Southwest Korea Research Articles

First Report of Leaf Spot on Eriobotrya japonica Caused by Alternaria alternata in Southwest Korea.

Loquat (Eriobotrya japonica) is a crop cultivated in Southwest Korea, covering an area of 101 ha and yielding 120 tons at harvest (KASS, 2024). Due to its high-income potential, the cultivation area is gradually expanding. In May 2023, 30% of leaf brown spots were observed on all three trees in the Suncheonman National Garden, Suncheon (3488'57.97" N, 12750'92.83" E). As the disease progressed, the brown spot gradually enlarged, turning greyish-ivory inside and forming concentric circles. Three leaf lesions from each tree were cut into 5 x 5 mm pieces, surface-sterilized with 70% ethanol for 1 min, and washed in sterile water three times to isolate the pathogen potentially responsible for these symptoms. The samples obtained were subsequently cultured on 1.5% water agar and then incubated in the dark at 25℃. A total of nine isolates were obtained, with three isolates from each of the three trees through single-spore isolation, namely SYP-1202-1 to 3, SYP-1202-4 to 6, and SYP-1202-7 to 9. The colonies reached 90 mm in diameter after 10 days on potato dextrose agar (PDA), initially dark green, and turned sooty gray after 2 weeks. The hyphae grown on a 0.6% KCl medium for 3 days produced long chains containing three to twelve conidia. The conidia were ellipsoidal or obpyriform in shape and light brown. The conidiophores were straight or curved, measuring 12.1-75.3 x 1.6-4.8 μm (n = 100). The primary and secondary conidia measured length × width of 19.1-60.6 × 6.1-14.4 μm and 8.4-27.8 × 3.5-9.5 μm (n = 100), respectively. The conidia had 1 to 7 transverse and 0 to 3 vertical septa. The morphology of the nine isolates was identical and consistent with Alternaria species (van der Waals et al., 2011; Woudenberg et al., 2015). For molecular identification, ITS (OR844500 to OR844508), GAPDH (OR866383 to OR866391), TEF1 (OR866392 to OR866400), RPB2 (OR866401 to OR866409), Alt a1 (OR866410 to OR866418), endoPG (OR866419 to OR866427), and OPA10-2 (OR866428 to OR866436) sequences from SYP-1202-1 to 9 showed a 100% (515 bp/515 bp), 100% (579/579), 100% (240/240), 100% (753/753), 95.1% (449/472), 100% (448/448), and 100% (634/634) identity with that of type strain A. alternata CBS 115152 (KP124348, KP124202, KP125124, KP124816, KP123896, KP124049, and KP124658, respectively). A pathogenicity test was conducted on three 5-year-old E. japonica cultivar Daebang trees in pots. The surface of the five leaves per tree was sterilized with 70% ethanol for 1 min. Before inoculation, the leaves were wounded with sterile needles and sprayed with the conidial suspension (1×106 conidia/ml) produced from a 1-week-old culture grown on PDA. In contrast, control leaves were sprayed with sterile distilled water. The inoculated leaves were wrapped with black plastic bags and kept at 100% relative humidity for two days. At seven days post-inoculation, symptoms were observed on the wounded leaves, whereas the nonwounded and control leaves did not exhibit any symptoms. The experiment was performed three times in the greenhouse. For each experiment, pathogens were reisolated from the two symptomatic leaves per plant. The identity of the reisolated pathogens was then confirmed via analysis of ITS and RPB2 genes, thereby confirming adherence to Koch's postulates. To the best of our knowledge, this is the first report of E. japonica being infected by A. alternata in Korea. This report provides important information to support effective disease control strategies for E. japonica in orchards in southern Korea.

