Application of Point Sampling in Forest Inventory for Timber Assessment: A Case Study of Siamese Rosewood Plantation, Trat Province

Abstract

            Forest resource inventory estimation to assess timber in a forest using the point sampling method is more convenient than the plot sampling method because it does not measure the plot dimensions. However, proper selection of the size of an appropriate point sampling basal area factor (BAF) is essential. This study tested various BAF sizes to assess the timber at a Siamese Rosewood (Dalbergia cochinchinensis Pierre.) plantation in the Tha Kum Noboru Umeda plantation, Trat province. Four BAFs of size 1, 2, 3, and 4 were established using a wedge prism in the plantation within a total area 450.98 rai. This plantation was divided into three age classes of 38, 41, and 42 years (representing different tree sizes and stand densities), with an area of 102.41 rai, 198.10 rai, and 150.47 rai, respectively. In total, 42 sampling points were inventoried. The data were analysed by comparing the timber basal area per hectare from the point sampling inventory using the various BAF sizes with the timber basal area based on census.

            The results showed insignificant differences in average basal area per hectare among the various BAFs. The results also showed that the BAF of size 1 was appropriate for the inventory of plantations with an average diameter at breast height (DBH) between 25.32 - 29.32 cm and a stand density between 130 - 137 trees per hectare. The BAFs 2, 3, and 4 were found to be appropriate for plantations with an average DBH between 26.41 - 30.09 cm and a stand density between 129 - 133 trees per hectare. The results can be used as a guideline for decision-making during the selection for an appropriate BAF size to assess the timber in other plantations with a similar average DBH and tree density.