The relationship between evapotranspiration by Phragmites communis Trin. and water table fluctuations in the Delta Marsh, Manitoba

Abstract

Evapotranspiration by Phragmites communis Trin. var. berlandieri (Fourn.) Fern. in the Delta Marsh of Manitoba, Canada was measured with small hydraulic load cell lysimeters [after Hanks and Shawcroft, 1965]. The measurements were recorded in two stands, available moisture being greater at Site A than Site B. Site A had a lower leaf area index than Site B. The major portion of the data was collected in the summers of 1970 and 1971. An evaporation lysimeter, operating in conjunction with the others, enabled a separation of evapotranspiration into its evaporation and transpiration components. Lysimeter transpiration was transposed to stand transpiration according to the ratio of leaf area of the lysimeters to leaf area index of the stand... The relationship between selected meteorological parameters and evapotranspiration was determined by simple and multiple linear regression analysis. Simple correlations between evapotranspiration and incoming short-wave radiation, net radiation, and relative humidity were all significant (p < 0.01). The simple correlations between evapotranspiration and wind were not significant while those between evapotranspiration and temperature were only significant in 1970. Multiple correlation coefficients, r = 0.80 to 0.90 were significant at p < 0.01. Regression coefficients for the temperature and wind terms in the equations were not significant but those on short-wave radiation, net radiation and relative humidity were highly significant (p < 0.01). Better correlations were obtained when net radiation replaced short-wave radiation in the analyses.