Earticle

This study examined the relationship between the number of forest fires and days with no rainfall based on the national forest fire statistics data of the Korea Forest Service and meteorological data from the Open MET Data Portal of the Korea Meteorological Administration (KMA; data.kma.go.kr) for the last 30 years (1991-2021). As for the trend in precipitation amount and non-rainfall days, the rainfall and the days with rainfall decreased in 2010 compared to those in 1990s. In terms of the number of forest fires that occurred in February–May accounted for 75% of the total number of forest fires, followed by 29% in April and 25% in March. In 2000s, the total number of forest fires was 5,226, indicating the highest forest fire activity. To analyze the relationship between regional distribution of non-rainfall periods (days) and number of forest fires, the non-rainfall period was categorized into five groups (0 days, 1-10 days, 11-20 days, 21-30 days, and 31 days or longer). During the spring fire danger season, the number of forest fires was the largest when the non-rainfall period was 11-20 days; during the autumn fire precaution period, the number of forest fires was the largest when the non-rainfall period was 1-10 days, 11-20 days, and 21-30 days, showing differences in the duration of forest fire occurrence by region. The 30-year trend indicated that large forest fires occurred only between February and May, and in terms of the relationship with the non-rainfall period groups, large fires occurred when the non-rainfall period was 1-10 days. This signifies that in spring season, the dry period continued throughout the country, indicating that even a short duration of consecutive non-rainfall days poses a high risk of large forest fires.

Q. mongolica and Q. dentata are representative species of deciduous forest communities in Korea and are known to be relatively resistant to soil drying condition among Korean oaks. This study attempted to elucidate the degree of competition and ecological niche characteristics of the two species by comparing the ecological responses of the two species according to soil moisture. Competition between Q. mongolica and Q. dentata was shown to be more intense under the conditions where moisture content was low than under the conditions where moisture content was high. As for the ecological niche overlaps of the two species for soil moisture, the structural traits of plant such as stem diameter overlapped the most, the traits of biomass such as petiole weight overlapped the least, and photosynthetic organ-related traits such as leaf width and length overlapped intermediately. When looking at the competition for soil moisture between the two species, it can be seen that Q. mongolica won in nine traits (leaf width length, leaf lamina length, leaf lamina weight, leaf petiole weight, leaf area, leaves weight, shoot weight, root weight, and plant weight) and Q. dentata won in the remaining seven traits (leaf petiole length, leaves number, stem length, stem diameter, stem weight, shoot length, and root length). Competition between the two species for the moisture environment of the soil was shown to be intense under the conditions where moisture content was low. The degree of competition between Q. dentata and Q. mongolica for soil moisture is high under the conditions where soil moisture content is low, and it is judged that Q. mongolica is more competitive for soil moisture than Q. dentata.

Forestry crane work in a forest harvester or forwarder is regarded as one of most hard work requiring a very high level of operation skill. The operator must handle two or more multi-axes joysticks simultaneously to control the multiple manipulators for maneuvering the crane-tip to its intended location. This study has been carried out to develop a crane-tip controller which can intuitively maneuver the crane-tip, resulting in improving the productivity by decreasing the technical difficulty of control as well as reducing the workload. The crane-tip controller consists of a single 2-axis joystick and a control algorithm run on microcontroller. Lab-scale forestry crane was constructed using electric cylinders. The crane-tip control algorithm has the crane-tip follow the waypoints generated on the given path considering the dead band region using LBO (Lateral Boundary Offset). A speed control gain to change the speed of relevant cylinders relatively is applied as well. By the P (Proportional) control within the control interval of 20 msec, the average error of crane-tip control on the predefined straight path turned out to be 14.5 mm in all directions. When the joystick is used the waypoints are generated in real time by the direction signal from the joystick. In this case, the average error of path control was 12.4 mm for straight up, straight forward and straight down movements successively at a certain constant speed setting. In the slant movement of crane-tip by controlling two axes of joystick simultaneously, the movement of crane-tip was controlled in the average error of 15.9 mm when the crane-tip is moved up and down while moving toward forward direction. It concluded that the crane-tip control was possible using the control algorithm developed in this study.

The study was conducted to establish a method for the proliferation of hybrid poplar (P. alba × P. glandulosa) clone Bongwha1, an excellent biomass species. It was found that to collect the cuttings of Bonghwa1, it was necessary to use the main stem rather than the axillary branch. Stem growth by green-wood cuttings showed a tendency to decrease as the length of the collected cuttings increased, but the survival rate was low. Therefore, modified leafy stem cutting was attempted to increase the survival rate of the cuttings. In the modified leafy stem cutting method, 4 leaves were included in the cuttings, and especially, cuttings were performed using cuttings containing 2-4 cm xylem parts. Leafy stem cutting increased root growth and the number of stems, as well as the survival rate of hybrid poplar clone Bongwha1 compared to green-wood cuttings. The root growth of the leafy stem cutting poplar was better as there was more xylem part. Using two-year-old nursery stocks, the leafy stem cutting was used to produce about 66 cuttings. This study is expected to contribute to the mass propagation of high-quality nursery stocks.

