FOLIAR LEACHING, TRANSLOCATION, AND BIOGENIC EMISSION OF S-35 IN RADIOLABELED LOBLOLLY PINES

Foliar leaching, basipetal (downward) translocation, and biogenic emission of sulfur, as traced by 35S, were examined in Pinus taeda. The contribution of dry deposition to sulfate-sulfur (SO4 2--S) concentrations in net throughfall (throughfall SO4 2--S concentration minus that in incident precipitation) was >90%. About half of the summertime SO2 dry deposition flux to the loblolly pines was fixed in the canopy and not subsequently leached by rainfall. 35S losses through biogenic emissions from girdled trees were inferred to be 25-28% of the amount injected. Estimates indicated a range in daily biogenic S emission of 0.1-10 μg/g dry needles. Translocation of 35S to roots in nongirdled trees was 14-25% of the injection. -from Author