PHREATOPHYTES UNDER STRESS: REVIEW OF STUDIES ON TRANSPIRATION AND STOMATAL CONDUCTANCE OF TAMARIX ACROSS A WESTERN US FLOODPLAIN
Transpiration (EL) and stomatal conductance (GS) were measured with stem heat-balance and Granier sap flux sensors on the dominant phreatophyte, saltcedar (Tamarix spp.), growing at six sites on a floodplain on the Lower Colorado River, US. Plant-specific leaf area index (LAPS) of shrubs was measured by leaf harvesting and Licor 2000 Plant Canopy Analyzer, and fractional cover (fc) was estimated by aerial imagery. Ground-area transpiration (EG) was calculated as EL × LAPS × fc. The sites presented environmental gradients with respect to distance from the river (0.2-1.5 km), depth to groundwater (2.4-3.5 m), groundwater salinity [1.9-24.0 g L-1 Total Dissolved Solids (TDS)] and soil texture (ranging from sand to clayey silts). EL varied from 1-3 mm m-1 leaf d-1 across sites, while LAPS ranged more narrowly, from 2-4, and fc varied from 0.5-0.95. Due to differences in EL, LAPS and fc, EG ranged from 1.2-9.5 mm d-1, nearly a 10-fold range. Only one site had EG characteristic of unstressed condition. We concluded that saltcedar is capable of high EG rates, but is also a stress adapted species, with EG highly variable over non-flooding riparian zones typical of regulated rivers. Salinity of the aquifer and vadose zone were identified as key constraints on saltcedar EG. Mean EG over the floodplain was only 40% of potential ET, contrary to earlier assumptions that saltcedar is invariably a high-water use plant.
Nagler, P.L., Glenn, E.P., Morino, K. and Hultine, K.R. (2013). PHREATOPHYTES UNDER STRESS: REVIEW OF STUDIES ON TRANSPIRATION AND STOMATAL CONDUCTANCE OF TAMARIX ACROSS A WESTERN US FLOODPLAIN. Acta Hortic. 991, 61-66
evapotranspiration, tamarisk, riparian ecology, water salvage sap flux measurements