Monitoring of Positive List System on Residual Pesticides Analysis of Agricultural Products in Southwest of Korea

Pesticide residues must be managed for food safety and regulations are being strengthened worldwide. In Korea, the Positive List System (PLS) was introduced to prevent the misuse and manage unregistered pesticides. The PLS is a system that applies 0.01 mg/kg to crops for which maximum residue limits is not set. A more stringent regulatory system could lead to an increase in agricultural products that exceed standards. Therefore it is necessary to confirm the change in the determination rate of agricultural products exceeding the previous pesticide residue standards. In terms of climate change, temperature increase and changes in precipitation patterns are the main pest and pathogen infection determinants. Complex interactions and climate variability will lead to more frequent spraying of pesticides and eventually affect consumer exposure at the end of the food chain. Therefore, we confirmed the relationship between temperature and precipitation, which are climate factors and pesticide residues. Agricultural products (n=5,560) distributed at wholesale market (SeoBu, GakHwa) in the southwest Korea were collected and 311 kind of residual pesticides were analyzed using GC-MS/MS and LC-MS/MS. This study could serve as basic data for pesticide residue prevention, management, control and monitoring in countries seeking to tighten pesticide standards.

Optimal Smoothing of the Wave Spectrum Using HeMOSU-1 Data

Lee, U.-J.; Lee, G.-S.; Ko, D.-H., and Cho, H.-Y., 2021. Optimal smoothing of the wave spectrum using HeMOSU-1 data. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 61–65. Coconut Creek (Florida), ISSN 0749-0208. An optimal model based on water surface elevation can be regarded as an optimal smoothing model, which estimates the optimal range of smoothing and can be considered a corresponding model. The optimal model is a process that classifies observation data either into a structure that can be statistically analyzed or into signal and noise components that can be given meaning, and the signal component becomes the optimal estimation model. In general, wave spectrum analysis is performed through water surface elevation data. In this study, the error generated during the process of smoothing the estimated spectrum is minimized by using a statistical estimation method that tracks the optimal bandwidth. For optimal smoothing, spectral data estimated through WaveGuide, a wave observation HeMOSU-1 device installed in Wido-Anmado, Southwest Korea were used. To optimize the estimated spectrum, the optimal bandwidth was estimated through the ‘locpoly’ function in the ‘KernSmooth’ package included in the R data analysis program, and the optimal smoothing with other functions was compared and analyzed. As a result of the analysis, the optimal bandwidth of the southwestern sea area, which was the analysis point, was estimated to be 0.021 ± 10%, and it was confirmed that the optimal bandwidth had a negative correlation with the wave height.

Assessment of metal contamination in sediments induced by small ships around lighters wharf in Southwest Korea

Assessment of metal contamination in sediments induced by small ships around lighters wharf in Southwest Korea

The relationship between resource abundance and insect herbivory on islands.

We examined the relationship between resource abundance and the feeding activity of phytophagous insects on three common island plants. The aim was to investigate the correlation between phytophagous insects' abundance and availability of food and island geography. We collected 30,835 leaves from three tree species groups (Mallotus japonicus, Prunus species, and Quercus species) on 18 islands in southwest Korea. The number of plant resources for herbivores varied: the number of leaves per shoot was the highest in Mallotus, leaf weight and the water content per leaf was significantly lower in Quercus species. External feeding was higher for Prunus and Quercus species, whereas the internal feeding type was significantly higher for Quercus species. Geography (area and distance), elevation and food resource (elevation, number of plant species, and the forest cover rate) had a variable effect on phytophagous insects feeding activities: distance and the number of plant species were more explainable to the external feeding guild. In contrast, area and forest cover were more to the internal feeding guild.

Magnetic Properties of a Holocene Sediment Core from the Yeongsan Estuary, Southwest Korea: Implications for Diagenetic Effects and Availability as Paleoenvironmental Proxies

