• Journal of Forest and Environmental Science
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• v.32 no.2
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• pp.205-211
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• 2016

Leaf chlorophyll content provides valuable information about physiological status of plants. However, fewer studies have investigated the difference in chlorophyll concentration in leaves of tropical afforestation tree species. Therefore, this study examines the difference in foliar chlorophyll contents of six tropical afforestation tree species namely: Tectona grandis, Pentaclethra macrophylla, Piptademiastrum africanum, Azadirachta indica, Brachystegia eurycoma and Gmelina arborea found in the relict forest in Umudike, South east, Nigeria. A single factor experiment in a completely randomised design in three replicates was employed to analyse the rate of leaf chlorophyll contents. Fisher's least significant different was used to test for significance in mean difference in foliar chlorophyll contents between tree species at 95% confidence interval using analysis of variance. The results of this study showed a significant difference in foliar chlorophyll concentration between the tree species with Tectona grandis having a higher chlorophyll concentration than other trees this could be as a result of its higher vegetative activity which increases its primary productivity followed by Pentaclethra macrophylla while Azadirachta indica having least the chlorophyll concentration. The study further revealed that other indigenous tree species like Piptademiastrum africanum and Brachystegia eurycoma have higher chlorophyll concentration. Further studies should be carry out to examine factors that have contributed informed the differences in the chlorophyll concentration of these trees species, thus this would broaden the understanding of their physiological status and equally encourage there conservation.

• Journal of Wetlands Research
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• v.13 no.1
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• pp.35-44
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• 2011

In order to explore vegetation adaptation to climate variability and the impacts on water balance dynamics, the inter-regional and the inter-annual variability of both water availability and vegetation productivity are investigated. The Horton index, which is the ratio between actual evapotranspiration and catchment wetting as a measure of vegetation water use at catchment-scale, is revisited to quantify the effects of growing-season water availability on hydrologic partitioning at catchment scale. It is shown that the estimated Horton index is relatively constant irrespective of inter-annual climate variability. In addition, the Horton index is compared with catchment-scale vegetation rain use efficiency. The results show that there is an interesting pattern in the response of vegetation water use to water availability. When water becomes the limiting factor for vegetation productivity, the catchment-scale vegetation rain use efficiency converges to a common maximum value in agreement with earlier findings at the ecosystem level.

• Korean Journal of Ecology and Environment
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• v.46 no.3
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• pp.319-331
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• 2013

Recent climate change, which is mostly ascribed to anthropogenic activities, is believed to be a major factor leading to biodiversity decreases and ecosystem service deteriorations. I have reviewed recent studies on climate change effects for many ecological processes involved with plants, in order to improve our understanding of the nature of ecological complexity. Plants in general have better growth and productivity under high levels of $CO_2$, although the long term effects of such $CO_2$ fertilizers are still controversial. Over the last 30 years, the Earth has been greening, particularly at higher latitudes of the Northern Hemisphere, perhaps due to a relaxation of climatic constraints. Human appropriation of net primary productivity (NPP), which corresponds up to 1/3 of global NPP, is ultimately responsible for climate change and biodiversity decreases. Climate change causes phenological variations in plants, especially in regards to spring flowering and fall leaf coloring. Many plants migrate polewards and towards higher altitudes to seek more appropriate climates. On the other hand, tree mortality and population declines have recently been reported in many continents. Landscape disturbance not only hinders the plant migration, but also makes it difficult to predict the plants' potential habitats. Plant and animal population declines, as well as local extinctions, are largely due to the disruption of species interactions through temporal mismatching. Temperature and $CO_2$ increase rates in Korea are higher than global means. The degree of landscape disturbances is also relatively high. Furthermore, long-term data on individual species responses and species interactions are lacking or quite limited in Korea. This review emphasizes the complex nature of species responses to climate change at both global and local scales. In order to keep pace with the direction and speed of climate change, it is urgently necessary to observe and analyze the patterns of phenology, migration, and trophic interactions of plants and animals in Korea's landscape.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.80-91
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• 2007

