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Tracers of Calcium in a Forest Ecosystem: Ca/Sr and Ca IsotopesEPA Grant Number: FP916388
Title: Tracers of Calcium in a Forest Ecosystem: Ca/Sr and Ca Isotopes
Investigators: Hoff, Claire J.
Institution: University of New Hampshire - Main Campus
EPA Project Officer: Graham, Karen
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $111,344
RFA: STAR Graduate Fellowships (2004) RFA Text | Recipients Lists
Research Category: Fellowship - Terrestrial Ecology and Ecosystems , Academic Fellowships , Ecological Indicators/Assessment/Restoration
Calcium is an important base cation within ecosystems, as well as an essential plant nutrient, and is sensitive to anthropogenic influences such as acid rain. The extent to which calcium leaching can be counteracted by release from mineral weathering within the soil is an important, but unanswered question. Determining the fluxes and their respective magnitudes requires a tool to track calcium as it moves through the forest ecosystem. The first objective of this research project is to investigate the reliability of calcium to strontium ratios as tracers of calcium. Preliminary results show that these elements are biologically fractionated, indicating that more caution should be used in assuming that the elemental ratio is conservative. Therefore, the second objective of this research project is to examine the potential use of calcium isotope signatures as a method of tracing cycled calcium.
Ca/Sr and Ca isotope values will be measured in tree tissues (needle and root), substrate leachate, and nutrient solutions from a culture study. Scots pines, Pinus sylvestris were grown in Perlite with the following variables controlled: N supply rate, N species, presence/absence of mycorrhizal fungi, and species of mycorrhizal fungi (including Suillus luteus,Thelephora terrestris, Suillus bovinus , and Laccaria laccata). Data from this culture study then will be combined to create a mass balance of Ca, Sr, and Ca isotopes within the substrate-tree cycle. These cycling data will help to clarify the factors contributing to both elemental and isotopic fractionation. Fractionation specifics, such as magnitude and location (e.g., within tree and during mycorrhizal-tree uptake), can then be used to evaluate the usefulness and accuracy of the particular ratio in tracing Ca. Field samples also will be analyzed to test the tracers under more natural conditions and to provide comparison data so that the effects of environmental stresses on fractionation and cycling can be considered.