The sensitivity of magnetic properties, which characterize the mineralogy, concentration, and grain size distribution of magnetic minerals, to environmental processes may provide useful information on paleoenvironmental changes in estuarine environments. Magnetic property studies of estuaries are less common than other environments and, due to the west coast of South Korea having an abundance of estuaries, it provides a good place to study these processes. In this study, we analyzed a variety of magnetic properties based on magnetic susceptibility, hysteresis parameters, progressive acquisition of isothermal remanent magnetization and first-order reversal curve data from a Holocene muddy sediment core recovered from the Yeongsan Estuary on the west coast of South Korea. We examined diagenetic effects on magnetic properties and tested their availability as proxies of paleoenvironmental change. The presence of generally low magnetic susceptibility, ubiquitous greigite-like authigenic magnetic component, and very fine magnetic particle occurrence suggested that the analyzed sediments had undergone considerable early diagenetic alteration. Electron microscopic observations of magnetic minerals support this suggestion. Our results confirm that the use of initial bulk susceptibility as a stand-alone environmental change proxy is not recommended unless it is supported by additional magnetic analyses. We recognized the existence of ferromagnetic-based variabilities related to something besides the adverse diagenetic effects, and have examined possible relationships with sea-level and major climate changes during the Holocene. The most remarkable finding of this study is the two distinct intervals with high values in magnetic coercivity (Bc), coercivity of remanence (Bcr), and ratio of remanent saturation moment to saturation moment (Mrs/Ms) that were well coincident with the respective abrupt decelerations in the rate of sea-level rise occurred at around 8.2 and 7 thousand years ago. It is then inferred that such condition with abrupt drop in sea-level rise rate would be favorable for the abrupt modification of grain size distribution toward more single-domain-like content. We modestly propose consideration of the Bc, Bcr, and Mrs/Ms variability as a potential indicator for the initiation/occurrence of sea-level stillstand/slowstand or highstand during the Holocence, at least at estuarine environments in and around the studied area.

Relationships between Alluvial Facies/Depositional Environments, Detrital Zircon U-Pb Geochronology, and Bulk-Rock Geochemistry in the Cretaceous Neungju Basin (Southwest Korea)

Zircon U-Pb geochronology and bulk-rock geochemistry analyses were carried out to investigate their relationship with depositional environments of the non-marine Neungju Basin sediments in South Korea. The Neungju Basin was formed in an active continental margin setting during the Late Cretaceous with associated volcanism. Detrital zircon age distributions of the Neungju Basin reveal that the source rocks surrounding the basin supplied sediments into the basin from all directions, making different zircon age populations according to the depositional environments. Mudstone geochemistry with support of detrital zircon U-Pb age data reveals how the heterogeneity affects the geochemical characteristics of tectonic setting and weathering intensity. The sediments in the proximal (alluvial fan to sandflat) and distal (playa lake) environments differ compositionally because sediment mixing occurred exclusively in the distal environment. The proximal deposits show a passive margin signature, reflecting their derivation from the adjacent metamorphic and granitic basement rocks. The distal deposits properly indicate an active continental margin setting due to the additional supply of reworked volcaniclastic sediments. The proximal deposits indicate a minor degree of chemical weathering corresponding to fossil and sedimentological records of the basin, whereas the distal deposits show lower weathering intensity by reworking of unaltered volcaniclastic detritus from unstable volcanic and volcaniclastic terranes. Overall, this study highlights that compositional data obtained from a specific location and depositional environments may not describe the overall characteristic of the basin.

Assessment of seismic vulnerability using the horizontal-to-vertical spectral ratio (HVSR) method in Haenam, Korea

The town of Haenam in southwest Korea lies partially on reclaimed coastal land and experienced an unprecedented earthquake swarm during April and May 2020. Construction of a new town in the area means that there is demand to evaluate the seismic hazard caused by site-specific amplification of seismic ground motions by artificial unconsolidated cover. We used a microtremor horizontal-to-vertical spectral ratio (HVSR) method to identify resonance frequencies, image depths to bedrock, and assess seismic ground vulnerability across the epicentral area of the recent earthquake swarm. Microtremor measurements were taken at 144 sites across an 18.5 km × 12.5 km study area. The HVSR analysis shows resonance frequencies as low as 1.1 Hz. Using mean shear-wave velocities obtained by Multi-Channel Analyses of Surface Waves (MASW), we find that resonance frequencies correspond to depths to bedrock of between 3 m and 56 m. There are clear relationships between the distribution of resonance frequencies, depths to bedrock, surface geology, and areas of development in recent land reclamation projects. Higher resonance frequencies characterize areas of thin sedimentary cover or hard rock sites, while relatively low resonance frequencies characterize reclaimed land or greater depths to bedrock. We quantify the seismic hazard potential across the study area using the seismic vulnerability of ground index (Kg), and observe a clear association between zones of high Kg and areas of reclaimed land. This study demonstrates the value of the HVSR technique in characterizing the subsurface and assessing seismic vulnerability in areas of reclaimed land, where it can be used as a viable and low-cost alternative to large-scale active seismic refraction or MASW measurements. The results can also be used to inform and guide urban planning projects.

