• Journal of Ecology and Environment
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• 제43권4호
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• pp.400-420
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• 2019

The aims of the study were to analyze (1) the effects of Prosopis juliflora (Prosopis) on the spatial distribution and soil seed banks (SSB) diversity and density, (2) the effects of environmental factors on SSB diversity and density (number of seeds in the soil per unit area), and (3) the effects of animal fecal droppings on SSB diversity, density, and dispersal. Aboveground vegetation data were collected from different Prosopis-infested habitats from quadrats (20 × 20 m) in Prosopis thickets, Prosopis + native species stand, non-invaded woodlands, and open grazing lands. In each Prosopis-infested habitats, soil samples were collected from the litter layer and three successive soil layer, i.e., 0-3 cm, 3-6 cm, and 6-9 cm. Seeds from soil samples and animal fecal matter were separated in the green house using the seedling emergence technique. Invasion of Prosopis had significant effects on the soil seed bank diversity. Results revealed that the mean value of the Shannon diversity of non-invaded woodlands was being higher by 19.2%, 18.5%, and 11.0% than Prosopis thickets; Prosopis + native species stand and open grazing lands, respectively. The seed diversity and richness, recovered from 6-9-cm-deep layer were the highest. On the other hand, the density of Prosopis seeds was the highest in the litter layer. About 156 of seeds/kg (92.9%) of seeds were germinated from cattle fecal matter. However, in a small proportion of seedlings, 12 of seeds/kg (7.1%) were germinated from shot fecal matter. Thus, as the seeds in the soil were low in the study areas, in situ and ex situ conservation of original plants and reseeding of persistent grass species such as Cynodon dactylon, Cenchrus ciliaris, Chrysopogon plumulosus, and Brachiaria ramosa are recommended.

• Geomechanics and Engineering
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• 제20권4호
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• pp.299-312
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• 2020

The aim of this paper was to investigating the effects of soil relative density, construction materials roughness, oil type (gasoil, crude oil, and used motor oil), and oil content on the internal and interface shear behavior of sand with different construction materials by means of a modified large direct shear test apparatus. Tests conducted on the soil-soil (S-S), soil-rough concrete (S-RC), soil-smooth concrete (S-SC), and soil-steel (S-ST) interfaces and results showed that the shear strength of S-S interface is always higher than the soil-material interfaces. Internal and interface friction angles of sand beds increased by increase in relative density and decreased by increasing oil content. The oil properties (especially viscosity) played a major role in interface friction behavior. Despite the friction angles of contaminated sands with viscous fluids drastically decreased, it compensated by the apparent cohesion and adhesion developed between the soil grains and construction materials.

• 한국농공학회지
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• 제11권4호
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• pp.1783-1790
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• 1969

It is one of the most economical method of soil stabilization works to compact soil, which increases soil density artificially. Compaction effort is to lessen void of soils, and consequently its aim is to enlarge friction and cohesion force, and reduce permeability of soil. Factors in compaction effort are moisture content, grain size, grain size distribution, physical properties, compaction method and temperature of soils etc. The results obtained in this study on the effects that grain size, gradation and physical properties influence upon compaction effort for 20 samples under the constant compaction method, are summarized as follows: 1. The bigger the maximum dry density is, the smaller the optimum moisture content is, on the other hand, the smaller the maximum dry densityis, the bigger the optimum moisture content is, ingeneral. 2. The coarser the grain size is, the bigger the maximum dry density is, and the optimum moisture content becomes small, and dry density-moisture content curve has the sharp peak, generally. Also, the finer the grain size is the smaller the maximum dry density is, and the optimum moisture content shows the big value, and dry density-moisture content curve has the dull peak. 3. The maximum dry density shows the biggest value on the sample to be about 15% of particles finer than No. 200 sieve. The more the percent passing of No. 10 sieve increase, the smaller the maximum dry density is. Soils which have uniformity coefficient less than 5 in particles larger than 0.074mm hardly show dry density-moisture content curve. 4. There is a relation which is ramax＝2.3948-0.0376 Wopt between the maximum dry density and the optimum moisture content, namely, the maximum dry density is increased in proportion to decrease of the optimum moisture content. 5. There are relations to be the straight lines which the maximum dry density decrease, on the other hand, the optimum moisture content increase in accordance with enlargement of Atterberg Limit(LL, PL, PL) in compacted soils.

