Transpiration rate of Prunus avium L seedlings inside an unventilated tree shelter

Transpiration rate was measured on one-year-old sheltered and control non sheltered Prunus avium L. seedlings using the stem heat balance method. The sheltered trees, protected by unventilated 2.1-m-tall plastic tubes, had an average transpiration rate 6 times less than control trees, although the leaves had a high conductance throughout the day. Lower transpiration rates in shelters may be explained by low values of net radiation, extremely small water vapour deficit, and low windspeed resulting in a high boundary layer resistance to water transfer. Consequences of such low transpiration are discussed, and recommendations regarding the optimal use of treeshelters are deduced. The removal or sudden ventilation of a treeshelter during the growing season should be avoided, and weeding the sheltered trees is essential. (C) 1997 Elsevier Science B.V.