Coastal landscape evolution tracked from late Holocene wave-cut benches in the Sinan Archipelago, Southwest Korea

Glacio-isostatic adjustment (GIA) and tectonic activity are important factors in the formation of marine terraces. Late Holocene wave-cut benches in the eastern part of the West Sea of Korea, also called the Yellow Sea, can be divided into two steps: 531 cm above sea level (ASL) for the upper bench (T2) and 464–481 cm ASL for the lower bench (T1). Sediments on the benches are classified into four units, and are interpreted to be beach deposits according to gravel shape, texture, and seaward inclination. The overlying sediment indicates that T2 was formed at approximately 530 cm ASL before 2900 yr BP, and T1 at approximately 460–480 cm ASL before 1520 yr BP. Late Holocene (4000–2000 yr BP) relative sea level (RSL) curves based on GIA models are inconsistent with the wave-cut bench elevations. Comparing T1 and T2 benches to the RSL curves of the West Sea, the upper and the lower benches were uplifted by approximately 5–8 m and 4–7 m, respectively. Although the area is several hundred kilometers away from plate boundaries, the high frequency of earthquakes in the West Sea may have induced the uplift of wave-cut benches during the last 2000 years. These indicate that the west coast of the Korean Peninsula (KP) should no longer be considered an area of subsidence, but be assigned to a regime of uplift during the late Holocene.

Late Pleistocene-Holocene sedimentary facies and evolution of the Jeju Strait shelf, southwest Korea

The depositional environments of the Jeju Strait shelf since the last interglacial period are analyzed using sedimentary structures, grain size textures, sediment color, and optically-stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) ages of vibro-cores. The shelf deposits can be divided into 12 sedimentary facies grouped into four depositional units: 1) shelf sand, 2) estuarine sand/mud, 3) fluvial sand/mud, and 4) shelf sand/mud. Each unit is separated by a sharp and unconformable erosion boundary. Unit 1 shows massive to slightly bedded sandy shells with oyster fragments, representing a shelf environment during sea-level highstand. The OSL date of the base of the unit is 124.4 ± 10.0 ka. Unit 2 is characterized by thin periodic parallel laminated mud, suggesting tidal signatures in tidal flats. Sediments are typically moderate brownish, suggesting extreme weathering after deposition. The OSL dates of this unit range from 81.1 ± 5.3 to 74.2 ± 4.7. Unit 3 consists of lower cross-bedded sand and laminated mud with fining-upward successions. It is interpreted as the product of channel deposits in a fluvial environment during a sea-level falling. The OSL ages of Unit 3 range from 50.6 ± 2.9 to 26.1 ± 1.6 ka, belonging to the Weichselian glacial period. The uppermost unit (Unit 4) is composed of homogeneous mud and massive sand with molluscan shell fragments in the modern shelf environment during sea-level highstand. OSL and 14C-AMS ages range from 0.32 ± 0.02 to 11.2 ± 0.1 ka. Consequently, the late Pleistocene-Holocene sedimentary facies in this area consist of marine and non-marine environments, which mainly correspond to sea-level changes.

Salirhabdus salicampi sp. nov., a halotolerant bacterium isolated from a saltern.