• Journal of Forest and Environmental Science
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• 제29권1호
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• pp.29-37
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• 2013

The study was carried out in two different forest types viz., Banj oak and Chir pine forests to assess the variation in forest species composition and soil properties along altitudinal gradients in the Garhwal Himalayas. The results of the study showed that between the forests soil moisture was higher in Banj oak forest because of closed canopy and dense forest compared to Chir pine forest. The sand particles were reported higher in Banj oak forest which might be due to the addition of organic matter favouring coarse structure of soil, helping in holding maximum water in soils. However in the Chir pine forest low amount of soil organic matter and presence of clayey soil, develops soil compactness which reduces the penetration of water resulting in high soil bulk density. The higher accumulation of litter and presence of moisture in Banj oak forest favours higher nutrient level of nitrogen, phosphorus and potassium compared to Chir pine forest. The soil organic carbon also reduced with increasing altitude at both gradients. While bulk density has reverse trend with soil organic carbon in both the forests at different peaks of same region. In Banj oak forest, the highest density and total basal cover was reported 1,100 tree $ha^{-1}$ and 58.86 $m^2\;ha^{-1}$ respectively. However, the highest values of density and total basal cover of Chir pine forest was 560 tree$ha^{-1}$ and 56.94 $m^2\;ha^{-1}$ respectively. The total density and basal cover of both the forests reduced with increasing altitude. The study concludes that Banj oak forest has better nutrient cycling ability, well developed foest floor and has a greater protective and productive features compared to the Chir pine forest which is without lower vegetation cover and having only pine litter accumulation which does not allow any other species to grow.

• 한국토양동물학회지
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• 제1권1호
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• pp.37-47
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• 1996

This research was carried out to investigate soil mictoarthropods fauna in Namsan and Kwangreung which were considered to receive different degreeds of environmental pressures. In basic environmental data, Namsan where under rather accelerated acidification by air contamination and acidic rain showed low pH, tardy decomposition and turnover rate. Population density of soil microarthropods was high in Kwangreung 17,169.8/\ulcorner\ulcorner(coniferous forests), 17,892.6/$\textrm{m}^2$(deciduous forests) than in Namsan, 12,143.8/$\textrm{m}^2$ (coniferous forests), 14,216$\textrm{m}^2$(deciduous forests). Biomass of soil microarthropods was 2,020.219mg/$\textrm{m}^2$ at coniferous forests and 4,270.172mg/$\textrm{m}^2$ at deciduous forests in Namsan, and 3,287.326mg/$\textrm{m}^2$ at coniferous forests and 4326.1mg/$\textrm{m}^2$ at deciduous forests in Kwangreung. Population density constantly showed high in spring, and seasonal fluctuations were correlated with seasonal precipitation. As far as vertical distribution is concerned, population density was concentrated in litter layer as 70% while 30% are in soil layer and also decreased with increasing depth.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.239-244
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• 1999

In this study , the variation of dry density and unconfined compressive strength were investigated, calcium carbonate, quicklime, portland cement, 19mm monofilaments and fibrilllated fibers were used as reinforcement materials. And calcium chloride was added to cement and calcium carbonate reinforced soil mixture in order to accelerate setting and hardening speed. It appears that dry density is highest in calcium carbonate reinforced soil mixture with 9% of mixing rae. According to increasing the amount of fibers, in soil mixture , the dry density decreased. The more the amount of monofilament fibers is the higher the compressive strength. But the compressive strength is decreased in fibrrillated fiber added soil mixture with more than 1.0% of mixing rate.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.1117-1121
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• 2010

Several isotropic compression-expansion tests and a series of drained conventional traxial tests with various confining pressures for relative density of Beakma river sand 25%, 50%, 80% and 100% selecting Lade's Single Work-Hardening constitutive model. This examination materials use regression analysis as a basis, depending on the relative density of soil parameters change statement attributes. Yield fuction represent the soil parameters h and $\alpha$ is not affected by the changes in the relative density. $\eta_1$ could be replaced by fomula. And Numerical analysis results predicted very good and could confirm that.

