NITROGEN-FERTILIZATION EFFECTS ON FOLIAR NUTRIENT DYNAMICS AND AUTUMNAL RESORPTION IN MAIDENHAIR TREE (GINGKO-BILOBA L)

We quantified seasonal foliar nutrient dynamics and autumnal N and P r esorption of individuals of the deciduous gymnosperm Gingko biloba (ma idenhair tree) growing in compacted, urban soils over two years follow ing a single fertilization with 150 kg/ha/yr of N (and no P). Mean fol iar nutrient concentrations were more similar to those reported for an giosperm trees than for other gymnosperms. During the autumn following fertilization; 46% and 48 of foliar N and P were resorbed, respective ly; during the second year both increased significantly, to 68% of fol iar N and 74% of foliar P. Absolute N resorption was also greater duri ng the second year, whereas absolute P resorption did not differ signi ficantly between years. During the second year, the level of N resorpt ion rates was similar to that reported for Larix laricina (larch or ta marack), a needle-leafed, deciduous gymnosperm, and greater than those reported for broad-leafed deciduous angiosperms. The level of 1992 P resorption was similar to those reported for a wide range of gymnosper ms and greater than those reported for most angiosperms. N fertilizati on allowed Gingko trees to maintain typical foliar N dynamics even dur ing a persistent drought during which foliar P dynamics were significa ntly altered.