Ca cycling and isotopic fluxes in forested ecosystems in Hawaii
نویسندگان
چکیده
[1] Biogeochemical processes fractionate Ca isotopes in plants and soils along a 4 million year developmental sequence in the Hawaiian Islands. We observed that plants preferentially take up Ca relative to Ca, and that biological fractionation and changes in the relative contributions from volcanic and marine sources produce a significant increase in Ca in soil exchangeable pools. Our results imply moderate fluxes enriched in Ca from strongly nutrient-depleted old soils, in contrast with high Ca fluxes in young and little weathered environments. In addition, biological fractionation controls divergent geochemical pathways of Ca and Sr in the plant-soil system. While Ca depletes progressively with increasing soil age, Sr/Ca ratios increase systematically. Sr isotope ratios provide a valuable tracer for provenance studies of alkaline earth elements in forested ecosystems, but its usefulness is limited when deciphering biogeochemical processes involved in the terrestrial Ca cycle. Ca isotopes in combination with Sr/Ca ratios reveal more complex processes involved in the biogeochemistry of Ca and Sr. Citation: Wiegand, B. A., O. A. Chadwick, P. M. Vitousek, and J. L. Wooden (2005), Ca cycling and isotopic fluxes in forested ecosystems in Hawaii, Geophys. Res. Lett., 32, L11404, doi:10.1029/2005GL022746.
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