• Current Research on Agriculture and Life Sciences
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• 제9권
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• pp.109-114
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• 1991

The depth and spread of root systems and the density of root branching affect the success and survival of plants subjected to drought. The type and size of root systems are controlled by heredity and soil conditions. There are also important interaction between roots and shoots; roots are dependent on shoots for carbohydrates, growth regulators, and certain vitamins, and shoots are dependent on roots for water, minerals, and certain growth regulators. Pinus thunbergii Parlatore had most of roots in the top 20cm of soil, and had little short of roots in the less than 80cm of soil. Average of root density was $270cm/cm^3$ in the upper soil(0~20cm). Root density of Pinus thunbergii Parlatore was similar to that of Cryptomeria japonica. There is no saying that Pinus thunbergii Parlatore has an advantage over Cryptomeria japonica in the drought. This data will be used to the root density values in the simulation model of black pine stands.

• 한국토양비료학회지
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• 제47권1호
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• pp.28-35
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• 2014

Due to recent interest of the consumers on safe farm products and the government's political support for eco-friendly agriculture, organic fruit production has been growing continuously. This research was conducted in order to study the effect of cover plants on soil microbial community on cover plants and establish an organic fruit cultivation method through choosing optimal cover plant. As a result of investigating soil microbial population density, the bacterial density in soil showed an increasing trend in June compared to April, and there was a decreasing trend in bacterial density of the soil in August compared to June. The density of actinomycetes in soil increased around 1.6 times in June compared to April when the soil was covered with hairy vetch. The increase of filamentous fungus in crimson clover group was 6.1 times higher in June compared to April and in hairy vetch group, the increase was 4.9 times higher in June compared to April. As a result of analyzing DNA extracted from the soil categorized by different types of cover plants using DGGE method, soil collected from April had higher number of bands detected from different locations according to different types of cover plants. Diversity of the bands from the soil collected from August showed higher range of reduction. As a result of analyzing soil microbial community by different period and the types of cover plants using Pyrosequencing method, microbes were detected in the order of Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, and Firmicutes. Distribution rate of Firmicutes increased in the soil collected in August compared to June and this was shown in all types of cover plants by twice the amount.

• Journal of Ecology and Environment
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• 제32권4호
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• pp.267-275
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• 2009

To investigate the possible applications of plants to remediate heavy-metal-contaminated soil, a pilot experiment was performed for four years in a reclaimed dredging area using two Alnus species, i.e., Alnus firma and Alnus hirsuta. In a comparison of phytomass of the two species at two different planting densities, the phytomass of Alnus planted at low density was twice as high as that of Alnus planted at high density after four years. The Alnus species showed active acclimation to the heavy-metal-contaminated soil in a reclaimed dredging area. A. hirsuta showed greater accumulation of phytomass than A. firma, indicating that it is the better candidate for the phytoremediation of heavy-metal-contaminated soils. In the pilot system, Alnus plants took metals up from the soil in the following order; Pb > Zn > Cu > Cr > As > Cd. Uptake rates of heavy metals per individual phytomass was higher for Alnus spp. planted at low density than those planted at high density in the pilot system. Low plant density resulted in higher heavy metal uptake per plant, but the total heavy metal concentration was not different for plants planted at low and high density, suggesting that the plant density effect might not be important with regard to total uptake by plants. The quantity of leached heavy metals below ground was far in excess of that taken up by plants, indicating that an alternative measurement is required for the removal of heavy metals that have leached into ground water and deeper soil. We conclude that Alnus species are potential candidates for phytoremediation of heavy-metal- contaminated surface soil in a reclaimed dredging area.