A Gram-stain-positive, halotolerant bacterium, designated strain BH128T, was isolated from soil of a saltern located at Bigeum Island in south-west Korea. Cells were aerobic, motile, spore-forming rods and grew at 15-53 °C (optimum, 35 °C), at pH 5.5-9.0 (optimum, pH 7.0) and at salinities of 0-16 % (w/v) NaCl (optimum, 8 % NaCl). The predominant isoprenoid quinone was menaquinone-7 (MK-7), and the cell-wall peptidoglycan type was A1γ, with meso-diaminopimelic acid as the diagnostic diamino acid. The major fatty acids were iso-C15 : 0, anteiso-C15 : 0, iso-C17 : 0 and anteiso-C17 : 0. The polar lipid pattern consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and four unknown phospholipids. The DNA G+C content was 36.5 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain BH128T belonged to the genus Salirhabdus and showed highest similarity to Salirhabduseuzebyi CVS-14T (95.8 %). On the basis of the phylogenetic, phenotypic and chemotaxonomic analyses in this study, strain BH128T is considered to represent a novel species of the genus Salirhabdus, for which the name Salirhabdussalicampi sp. nov. is proposed. The type strain is BH128T (=KACC 18690T=NBRC 111874T).

Integrated sedimentological and ichnological characteristics of a wave-dominated, macrotidal coast: a case study from the intertidal shoreface of the Dongho coast, southwest Korea

Generalized coastal facies models invariably assume that tidal flats and intertidally exposed shorefaces along macrotidal coasts are tide-dominated. Recent advances in coastal sedimentology, however, have revealed that wave-dominated macrotidal flats also occur in a wide range of coastal settings, in particular where tidal modulation forces the lateral translation of the wave-affected zone across the tidally exposed shoreface with the rising tide. Despite tidal modulation, the depositional character in the latter case (abundant storm deposits) exhibits a high degree of similarity with conventional subtidal shorefaces, implying that it is inherently difficult to distinguish between the two coastal systems in the rock record. In the present study, integrated sedimentological and ichnological data from the Dongho coast, which is located along the southwest coast of Korea, provide valuable information for the establishment of facies criteria that can assist in the recognition of such coastal deposits. In fact, the sedimentary character of the study area, which is dominated by an abundance of wave-formed structures, resembles that generally associated with subtidal shorefaces. In addition, the depositional processes responsible for sediment accumulation are, in the present case, also strongly influenced by pronounced seasonal variations in wave energy. In this context, the study has revealed a number of major features that appear to be characteristic of wave-dominated intertidal flats and shorefaces: (1) firmground muds may be encountered on the beach face, where intense swash-backwash motions are dominant; (2) the thickness of storm deposits decreases landward, reflecting the progressive decrease in wave energy; (3) ichnologically, there is an offshore shift in the dominance of trace fossils from the Skolithos ichnofacies, including Ophiomorpha, Thalassinoides and Psilonichnus, to a proximal expression of the Cruziana ichnofacies, which includes Siphonichnus and Asterosoma; (4) compared with subtidal shorefaces, the overall ichnological suite is represented by a substantial reduction in diversity and less uniformly distributed burrows. Although these findings have not yet been applied to the rock record, they should nevertheless assist in the distinction between corresponding coastal deposits.

Late Cretaceous volcanic arc system in southwest Korea: Distribution, lithology, age, and tectonic implications

