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- Growth and yield models for Eucalyptus species using geospatial...
Growth and yield models for Eucalyptus species using geospatial technology in Aek Nauli, North Sumatra Province, Indonesia.
Dissertation Abstract:
This study was conducted primarily to develop a yield prediction model for forest plantation of Eucalyptus spp. in Aek Nauli, North Sumatra, Indonesia as a contribution toward sustainable forestry development and management. Specifically, it aimed to develop growth and yield models for Eucalyptus plantations, test the models to identify the best growing species, integrate growth and yield models into a GIS model, and recommend appropriate management strategies to improve growth and yield.
The data in this study came from 650 rhombic plots consisting of 106 PSPs and 544 inventory plots. Six candidate non-linear regression equations using original ages and initial and projection ages were tested and assessed for statistical validity and accuracy in predicting yield.
Models using initial age, specifically Model 2 was found consistently to be the best model in almost all Eucalyptus plantations. Among the models using initial and projection age, Model 4 was the best model. Model 2, which use original ages, is better than Model 4, which use initial and projection age because the former is more reliable and its growth curve follows a sigmoid shape. There is significant difference between models among Eucalyptus species to predict the merchantable volume. Consequently, each Eucalyptus species has a specific model to predict the yield.
Results showed that E. hybrid had the highest (230 m<sup>3</sup>/ha) of average predicted volume in year 7 and E. pellita had the lowest (104 m<sup>3</sup>/ha). The most important factor affecting yield of E. urophylla and all species was rainfall. For E. grandis, E. pellita, and mixed Eucalyptus, the important factors were stand density, elevation, interaction site index, and age.
Environmental requirements for viable plantations of various Eucalyptus species are site index (15–25 m), stand density (800–1,200 tree/ha), spacing (6–9 m<sup>2</sup>), plot size (0.025–0.04 ha), depth of top soil (20–40 cm), rainfall (100–400 mm/month),slope (0–45%), elevation (600–1,700 masl), and groups of soil (A, C, and E).