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Abstract. Rinnamang S, Sirirueang K, Supavetch S, Meunpong P. 2020. Estimation of aboveground biomass using aerial photogrammetry from unmanned aerial vehicles in teak (Tectona grandis) plantation in Thailand. Biodiversitas 21: 2369-2376. Thailand is one of the best teak planting locations in the world. Teak is one of the most species planting and a significant source of high-value timber in Thailand. For plantation management, biomass is one of the important factors while determining the production of a plantation and also for sustainable forest management. Unmanned Aerial Vehicles (UAV) have the ability to produce 3D RGB digital images which can be used to study the plantation characteristics. This study aimed to use aerial images and photogrammetry techniques derived from unmanned aerial vehicles (UAV) to estimate teak biomass in Thong Pha Phum plantation, Kanchanaburi Province, Thailand. We conducted our study on 15-and 36-year-old teak stands, and compared the tree dimension between data obtained from field measurement and that from aerial images and photogrammetry techniques. In the 15-year-old stand, the average tree height estimated from the UAV and ground-truthing were 12.34 and 13.06 m, respectively. In the 36-year-old stand, the average tree height from the UAV and ground-truthing were 28.87 and 29.39 m, respectively. We found that in both stands, the difference between data generated from the UAV and ground-truthing data was not significant (p-value = 0.07 and 0.306, respectively). There was also a strong correspondence between tree height estimated from the UAV and that measured on the ground which is indicated by the high R2 (i.e. 0.70 and 0.64 for the 15-and 36-year-old stands, respectively). Using UAV generated data, the total biomass of 15-and 36-year-old stands was estimated to be around 42.07 t ha-1 and 67.13 t ha-1, respectively. The overall results suggest that UAV can be used as an effective tool to survey and monitor stand’s productivity in teak plantation.

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Abstract. Meunpong P, Penboon C, Kuasakun N, Wachrinrat C. 2021. Tree dimension and environmental correlates of heartwood content in Siamese rosewood (Dalbergia cochinchinensis). Biodiversitas 22: 3297-3303. Siamese rosewood (Dalbergia cochinchinensis) is considered amongst the prime timber varieties in high demand with the wood fetching high prices in the international timber market. Therefore, illegal logging and smuggling of Siamese rosewood from natural forests poses a severe problem in Thailand. Heartwood and its content is the most valuable part of Siamese rosewood, which in practice, cannot be measured directly in living trees. Hence, we investigated the relationship between the heartwood content of Siamese rosewood, and tree dimension and environmental characteristics across eleven plantations throughout Thailand construct a model for predicting the heartwood content using specific environmental variables. The results indicate that there were differences in the mean annual increment of all measurement parameters (d0, d30, dbh, and total height of a tree) across eleven plantations studied. However, we did not find any statistically significant differences between the increments in heartwood diameter. Furthermore, we found that suitable location for Siamese rosewood plantation could result in doubling of growth rate. We report that dbh was the most relevant variable and could be used as a predictor for heartwood content. In terms of environmental variables, soil properties at top layer that affect the heartwood content were particle density, organic matter, and silt particles. Using the resulted equation formulated in this study may be useful when planning areas for suitable plantations of Siamese rosewood in Thailand.

Teak is an important and valuable tropical hardwood species. In this study, we developed and evaluated suitable taper equations for teak growing in Western Thailand using a formulation of Goodwin cubic polynomial model combined with a bark thickness model. The best taper model calibration was selected based on goodness-of-fit and leave-one-out cross validation statistical testing. In total, 12 different model calibrations were tested, with Thong Pha Phum (TPP) 2 being the most suitable for teak in Western Thailand. The mean prediction error of three validation statistics: (prediction of diameter under bark given height; prediction of height given diameter under bark; and prediction of under bark volume given log length) were within 10% and the overall validation index was 5.454, which was the lowest when compared to other calibrations. A comparison of TPP 2 with a teak taper equation developed for Northern Thailand, using a graphical analysis of the stem shape and bark thickness, indicated that the teak trees growing in the two regions have similar stem shapes, but the trees in Western Thailand tend to have a thicker bark. These results will also help in further work as they indicate that bark thickness equations are particularly important.