Myung Bo Lee

Estimating the spatial pattern of human-caused forest fires using a generalized linear mixed model with spatial autocorrelation in South Korea

Most forest fires in Korea are spatially concentrated in certain areas and are highly related to human activities. These site-specific characteristics of forest fires are analyzed by spatial regression analysis using the R-module generalized linear mixed model (GLMM), which can consider spatial autocorrelation. We examined the quantitative effect of topology, human accessibility, and forest cover without and with spatial autocorrelation. Under the assumption that slope, elevation, aspect, population density, distance from road, and forest cover are related to forest fire occurrence, the explanatory variables of each of these factors were prepared using a Geographic Information System-based process. First, we tried to test the influence of fixed effects on the occurrence of forest fires using a generalized linear model (GLM) with Poisson distribution. In addition, the overdispersion of the response data was also detected, and variogram analysis was performed using the standardized residuals of GLM. Second, GLMM was applied to consider the obvious residual autocorrelation structure. The fitted models were validated and compared using the multiple correlation and root mean square error (RMSE). Results showed that slope, elevation, aspect index, population density, and distance from road were significant factors capable of explaining the forest fire occurrence. Positive spatial autocorrelation was estimated up to a distance of 32 km. The kriging predictions based on GLMM were smoother than those of the GLM. Finally, a forest fire occurrence map was prepared using the results from both models. The fire risk decreases with increasing distance to areas with high population densities, and increasing elevation showed a suppressing effect on fire occurrence. Both variables are in accordance with the significance tests.

Fine structure and X-ray microanalysis of silicified woods from a Tertiary basin Pohang, Korea by scanning electron microscopy.

Anatomical descriptions are provided on silicified woods from a Tertiary basin Pohang, Korea by scanning electron microscopy and X-ray microanalysis. The silicified woods appeared to retain the original exterior morphology of the once grown trees, and exhibited various colors on the surface. As a component of the axial system in the secondary xylem, pores were oval to globose and measured approximately 200-300 microm in diameter in transverse planes. Seemingly bordered pits were also frequently observed in the tracheary elements. As a component of the axial system in the secondary phloem, sieve elements were found to have many sieve pores that were filled with numerous fine particles. In tangential planes, rays in the vascular cambium were approximately 500 microm long, and usually several cells wide (multiseriate). Meanwhile, several forms of microbial growth such as bacterial chains and hyphal growth of either fungi or actinomycetes were evident in the vessel lumens of unpolished silicified wood pieces. Some fracture surfaces were mainly characterized by the occurrence of polyhedral crystals, probably quartz, in the fissures. By X-ray microanalysis, iron was detected from the brown-colored regions, whereas calcium was also detected together with iron in the black-colored regions. Based on the rare occurrence of tracheids as the axial system in the secondary xylem, the silicified woods in this study can be intrinsically categorized into angiosperm groups in the region.

Crown fuel characteristics and carbon emission from Japanese red pine stands burned by crown fire in Mt. Palgong, South Korea

Carbon emissions from forest fires are considered an important factor of ecosystem carbon balance and global climate change. Carbon emissions from Japanese red pine stands (Pinus densiflora S. et Z.) burned by crown fire were estimated at Mt. Palgong in Daegu Metropolitan City, and crown fuel characteristics, including crown bulk density, crown base height, and fuel moisture content of Japanese red pine, were analyzed. Total biomass combusted was calculated by subtracting the biomass of burned stands from that of unburned stands exhibiting similar stand structures and site environments. Ten trees in the unburned area and five trees in the burned area were cut by using direct harvesting techniques to estimate crown layer biomass. All biomass sampled was oven-dried and weighed. The dry weight ratios of stems, branches, and needles were 70%, 21%, and 9%, respectively. The available fuel load susceptible to combustion during the crown fire spread was equivalent to 55% of the crown layer biomass. The crown bulk density was 0.24 kg/m3 on average. The estimated amount of CO2 was 23,454 kg CO2/ha for the crown layer. These results will be useful for calculating the amount of CO2 emitted from forest fires and for developing a forest carbon model in P. densiflora forests.

Estimation of non-CO2 GHGs emissions by analyzing burn severity in the Samcheok fire, South Korea

This study was performed to estimate the emission of non-CO2 greenhouse gases (GHGs) from biomass burning at a large fire area. The extended methodology adopted the IPCC Guidelines (2003) equation for use on data from the Samcheok forest fire gathered using 30 m resolution Landsat TM satellite imagery, digital forest type maps, and growing stock information per hectare by forest type in 1999. Normalized burn ratio (NBR) technique was employed to analyze the area and severity of the Samcheok forest fire that occurred in 2000. The differences between NBR from pre- and post-fire datasets are examined to determine the extent and degree of change detected from burning. The results of burn severity analysis by dNBR of the Samcheok forest fire area revealed that a total of 16,200 ha of forest were burned. The proportion of the area characterized by a ‘Low’ burn severity (dNBR below 152) was 35%, with ‘Moderate’ (dNBR 153–190) and ‘High’ (dNBR 191–255) areas were at 33% and 32%, respectively. The combustion efficiency for burn severity was calculated as 0.43 for crown fire where burn severity was ‘High’, as 0.40 for ‘Moderate’ severity, and 0.15 for ‘Low’ severity surface fire. The emission factors for estimating non-CO2 GHGs were separately applied to CO 130, CH4 9, NOx 0.7 and N2O 0.11. Non-CO2 GHGs emissions from biomass burning in the Samcheok forest fire area were estimated to be CO 44.100, CH4 3.053, NOx 0.238 and N2O 0.038 Gg.

Developing a site index model considering soil characteristics for Pinus thunbergii stands grown on the west coast of Korea

Height model of the dominant tree was developed and derived site index curves of Pinus thunbergii, which is the main species of windbreak forests along the west coast of Korea. The site index of a tree is affected by various environmental factors. In the present study, however, the soil characteristics of P. thunbergii stands, which are scattered along the west coast of Korea were used. Eight sites of windbreak forest were investigated from October 2011 to October 2012. The Schumacher polymorphic equation was the most suitable equation to develop a site index model of P. thunbergii stands, and it was the best site index model when Ca-P and fungus were applied to the asymptotic parameter (α). The equation yielded site index curves using the developed model, which is based on trees aged 50 years, considering the soil characteristic factors of P. thunbergii stands in different areas. The site index model and site index curves suggest important growth information, such as windbreak forests, green spaces development, and height growth estimation, which are needed for management of the stands, with consideration of the proposed soil characteristic factors of this study.