In the southwestern part of the Korean Peninsula, Cretaceous volcanic rocks occur along a NE–SW-trending, sinistral strike-slip fault (Hamyeol Fault). Based on their spatial distribution, the volcanic rocks are classified into three lithostratigraphic units: the Buan, the Seonunsan, and the Beopseongpo Volcanics. These volcanics are composed of various types of pyroclastic, sedimentary, and lavas/intrusive rocks. SHRIMP UPb ages of zircon crystals were isolated from each unit. For the Buan Volcanics, Cheonmasan Tuff = 87.23 ± 0.92 Ma; Udongje Tuff = 86.79 ± 0.71 Ma; Seokpo Tuff = 87.30 ± 0.99 Ma; and Yujeongje Tuff = 86.66 ± 0.93 Ma. For the Seonunsan Volcanics, Gyeongsusan Tuff = 84.9 ± 1.1 Ma and Yeongije Tuff = 86.61 ± 0.67 Ma. For the Beopseongpo Volcanics, Seongsan Tuff = 87.73 ± 0.89 Ma and Gyema Rhyolite = 86.2 ± 1.7 Ma. The ages correspond well to recent mapping results of volcanic rocks in the southwest and south parts of the Korean Peninsula. In addition, the age data are comparable to those of the Aioi and Arima volcanic rock groups in southwestern Japan. This suggests that regional volcanic activity in the Japanese Islands and the southwestern part of the Korean Peninsula is related, and results from magmatism together with crustal deformation due to slab rollback of the Izanagi Oceanic Plate underneath the Eurasian Plate.

Textural variations and fragmentation processes in peperite formed between felsic lava flow and wet substrate: An example from the Cretaceous Buan Volcanics, southwest Korea

Multiple exposures of peperite within the Cretaceous Buan Volcanics, southwest Korea, have been examined in order to determine variations in their textural characteristics and to investigate their mode of formation. Along undulating boundaries between rhyolite (lava flow) and deformed host sediment expressed as a series of load and flame structures, exposures commonly contain two distinct types of peperite. Type-1 peperites are composed mostly of rounded juvenile clasts at their base and polyhedral juvenile clasts at their upper levels, interpreted to have formed via a two-stage process. Firstly, abrasion of juvenile clasts occurred after their fragmentation due to shear stress imparted by the overlying and still-moving lava flow, forming rounded juvenile clasts. Subsequent in situ quenching fragmentation of the lava flow produced clasts with platy to polyhedral shapes immediately after emplacement of the lava flow. Type-2 peperites laterally extend into the interior of featureless rhyolite as layers that decrease in thickness with increasing distance away from the flame zone. These layers exhibit horizontal textural variations, ranging from poorly sorted mixtures of ash- to block-sized angular juvenile clasts in the proximal zone, to closely packed polyhedral and tabular juvenile clasts with jigsaw-crack textures in the middle and distal zones. Type-2 peperite are inferred to have formed due to internal steam explosions that resulted from an expansion of heated pore water (leading to an increase in pore fluid pressure) that had been vertically injected into the interior of the rhyolite from the flame zone. The proximal zone, composed mainly of poorly sorted mixtures of juvenile clasts, represents the explosion sites. Juvenile clasts in the middle and distal zones are interpreted to have formed due to three separate processes: the development of fractures in the rhyolite during the internal steam explosions, injection of the host sediment through the fractures, and in situ quenching fragmentation. Deformation of the host sediment exerted an important control on peperite-forming processes, with the internal steam explosions suggested to have formed the closely packed, juvenile clasts with a jigsaw-crack texture rather than the clasts that are widely dispersed.

The Heuksan mud belt on the tide-dominated shelf of Korea: a supply-driven depositional system?

A 20–50-km-wide, approx. 200-km-long and 50-m-thick mud deposit around Heuksan Island, southwest Korea, extends from the mouth of the Geum River to the shelf off Jeju Island. The deposit formed in association with postglacial sea-level rise. However, the substantial thickness and rapid seaward progradation of the deposit over a period of only about 3–4 thousand years, as postulated by previous investigators, are difficult to reconcile with the rapid sea-level rise during the early to mid-Holocene. To resolve this discrepancy, the origin and stratigraphic evolution of the Heuksan mud belt were reexamined using high-resolution seismic profiles and three drill cores penetrating down to the basement. A sedimentary facies analysis with AMS 14C age control facilitated reconstruction of the postglacial evolution of the deposit. The seismic profiles reveal that the Heuksan mud deposit can be divided into three depositional events clearly defined by distinct spatiotemporal bounding surfaces. The lower unit contains retrograding tidal flat sequences formed during an earlier transgression commencing at ca.16.0 ka and terminating at 11.6 ka. The middle unit consists of rapidly prograding mud clinoforms deposited from 11–6.5 ka. This unit extends 80 km onto the distal shelf, and is characterized by sedimentation rates of 5.0 cm/year. From 6.5–6 ka, progradation was interrupted for a 500 year period during which the deposit retreated by 35 km due to a decrease in the sedimentation rate to 0.18 cm/year. The abrupt stratigraphic break was evidently triggered by a sudden change in sediment supply, resulting in rapid retreat of the unit despite continuing local sea-level rise. Renewed sedimentation commenced at about 6.0 ka, being initially characterized by clinoform progradation, followed by autoretreat from about 2.5 ka onward due to a decreasing sediment supply. The Heuksan mud belt may thus represent an example of a shelf depositional system driven predominantly by the rate of sediment supply, rather than by sea-level rise.

