A Hydrostatic Lysimeter to Measure Evapotranspiration Under Remote Field Conditions

A small hydrostatic lysimeter for use in shallow tundra soils was constructed based on the design of Hanks and Shawcroft (1965). A percolation vessel situated below the lysimeter drained the lysimeter of excess water induced by heavy rainfall and gave a measure of the amount retained by the soil and that lost from the soil.Soil temperature and moisture measured within the lysimeter and in the adjacent soil indicate that natural conditions were closely duplicated in the lysimeter in spite of its small size.Measurement of wind velocity in the vicinity of the lysimeter indicated that the unvegetated boundary at the edge of the lysimeter has more effect in a sedge community of Carex bigelowii than in a cushion plant community of Diapensia lapponica.The use of a sealed “dummy” lysimeter in conjunction with lysimeters containing live plant systems permitted correction of all environmental variables, the major one being temperature.A suggestion was made for the way in which the transpiration data might be analyzed, and expressed on a gram per square decimeter of leaf area per hour basis.The lysimeter was constructed from inexpensive and easily obtainable materials. It had an accuracy equal to 0.25 mm of water and was found to be a simple and accurate way of measuring evapotranspiration in an alpine tundra environment.