Evaporative demand across a range of microsites in partial-cut boreal forests

Relative rates of evaporative demand were measured across a range of microsites in partial-cut boreal mixed-wood forests in northern Alberta using atmometers (evaporimeters); evaporation was measured by water loss from porous ceramic cones. The atmometers provided a consistent index of evaporative demand, i.e. a measure of water loss from a moist surface, when compared to potential evapotranspiration calculated from meteorological data collected at the study sites. The average evaporative demand at 2 m height was similar in two different patterns of partial harvest, but these were intermediate between that of nearby uncut forests and clear-cut harvests. There were differences in evaporative demand between 5 m wide extraction trails and adjacent partial-harvested areas. Rates of evaporative demand were related to small-scale spatial differences in basal area of the residual trees. This study demonstrates that these inexpensive instruments are suitable for replicated measurements of relative evaporative demand across a variety of forest habitats.