From Labour Control to Surplus Appropriation: Landscape Changes in the Neolithization of Southwestern Korea

The transformation of sociopolitical landscapes during the Mumun period (1300–100 BC) in southwest Korea is evidenced by major shifts in monumentality, mortuary activities and storage practices. This transformation is argued to represent one of the final stages in an extended process of Korean Neolithization that began much earlier with the adoption of pottery by hunter-gatherers and later saw the adoption and intensification of agriculture, triggering the rise of new forms of power and ideology. Importantly, elite groups employed a range of strategies to mask and then legitimate growing social inequality, generating major changes in human–landscape relations.

Vegetation history, agricultural intensification, and changes in wood-resource utilization in ancient Southwest Korea (1500 bc–ad 700)

An overview is presented of the analysis of wood remains at 11 archaeological sites in the southwestern region of the Korean Peninsula, and the results are used to shed light on the changes in wood-resource selection around the villages over the periods of c. 1500–300 bc and ad 1–700. Pollen research on swamps of the region has previously revealed that oak ( Quercus), alder ( Alnus), and pine ( Pinus) were the major woodland components, and that pine became increasingly prevalent after c. 1500 bc under the influence of agricultural expansion and climatic changes. Agricultural activities are represented by the dominance of grasses (Poaceae) in the pollen records. The wood collection underwent changes over time but not in direct response to the regional vegetation change. Wood was not randomly collected during the Mumun Period ( c. 1500–300 bc), with oak being preferentially selected despite the increasing dominance of pine. Chestnut tree ( Castanea crenata Siebold & Zucc.) was routinely used during and after the Proto-Three-Kingdoms Period ( c.ad 1–300) and was used almost exclusively at some sites. Such abundance suggests that the site occupants managed the neighboring forests and promoted the propagation of chestnut trees. Pinewood rarely appears in the retrieved samples, which suggests that the versatile use of pinewood is a relatively recent tradition in the Holocene history.

REVEGETATION OF DECOMPOSED GRANITE ROADCUTS IN KOREA: DEVELOPING DIGGER, EVALUATING COST EFFECTIVENESS, AND DETERMINING DIMENSIONS OF DRILLING HOLES, REVEGETATION SPECIES, AND MULCHING TREATMENT

ABSTRACTDecomposed granite roadcuts are difficult to revegetate after losing the topsoil and vegetation cover. We developed a new drilling machine, Digger, to efficiently drill six holes simultaneously on decomposed granite roadcuts to facilitate revegetation. The Digger consists of a base machine (0.7 m3‐level excavator) and a mounting body with six hydraulic motors instead of a bucket. We tested its performance on two roadcuts in southwest Korea using time‐motion studies, which showed that the Digger can drill 240 m2 of decomposed granite roadcuts daily. The unit cost of the Digger was less than a half of other roadcut stabilization and revegetation techniques in Korea, making the Digger a cost‐effective revegetation technology. Field germination and growth tests were also conducted to identify appropriate diameter and depth of drilling holes, suitable revegetation species, and mulching treatment. We drilled holes with three different diameters and depths, filled the holes with a mixture of plant seeds and cultivated soil, applied mulching treatments (coir geotextile, shade net, and no mulching), and measured the germination and growth results at two field plots after 1 month and 1 year. The results showed that drilling diameter 10 cm and depth 10 cm were large enough to result in better plant germination and growth. Erosion control species, Poa pratensis L. and Eragrostis curvula (Schrad.) Nees, survived and grew better than native woody species. Coir geotextile improved the plant germination and growth. The time‐motion and revegetation results show that the Digger can be a promising technology to restore decomposed granite roadcuts. Copyright © 2013 John Wiley & Sons, Ltd.

