A δ(2)H Isoscape of blackberry as an example application for determining the geographic origins of plant materials in New Zealand

In this investigation, two previously reported precipitation δ(2)H isoscapes for New Zealand were used to develop a δ(2)H isoscape for blackberry (Rubus sp.) leaf. These isoscapes were calibrated using the measured δ(2)H values of 120 authentic blackberry leaf samples collected from across the country. A regression model based on environmental variables available for New Zealand was also determined to predict δ(2)H values measured from blackberry leaves without initially modelling the precipitation δ(2)H values. The three models were compared for their accuracy and precision when assigning 10 samples of blackberry leaves for their geographic location based on their measured δ(2)H values. One of the models based on a precipitation isoscape was similar in accuracy and precision of assignment to the model determined from the environmental variables and provides an approach for determining valid isoscapes for future plant materials.