Estimation of Timber Volume in Eucalyptus Plantations Using Satellite Images

Abstract

Accurate estimation of timber volume in commercial plantation can serve the industry as well as the environment than sustains them. A robust estimation methodology will help the plantation industry to efficiently manage this costly and long term investment to get the utmost return. Here, we investigated an approach to estimate timber volume in several Eucalyptus globulus plantation plots of varying ages in Chile.
Empirical relationships between temporal satellite imageries (Landsat ETM+) derived spectral feature and timber volume were investigated. A total of 12 Landsat ETM+scenes, both radiometrically and geometrically corrected, were selected to match with the dates of ground truth allometry data. Landsat ETM+has a ground resolution of 30 meters with a swath width of 185 km and visits the same position of the earth every 16 days making it suitable for monitoring plantations throughout a longer period of time with reasonable costs. Allometry data from a total of 8 plots spanning over four years (1999∼2004) were used. The area of the plots ranged from 30 to 150 ha and trees were planted between year 1992 and year 2000. Allometry data included diameter at breast height (DBH) , height of tree (H) of individual trees at selected subplots (0.02 ha) within each plot, collected by plantation management staff.
Mid-IR band 5 of ETM+followed by the green band of ETM+has the strongest correlation with timber volume for our study area. Out of several vegetation indices, Specific Leaf Area Vegetation Index (SLAVI) , which uses mid-IR band 5, showed strongest linear relationship with volume. The best relationship was used to estimate total volume in each plantation plot and to produce spatial volume map. Comparison between total estimated volume and actual observed volume at each plot showed the estimation accuracy was considered satisfactory. Spatial maps could be of importance for efficient forest management.