This study was conducted to develop a simple volume model for the Larix kaempferi species in the Central Region of South Korea. General volume model forms were used and validated using a subset of the data collected for the L. kaempferi species. A total of 550 trees were collected in the different L. kaempferi stands through destructive sampling. The dataset was randomly divided into two: 80% for initial model development(seven volume models) and 20% for model validation. The 100% dataset was used for the final model fitting. Evaluation statistics including bias(Ē), absolute mean deviation(AMD), root mean square error(RMSE), coefficient of determination(R2), and the Akaike Information Criterion values(AIC) and weight (AICw) were used to assess performance of the different volume models. Rank analysis was employed and the first five best volume models were chosen for the model validation and final model fitting. The evaluations showed that volume model 4(V=aDBHb*Hc) had the best performance, while volume model 3(V=aDBH+bDBH2), which has a single variable, had the poorest performance.

To develop an empirical degree-day model for predicting the spring flight period of the bark beetle, Ips subelongatus Motschulsky, based on field observation, field studies were biweekly conducted in three Japanese larch (Larix kaempferi) forests in In-je, Korea from 2013 to 2014. To validate this degree-day model, we compared the model-predicted values with observed emergence data of I. subelongatus in 2015 spring at one of the sites. The flight period of over-wintering generation began on April and ended May, and flight of next generation lasted until October. The lower developmental threshold temperature (LDT) was estimated using spring emergence of I. subelongatus and field temperatures. Then a degree-day model was constructed, based on LDTs estimated from field observations data. The baseline temperature with the highest coefficient of determination was considered the LDT, and this was estimated to be 6.0℃. The explanatory power of the model was 88%. This model accurately predicted the flight of I. subelongatus in 2015 spring, as the estimated median flight dates was 1 days earlier than the corresponding observed flight date. The results of the goodness-of-fit test did not differ between observed and estimated values (ks = 0.21, P = 0.54).

The effects of thinning on community diversity of wood-boring beetles were examined in Japanese Larch (Larix kaempferi) forest in In-je, South Korea in 2013. Three study sites were selected and thinning in the plots was conducted in 2010, spring 2012, and autumn 2012, respectively. Wood-boring beetles were collected every week using the 12-unit Lindgren multi-funnel traps with pheromone lure (Ipsdienol +50/-50 40mg, Ipsenol +50/-50 40mg) from mid-April to early November. Total 5 families (Cerambycidae, Curculionidae, Dryophthoridae, Scolytidae, Platypodidae), 62 species, and 26,638 individuals were collected. Diversity indices were 2.08, 2.02 and 0.76, and evenness indices were 0.55, 0.49 and 0.19 in 2010, spring 2012 and autumn 2012 thinning area, respectively. Among wood-boring beetles, the number of species of bark and ambrosia beetles were accounted for 44.4, 41.9 and 46.3% in 2010, spring 2012 and autumn 2012 thinning area, respectively. The number of individuals of bark and ambrosia beetles were accounted for 86.9, 82.2 and 98.4% in 2010, spring 2012 and autumn 2012 thinning area, respectively. Our results showed that the density of wood-boring beetles was the highest in the most recent thinning area, suggesting that thinning timing can influenced on the abundance of bark and ambrosia beetles. Among them, Ips subelongatus, I. acuminatus, and I. sexdentatus are species that mainly attack Japanese Larch. Ips subelongatus emerged faster than others and was the most dominant species.