Crack in Pavements have been continually increased a by water penetration Therefore, the cracks can result in deterioration of the pavements that could be extremely dangerous fro road users. Creak sealing work performed in outdoor is very dangerous, costly and labor intensive. To slove these problems, automated crack sealing systems have been developed. it Would be needed that work information related to crack sealing must be gathered in an effort to used for existing or future crack sealing work. Furthermore, work information related to crack sealing could be utilized in analyzing work productivity and condition. The primary objective of this study is to propose a PDA and Web-based system for work information management of crack sealing which enables to effectively interchange work information between head office and fields, and to accurately collect work information. Finally, it is anticipated that the effective use of the developed PDA and web-based system would be able to effectively share work Information, measure productivity, estimate costs as well as plan future work schedule.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.6
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• pp.674-683
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• 2017

The frequency and intensity of soil moisture stress associated with climate change has increasing, and the stability of field crop cultivation has decreasing. This experiment was conducted to investigate the effect of soil moisture management method on growth and yield of corn. Soil moisture was managed at the grade of WSM (wet soil moisture, 34.0~42.9%), OSM (optimum soil moisture, 27.8~34.0%), DSM (dry soil moisture, 20.3~27.8%), and ESM (extreme dry moisture, 16.6~20.3%) during V8 (8th leaf stage)-VT (tasseling stage). After VT, irrigation was limited. The treated amount of irrigation was 54.1, 47.7, 44.0 and 34.5% of total water requirement, respectively. The potential evapotranspiration during the growing period was $3.29mm\;day^{-1}$, and upward movement of soil water was estimated by the AFKAE 0.5 model in the order of ESM, DSM, OSM, and WSM. We could confirm this phenomenon from actual observations. There was no significant difference in leaf characteristics, dry matter, and primary productivity depending on the level of soil moisture, but leaf development was delayed and dry weight decreased in DSM. However, dry weight and individual productivity of DSM increased after irrigation withdrawal compared to that of OSM. In DSM, ear yield and number of kernels per ear decreased, but water use efficiency and harvest index were higher than other treatments. Therefore, it is considered that the soil moisture is concentratedly managed before the V8 period, the V8-VT period is controlled within the range of 100 to 500 kPa (20.3~27.8%), and no additional irrigation is required after the VT.

• Journal of Korea Port Economic Association
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• v.37 no.3
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• pp.75-91
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• 2021

Due to increased competition in supply side to reduce operational costs, port professionals have experienced extreme pressure, which demanded academicians to develop the model for efficient port operations from the industry perspective. Among many ports in the world, U.S. ports are our primary interest to analyze in our study for its high volume of cargoes transacted in the U.S. ports. We primarily employed DEA (Data Envelopment Analysis) technique to research the productivity of U.S. ports and applied the algorithm of double bootstrapped DEA proposed by Simar & Wilson (2007) to further investigate the driving forces of the performance of U.S. port operations. The external variables employed in our study comprise onDock Rail, Channel Depth, Location, Area, Acres, ForeignCargoRatio, and TEUChange, out of which onDock Rail, Acres, ForeignCargoRatio, and TEUChange were significant. In order to evaluate the effects of methodology selection, we conducted the same analysis applying the Censored model (Tobit) and contrasted the outcomes drawn from the two different techniques. Based on the findings from this work we proposed managerial implications and concluded.

• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.657-666
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• 2022

Nitrogen (N) is a vital element in growing crops and is essential for improving the yield and quality of crops. Thus, N fertilizer is the most widely used fertilizer and the primary N input source in soil-crop systems. Inorganic fertilizers such as urea are known to improve crop productivity and increase soil fertility. However, application with excessive amounts can interfere with crop growth and accelerate soil acidification. For these reasons, the use of organic fertilizers, which mainly contain organic nitrogen, has gradually increased worldwide. Therefore, this study evaluated the effects of N fertilizer on the growth of Chinese cabbage including its functional compounds glucosinolates (GSLs). For the cultivation of Chinse cabbage, inorganic fertilizer was used for urea, and organic fertilizers were divided into conventional and biochar-based fertilizers. The growth parameters of Chinese cabbage treated by organic fertilizers was better than those of the inorganic fertilizers. Additionally, it was found that their co-application was more efficient. However, their GSL contents were lower with the application of the organic fertilizers. The characteristics of the experimental soil also changed according to the type, amounts and co-application of fertilizers. Therefore, this study presents the basis for an eco-friendly method that can increase the functionality and productivity of Chinese cabbage compared to conventional cultivations.

