EFFECTS OF HEAT-BALANCE STEM-FLOW GAUGES AND ASSOCIATED SILICONE COMPOUND ON ASH TREES

Stem-flow gauges were used to estimate water use by young ash trees (F raxinus excelsior L.) growing in the field at the University of Nottin gham, Sutton Bonington Campus, Loughborough. In 1992 and 1993 the tree s were exposed to episodes of elevated ozone concentration or to clean air in open-top chambers. Trunk constriction was observed on trees fi tted with gauges in 1992, resulting in impaired flushing and growth in the spring of 1993. Despite precautions, constriction was again obser ved in 1993. Also in 1993 an experiment was conducted to assess the ef fect on ash trees of the silicone compound used with gauges to enhance performance and aid fitting to the trunks. Trunk constriction was obs erved when the compound was applied to the trunks without the use of g auges or any other physical restriction to radial growth. Data which d emonstrate the degree of constriction are presented.