Electrical Resistance Tomograph (ERT): An innovative technique in estimation of heartwood content in standing trees of Swietenia macrophylla King

T3.30 Research advances towards sustainability for the high-value Meliaceae
Prajwal Mahalgod Bhadrappa1 , Baragur Neelappa Divakara1, Prashanth M1
1 Institute of Wood Science and Technology, 18th Cross, Malleshwaram, Bengaluru – 560 003 (Karnataka), India.

Abstract
Swietenia macrophylla King, also known as big-leaf mahogany, is a large deciduous tropical tree species native to Central and South America. S. macrophylla frequently reaching heights of over 20-30 m and diameter at breast height (DBH) of more than 1-1.5 m with an umbrella-shaped crown. S. macrophylla have been reported to grow in large plantations and also widely used for avenue planting in South India. Tree is gaining importance as a promising tree species for industrial plantations as well as for reforestation and afforestation. The ability to predict the growth and yield potential of S. macrophylla plantations is of considerable importance for planning plantation programmes. However, relatively very little reliable periodic stand measurement data are available. Added to this, information on heartwood development and estimation is totally lacking. Keeping this in view, tree tronic tomograms like Electrical Resistance Tomograph (ERT) was applied as a non-destructive method for advanced aiding for tree inspection to understand heartwood development and estimate in standing trees to predict the yield. In this study, we tested the validity of electrical resistance tomograph (ERT) to estimate heartwood diameter in big leaf mahogany by collecting core samples from fifty trees. The study revealed that the resistivity pattern in mahogany trees consisting of high resistivity in the inner part of the stem with lower resistivities on the outside. On an average resistance pattern of mahogany trees varies from 200 ohms to 943 ohms. The demarcation of SW-HW boundary was based on the distinct colour differentiation from blue (low resistance) to red (high resistance). A comparison between ERT and actual heartwood diameter shows a slope of the linear regression close to unity (0.90) with a narrow spread of values (R2 = 0.90). Finally, by this study Electrical Resistance Tomography proved to be a significant predictor of heartwood diameter in standing trees of mahogany trees.

Keywords: Mahogany, Electrical Resistivity Tomography, Heartwood, Resistance pattern, Core sample