Water Relations of Plant Species in the Wet Coastal Tundra at Barrow, Alaska

Abstract

Various aspects of the water relations of six species (Arctophila fulva, Dupontia fischeri, Carex aquatilis, Eriophorum angustifolium, Potentilla hyparctica, and Salix pulchra) characteristic of the wet, coastal tundra near Barrow, Alaska, were measured during the summers of 1972 and 1973 to examine the hypothesis that water stress may increase stomatal resistance and inhibit photosynthesis. A simulation model of internal water status was constructed to examine this hypothesis. The slopes of the leaf water potential vs. relative saturation deficit (RSD) curves were between –0.6 and 1.8 bars RSD^–1. The minimum leaf resistances were between 1 and 3 sec cm^–1 for all species but A. fulva which was 6 sec cm^–1. The relationship between leaf resistance and leaf water potential differed by habitat; species from more moist habitats exhibited stomatal closure at higher leaf water potentials and less control over water loss as the point of stomatal closure was reached than species from drier and more varied habitats. Root resistances to water absorption for D. fischeri, C. aquatilis, and E. angustifolium were independent of soil temperatures but were related to transpiration rates. Average root resistances (10⁶ bar sec cm^–1) were 10.6, 8.4, and 5.8, and minimum resistances were 1.7, 1.2. and 0.6 for Dupontia, Carex, and Eriophorum, respectively. Leaf water potentials between – 15 and –20 bars occurred throughout both seasons. Water potentials were low enough to induce stomatal closure in Arctophila, Dupontia, and Potentilla but not in the other species. The simulation model predicted leaf water potentials similar to those measured. The model predicted stomatal closure to a degree which would decrease net photosynthesis in Arctophila, Dupontia, and Potentilla.