A rapid technique for recording and measuring the leaf area of conifer needle samples

An optical planimetric technique for measuring projected leaf area of conifer needle samples was developed that combines a rapid field recording method with an inexpensive hand-held optical scanner. The field recording method utilizes strips of diazo paper (blueprint paper), 10 x 28 cm, to make positive images of the needle samples. An analysis program calculates leaf area from the output files produced by the hand-held scanner. The results from this system were compared with results from a Li-Cor 3100 leaf area meter and from a digital camera-based image analysis system using both standard samples of known area and needle samples from three conifer species. All three systems produced similar results in terms of means and variances. The digital camera system typically had the lowest variances between successive measurements of the same sample. Most differences among the systems were not statistically significant. The system presented in this paper is inexpensive, easy to use, and provides a rapid and permanent method for recording and measuring the leaf area of conifer samples.