Document: STE-3-76-15

Spatial and temporal aspects of water use across the riparian-upalnd gradient in a southern African savanna landscape.

INNIS, S.A.* ¹, K.H.ROGERS ² and R.J.NAIMAN ¹

University of Washington, Seattle, WA 98195 USA ¹
University of the Witwatersrand, Johannesburg, South Africa ²

Abstract:
Riparian systems within the savanna landscape of southern Africa are subject to particularly strong biophysical gradients, which vary in nature and intensity between the monsoonal seasonal cycles of hot wet summers and warm dry winters. Water is thought to be a strong driving factor in these systems; therefore, we investigated water use across the riparian-upland gradient using several species of trees with overlapping but distinct distributions in the landscape. Using natural abundance ratios of deuterium (d D) we show that water utilization is subject to shifts both spatially across the riparian-upland gradient as well as temporally with seasonal changes in precipitation, discharge, and soil moisture. In addition, we investigated water stress and efficiency using measures of d ¹³C, stomatal conductance, and xylem pressure potential. These data demonstrate differences within species across the riparian-upland gradient as well as between species with differing overall distributions.

Keywords: riparian vegetation, savannas, water relations, stable isotopes,

This abstract is being presented at: 8:45 AM in session:
Oral Session #20: Riparian Ecology.