Deuterium tracing for the estimation of transpiration from trees Part 2. Estimation of transpiration rates and transpiration parameters using a time-averaged deuterium tracing method

A method for estimating transpiration rates and transpiration parameters, including the surface resistance term in the Penman-Monteith evaporation equation, from deuterium tracing experiments, where the samples were chemically time-averaged, is described. With this method only one deuterium tracer concentration analysis is required per tree compared with 90 using an earlier method. The calculation of surface resistance through solution of the convolution integral of the transpiration rate and the tracer concentration-time curve is described and the sensitivity of the surface resistance estimate to the flow parameters is investigated using as an example observations made on a 3-year-old plantation of Eucalyptus tereticornis growing in Karnataka, Southern India.