The timing of seed harvesting is an important decision in the management of seed orchards because it affects seed quality and yield. To investigate the effect of cone harvest time on seed quality and determine the optimal harvesting time, cones were regularly collected in seven times and germination tests were performed at each harvest time in two clonal seed orchards of Chamaecyparis obtusa. As cones developed, the percentage of seed germination increased before cone moisture content began to decrease significantly. The moisture contents of cones were highest at the first collection as 68.3% and 67.3% in Jeju and Gochang seed orchards respectively. At this time, germination speed was slowest, indicating poor seed vigour. The highest germination was found at the second stage in Jeju (36.5%) and at the seventh stage in Gochang (28.6%) seed orchard. The germination speed increased as cone moisture content decreased. Additionally, changes of seed vigour differed among the developmental stages in both seed orchards. Consequently, the optimal cone harvest time of C. obtusa seed orchards in Jeju was early September when high germination percentage was obtained. In Gochang seed orchards, late October was optimal cone harvest time when the germination speed was fast and the cone moisture content decreased.

Quarrying of rock for construction purposes is a significant industry in any economy but has its negative impact. This study examined the impact of quarry activities on surrounding vegetation in Ogun State. Geographic Information System approach was used to map the various quarry locations present in different Local Government Areas in Ogun State; of which eight sites were selected namely Isara, Idode, Iwaye, Ogbere, Ilagbe, Adelokun Baaki Ake and Igodo. Vegetation composition analyses were carried out on the eight sites using Haga Ultimeter and chlorophyll content analysis. Data were subjected to descriptive and inferential statistics using SAS package (9.4 version). Sixty quarries were identified with Odeda Local Government Area (38.3%) having the highest percentage of quarry. The vegetative compositions analyses showed that Albizia zygia had the highest frequency (7) among identified plants in the quarries. The chlorophyll content of Albizia zygia in the wet season (492.2 mg Chl/m2) was significantly higher than dry season (464.4 mg Chl/m2) in all locations. However, Baaki Ake (Albizia zygia) chlorophyll content was highest among other locations in both seasons. In conclusion Albizia zygia showed highest resistance to quarry activities, hence common among other plants identified around the quarries.

A study was designed to investigate the pattern of sexual dimorphism in a plantation of Garcinia kola . Twenty trees were randomly selected for the study and have been observed to flower regularly. A total of 100 inflorescence were randomly collected from the crown of each tree and 500 flowers randomly assessed within the period of four (4) flowering seasons. Floral sex assessment was done visually and with a hand magnifying lens; floral morphometric measurements (i.e. pedicel and perianth length and breadth), inflorescence length, and breadth) was taken using a veneer caliper; number of flowers per inflorescence and inflorescence per twig was counted; while, data analysis was conducted on excel using analysis of variance and pairwise t-test comparison. Four floral sexes were identified in the G. kola plantation studied which were unisexual male flowers, unisexual female flowers, cosexual unisexual male flowers, and cosexual hermaphrodite flowers. Three tree sexes were identified viz: inconstant male, invariant female, and cosexual trees. The plantation was significantly sexually dimorphic in floral sex and phenotypic traits (i.e. pedicel and perianth size), and as well as sexually dimorphic in tree sex and reproductive phenotypic traits (i.e. inflorescence size, number of inflorescences per twig, and number of flower bud per inflorescence). The sexual system of the plantation was therefore trioecious with features suggestive of evolving dioecy through the gynodioecious pathway.

This study was conducted to determine the seed dormancy types of Sambucus racemosa subsp. pendula Nakai and S. williamsii Hance. Low temperature stratification (1, 2, 3, 4 months) and GA3 treatment (1,000 mg/L) were performed on seeds to determine the type of seed dormancy. After the treatment, seeds were placed on a petri dish at 25°C under light conditions. The germination rate and mean germination time were investigated. Results showed that cold stratification was effective in breaking the dormant state of the seed in both species. In the low temperature stratification treatment, the seed germination performance was improved as the treatment period was prolonged. Gibberellin treatment was effective in breaking the dormant state of S. racemosa subsp. pendula without low temperature stratification. However, S. williamsii did not break the dormant state of the seed by gibberellin treatment without low temperature stratification treatment. In the gibberellin treatment, germination performance was improved according to the low temperature stratification treatment period. As a result of this study, the seeds of S. williamsii have both an intermediate complex and a deep complex morphophysiological dormancy (MPD). In comparison, it was found that the S. racemosa subsp. pendula had intermediate composite MPD.

Increasing life expectancy leads to a rise in the prevalence of aging-related mental diseases and a concomitant increase in the financial and societal pressures related to their prevention and management. This issue is attracting increasing attention from researchers. Therefore, this study aimed to determine whether a healing program in a forest environment is effective for improving cognitive function, depression, anxiety, and stress in elderly people. A nonequivalent control group pretest-posttest design was used. The experimental group consisted of 18 males and females aged 60 to 80 years who participated in a forest healing program for seven days, while the comparison group comprised 10 people with similar demographics. For the process of data analysis, this study performed a cross-analysis to determine the homogeneity of the data and carried out the Wilcoxon signed-rank test, a nonparametric statistical test, to verify the significance of each group. Participation in the forest healing program led to a significant improve-ment in cognitive function (p=0.030). The levels of depression decreased, but this result was not statistically significant. The levels of anxiety decreased significantly (p=0.004). The mean cortisol score, a measurement of stress, decreased, but it was not statistically significant. These findings confirmed the effectiveness of this program for improving certain mental conditions of elderly people, and affirmed that the use of long-term forest healing programs can be expected to alleviate national pressures created by aging societies.