Pollen and sediment evidence for late-Holocene human impact at the Seonam-dong archeological site, Gwangju, Korea

We present pollen and sediment evidence for late-Holocene human impact from the Seonam-dong archeological site in Gwangju in southwest Korea. Due to the lack of undisturbed profiles with high sedimentation rates, the relationship between the environment and agricultural activities has not been properly investigated in Korea using a paleoenvironmental approach. This study shows possible climate-induced changes in chestnut production, which was contemporaneously recognized by the Chinese as an important and unique local food source in southwestern Korea. Our results also show that human adaptation to climate change may have resulted in both the degradation and recovery of the local forest ecosystem in the study area. The data from the Seonam-dong archeological site provided evidence supporting the following hypotheses. 1) Chestnut cultivation declined from 400 BC to AD 200 (2350–1750cal BP), as herbaceous crop production may have sufficiently expanded to sustain the population, possibly due to agricultural improvements and/or climatic amelioration. 2) Chestnut cultivation was enhanced from AD 200 to AD 800 (1750–1150cal BP), probably to compensate for decreased herbaceous crop yields due to climatic deterioration. 3) The increase in chestnut cultivation led to forest disturbance and increased flooding, with intermittent forest recovery during periods of decreased cultivation.

Tidal Current Energy Resources off the South and West Coasts of Korea: Preliminary Observation-Derived Estimates

In this study we estimate the prospective tidal current energy resources off the south and west coasts of Korea and explore the influence of modeling tidal current energies based on 15-day versus month-long data records for regimes with pronounced perigean/apogean influences. The tidal current energy resources off southern and western Korea were calculated using 29-day in situ observation data from 264 stations. The resultant annual energy densities found at each station were categorized into six groups, with a greater percentage of sites falling into the lower-energy groups: 1.1% for >10 MWh·m−2; 2.7% for 5 to 10 MWh·m−2; 6.8% for 3 to 5 MWh·m−2; 9.1% for 2 to 3 MWh·m−2 and 80.3% for <2 MWh·m−2. Analysis shows that the greatest concentration of high annual energy densities occurs in the Jeonnam Province coastal region on the western tip of southwest Korea: 23 MWh·m−2 at Uldolmok, 15 MWh·m−2 at Maenggol Sudo, 9.2 MWh·m−2 at Geocha Sudo and 8.8 MWh·m−2 at Jaingjuk Sudo. The second highest annual energy density concentration, with 16 MWh·m−2, was found in Gyudong Suro, in Gyeonggi Province’s Gyeonggi Bay. We then used data from the 264 stations to examine the effect of perigean and apogean influences on tidal current energy density evaluations. Compared to derivations using month-long records, mean annual energy densities derived using 15-day perigean spring-neap current records alone overestimate the annual mean energy by around 10% whereas those derived using only the apogean records underestimate energy by around 12%. In particular, accuracy of the S2 contribution to the energy density calculations is significantly affected by use of the 15-day data sets, compared to the M2 component, which is relatively consistent. Further, annual energy density estimates derived from 29-day records but excluding the N2 constituent underestimate the potential resource by about 5.4%. Results indicate that one month of data is required to accurately estimate tidal current energy in regimes showing pronounced perigean and apogean differences in spring-neap tidal current patterns and that inclusion of the N2 constituent in calculations is preferable. This finding has widespread applicability for green energy resource assessments, for example, in regions of the Unites States Atlantic coast and in New Zealand.