The Use of Water and Minerals by Evergreen and Deciduous Shrubs in Okefenokee Swamp

Abstract

Shoot water potentials, leaf diffusion resistances and foliar concentrations of Ca2+, Mg2+, K+, N and P were measured in an evergreen shrub (Lyonia lucida [Lam.] K. Koch) and a deciduous shrub (Clethra alnifolia L.) in Okefenokee Swamp, Georgia [USA]. An upland, evergreen species (L. ferruginea [Walt.] Nutt.) was included for comparison. C. alnifolia generally had the highest mineral contents (percentage of dry weight) and the highest water loss in transpiration. During several 24 h monitoring periods, the lowest observed shoot water potentials (L. lucida, -10.1 bars; C. alnifolia, -12.5 bars and L. ferruginea -17.2 bars) did not suggest physiological drought in the swamp species. Only L. lucida showed any evidence of midday stomatal closure. In this warm-temperate swamp, evergreen species have the potential for greater efficiency of mineral use and productivity, largely due to their leaf longevity. In addition, sclerophyllous tissue is probably useful in defense against herbivores.