**1. Introduction**

Resin is one of the traditional non-timber forest products (NTFPs) which represents all kinds of non-timber resources produced in forests [1] in the Republic of Korea as in other countries. The use of NTFPs has remained in the form of knowledge delivered from generation to generation in a local community, rendering the community as a fundamental data source of the NTFPs. In the records of traditional forest knowledge (www.koreantk.com), resin is defined as a raw material used in traditional crafts, medicine, foods, life technology, and agriculture [2]. Various uses of pine resin with honey mel can be found in the old literature "*CHISENGYORAM*" (literally means the guideline for management of livelihood, 1691) [3], "*GOSASINSEO*" (literally means the new book for deep thinking, 1771) [4], and "*NONJEONGHOIYO*" (literally means the technical book for agriculture and forestry, 1831) [5] in Korea.

Korea was under Japanese rule between 1910 and 1945, and thus, Korea was greatly influenced by Japan's socioeconomic policy during this period. Japan entered war in the late 1930s and implemented the first seven-year plan to produce synthetic oil in 1937 [6]. The seven-year plan was implemented by the Japanese government because sufficient synthetic oil was not produced by the domestic companies

to support fuel for weapons [7]. To obtain resin from red pines (*Pinus densiflora*), the panel hacksaw method, in which a cut of around 150 cm length was made, was applied. On the other hand, in the traditional method in the Republic of Korea, the so-called chisel method was used, whereby a cut was made of approx. 6 cm width and 12–21 cm length [2].

The tree-ring analysis technique, also known as dendrochronology, is a powerful tool to date annual rings in woody plants. In the dating technique, the ring-width time series patterns obtained from the same tree species under similar growing conditions are synchronized with each other. This is called cross-dating in dendrochronology [8,9]. Cross-dating has been broadly applied to date annual rings in forest trees to investigate their dead and/or wounded years [10,11] as well as use their wood in archaeological architecture [12], wood craft [13], picture frames [14], musical instruments [15], and tracing wood trade [16]. The dating results of the cuts in tree rings could provide historical information on natural events, e.g., forest fire [17,18], landslide [19], flash flood [20,21], insect damage [22], and human activities, e.g., resin or latex collections.

The primary aim of the present study was to date resin collection from red pines (*Pinus densiflora*), estimate the tree size in the years when the resin was collected, and verify the current conditions of the trees. The results would serve as a reference to understand the changes in resin collection methods by year and determine forest policy on the sustainable usage of forest resources by resin collection methods.
