© 1988 Heron Publishing—Victoria, Canada
Autumnal changes of sulfur fractions and the ratio of organic sulfur to total nitrogen in leaves and adjacent bark of eastern
cottonwood, white basswood and actinorhizal black alder
Benoit Côté, Jeffrey O. Dawson and Mark B. David
Department of Forestry, 110 Mumford Hall, 1301 West Gregory Drive, University of Illinois at Urbana-Champaign, Urbana, IL
61801, USA / Received November 9, 1987
Summary
Autumnal changes in organic-S, sulfate-S, total-S and the ratios of organic-S to total-N and sulfate-S to organic-S were followed
in leaves and adjacent bark of actinorhizal (Frankia-nodulated) black alder (Alnus glutinosa (L.) Gaertn.) and eastern cottonwood (Populus deltoides Bartr. ex Marsh.) trees growing on a minespoil site high in extractable soil sulfate, and in black alder and white basswood
(Tilia heterophylla Venten.) trees growing on a prairie-derived soil in Illinois. Organic-S concentrations decreased significantly (P < 0.05) during autumn only in foliage of trees growing on the prairie-derived soil where losses of leaf organic-S were 65%
for black alder and 100% for white basswood. Leaf sulfate concentrations were relatively stable throughout autumn in white
basswood growing on prairie-derived soil and in black alder at both sites. Sulfate-S concentrations in leaves were significantly
(P < 0.05) higher in trees at the minespoil site than in trees growing in the prairie-derived soil (5.1 mg g–1 for the minespoil site and 1.2 mg g–1 for the prairie-derived soil), and in the non-actinorhizal species during late summer. During the autumn, the ratio of organic-S
to total-N doubled in leaves of eastern cottonwood at the minespoil site, but in black alder and white basswood growing on
the prarie-derived soil, it decreased by 60 and 74%, respectively. Organic-S concentrations in bark increased more during
autumn in species unable to fix atmospheric N2, than in black alder. The results suggest that patterns of autumnal translocation of leaf S can be site-dependent and that
leaf S and leaf N are, at least in part, translocated independently in the fall. Black alder and eastern cottonwood seemed
to incorporate sulfate-S readily into organic substances in leaves when grown in soils with a high sulfate content.
