncoeur and two anonymous reviewers for comments on the manuscript, and M. Acker and the 2003 soil pit crew for assistance in the field. We appreciate the opportunity provided by the USDA Forest Service Northern Research Station to conduct research in the Bartlett Experimental Forest and elsewhere in the White Mountains National Forest and in particular the cooperation of C. Costello. This study was funded by NSF Grants DEB 0235650 and DEB 9810221, and is part of the NSF-funded Long-Term Ecological Research network (http:// and represents a contribution to the Hubbard Brook Ecosystem Study ( The Hubbard Brook and Bartlett Experimental Forests are operated by the Northern Research Station, USDA Forest Service, Newtown Square, PA.


  • Ca/Sr
  • Calcium
  • Discrimination factor
  • Foliage
  • Soil
  • Sr Sr

ASJC Scopus subject areas

  • Soil Science
  • Plant Science


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