• Ocean and Polar Research
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• v.28 no.1
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• pp.1-12
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• 2006

Analyses of sedimentological and geochemical parameters from two radiocarbon-dated sediment cores (JM98-845-PC and JM98-818-PC) retrieved from the central part of Isfjorden, Svalbard, in the Arctic Sea, reveal detailed paleoclimatic and paleoceanographic histories over the last 15,000 radiocarbon years. The overconsolidated diamicton at the base of core JM98-845-PC is supposed to be a basal till deposited beneath pounding glacier that had advanced during the LGM (Last Glacial Maximum). Deglaciation of the fjord commenced after the glacial maximum, marked by the deposition of interlaminated sand and mud in the ice-proximal zone by subglacial meltwater discharge, and prevailed between 13,700 and 10,800 yr B.P. with enriched-terrigenous organic materials. A return to colder conditions occurred at around 10,800 yr B.P. with a drop in TOC content, which is probably coincident with the Younger Dryas event in the North Atlantic region. At this time, an abrupt decrease of TOC content as well as an increase in C/N ratio suggests enhanced terrigenous input due to the glacial readvance. A climatic optimum is recognized between 8,395 and 2,442 yr B.P., coinciding with 'a mid-Holocene climatic optimum' in Northern Hemisphere sites (e.g., the Laurentide Ice sheet). During this time, as the sea ice receded from the fjord, enhanced primary productivity occurred in open marine conditions, resulting in the deposition of organic-enriched pebbly mud with evidence of TOC maxima and C/N ratio minima in sediments. Fast ice also disappeared from the coast, providing the maximum of IRD (ice-rafted debris) input. Around 2,442 yr B.p. (the onset of Neoglacial), pebbly mud, characterized by a decrease in TOC content, reflects the formation of more extensive sea ice and fast ice, which might cause decreased primary productivity in the surface water, as evidenced by a decrease in TOC content. Our results provide evidence of climatic change on the Svalbard fjords that helps to refine the existence and timing of late Pleistocene and Holocene millennial-scale climatic events in the Northern Hemisphere.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.237-247
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• 1991

To characterize the community structure and spatial distribution of phytoplankton, observations on seawater temperature, salinity, nutrients, primary productivity and abundance and species composition of phytoplankton were made in the polar front region and its neighborhood off the east coast of Korea in summer 1990. Among the 96 taxa identified, Rhizosolenia setigera and Thalassionema nitzschioides were the most dominant species. The assemblage at the surface and 50 m depth was quite different in the northern inshore part of the study area but similar in the southern and offshore part. Principal component analysis by the species abundance showed that the phytoplankton consisted of the communities representing the surface of the northern inshore part with the neritic-warm dinoflagellates, the Northern Korean Cold Water with the cold water diatoms and the southern and offshore part, which seems to represent the Eastern Korean Warm Water, with the warm water diatoms. At the frontal region, diatoms were mixed with warm and cold water species. Primary productivity and phytoplankton standing crops were higher at the front than the neighboring waters. Nutrients were markedly high at the Northern Korean Cold Water. Horizontal advection of the Northern Korean Cold Water accompanied by nutrient supply seems to contribute to the high phytoplankton biomass at the front.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.3
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• pp.87-99
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• 2009

We evaluated modified Soil-Plant-Atmosphere model's performance to simulate the seasonal variation of net ecosystem exchange (NEE) of carbon and examined the critical controlling mechanism on carbon exchange using the model over a deciduous forest at Gwangnung in 2006. The modified Soil-Plant-Atmosphere (mSPA) model was calibrated to capture the mean NEE during the daytime (1000-1400 LST) and used to simulate gross primary productivity (GPP). Ecosystem respiration ($R_e$) has been estimated using an empirical formula developed at this site. The simulation results indicated that the daytime mean stomatal conductance was highly correlated with daily insolation in the summer. Low stomatal conductance in high insolation occurred on the days with low temperature rather than with high vapor pressure deficit. It suggests that the forest rarely experienced water stress in the summer of 2006. The model captured the observed bimodal seasonal variation with a mid-season depression of carbon uptake. The model estimates of annual GPP, $R_e$ and NEE were $964\;gC\;m^{-2}\;yr^{-1}$, $733\;gC\;m^{-2}\;yr^{-1}$, and $-231\;gCm\;^{-2}\;yr^{-1}$, respectively. Compared to the observed annual NEE, the modeled estimates showed more carbon uptake by about $140\;gC\;m^{-2}\;yr^{-1}$. The uncertainty of the estimate of annual NEE in a complex terrain is discussed.