PROSPECTS AND LIMITATIONS OF AN ISOTOPE TRACER TECHNIQUE FOR UNDERSTANDING SULFUR CYCLING IN FORESTED AND AGROECOSYSTEMS

Applications of isotopically distinct sulfur compounds have recently b een used for tracing the fate of added sulfur in whole catchments or s ub-compartments therein. Basic principles, the analytical methodology, and data evaluation for this isotope tracer technique are briefly des cribed. We recommend that delta(34)S-values of applied and natural sul fur compounds in the investigated ecosystem should differ by more than 20 parts per thousand, in order to successfully ascertain sulfur flux es. Where possible, a high ratio of applied sulfur loads versus sulfur pool sizes in the ecosystem should also be realized in order to allow the assessment of sulfur transformations in the study area. Prospects and limitations of this isotope tracer technique are critically discu ssed by reviewing results from recently or currently conducted lysimet er and field experiments.