• The Korean Journal of Ecology
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• 제27권4호
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• pp.225-230
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• 2004

The impact of slash and burning on microbial biomass C, N and P in soils of semi-evergreen tropical deciduous forest were studied from February 1999 to January 2000. The experimental sites were located near Moreh town in the Chandel district of Manipur state (India) along the Indo-Myanmar border between 23° 49' N-24°28'N latitude and 93°45'E-94°16'E longitude. Microbial biomass C ranged from 319.50 ㎍ g/sup -1/ 905.50㎍ g/sup -1/ in the slash and burnt site and from 209.50 ㎍ g/sup -1/ to 708.80 ㎍ g/sup -1/ soil in the forest site. Microbial N ranged from 19.30 ㎍ g/sup -1/ to 99.45 ㎍ g/sup -1/ in the slash and burnt site and from 16.08㎍ g/sup -1/ to 88.90 ㎍ g/sup -1/ in the forest site. Microbial P varied from 10.90 ㎍ g/sup -1/ to 32.21 ㎍ g/sup -1/ in the slash and burnt site and from 2.50 ㎍ g/sup -1/ to 17.60 ㎍ g/sup -1/ in the forest site in different months throughout the year. Microbial biomass C, N and P were recorded to be higher in the slash and burnt site compared to the forest site The conversion of forest into slash and burnt site for agriculture - the traditional shilling cultivation practiced by tribal people in the north- eastern India leads to addition of large amount of organic matter in the soil thereby exhibiting higher values of microbial biomass C, N and P in the recent slash and burnt site than that of the forest site. Relationship between the soil moisture, soil organic C and microbial biomass C, N and P were found to be correlated significantly in both the sites.

• Journal of Forest and Environmental Science
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• 제25권1호
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• pp.1-24
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• 2009

Teak (Tectona grandis) is one of the most valuable timber yielding species in the world, with predominant distribution in tropical or sub-tropical countries. However, natural teak available only in few countries like India, Myanmar, Laos People's Democratic Republic and Thailand. Teak grows well in deep, well-drained alluvial soils, fairly moist, warm, tropical climate with pH ranges from 6.5-7.5. Teak is cultivated in many Asian, African and South American countries for timber production. The global teak plantations are estimated to be three million hectare with major share in India (44%) followed by Indonesia (33%). India is considered as richest genetic resources of teak with large areas of natural teak bearing forests (8.9 million ha), plantations (1.5 million ha), clonal seed orchards (1000 ha) and seed production areas (5000 ha). The studies on diversity of teak populations showed that teak is an out crossing species with major portion of diversity present within the populations. The productivity and quality of teak timber varies depending upon the site and environmental conditions. Teak wood is moderately heavy, strong and tough,straight grained, coarse textured and ring porous with specific gravity varies from 0.55 to 0.70. The sapwood is white to pale yellow in colour and clearly demarcated while heartwood is dark brown or dark golden yellow in colour. Teak is one of the most durable timbers in the world, practically, impervious to fungus and white ant attack and resistant to decay. Teak wood is used in ship and boat constructions, furnitures and aesthetic needs. Genetic improvement programmes have been undertaken in countries like Thailand, India, Malaysia and Indonesia. The programme includes provenance identification and testing, plus tree selection and clonal multiplication, establishment of seed orchards and controlled hybridization. Several aspects like phenology, reproductive biology, fruit characteristics, silvicultural practices for cultivation, pest and diseases problems, production of improved planting stock, harvesting and marketing, wood properties and future tree improvement strategy to enhance productivity have been discussed in this paper.

• 한국토양비료학회지
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• 제30권2호
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• pp.168-177
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• 1997

열대지방인 라이베리아 Buchanan 지역의 수도작 시범농장 건설사업의 설계 및 영농 기초자료를 제공키 위해 토양조사를 실시하여 토양의 이화학적 특성과 수도재배에 미치는 영향에 대하여 연구하였으며 그 결과를 요약하면 다음과 같다. Plinthite를 갖는 Oxic B 층위가 30cm 이상이며 토양층위가 불명료하고 표토층의 유기물 함량이 낮은 Ochric A층을 나타내며 토양배수가 양호내지 약간 양호한 사양질 토양이다. 토양분류상 Ferralsols로 분류 할 수 있다. Plinthite가 균일하지는 않지만 전 층위를 통해 발견되며 공기에 노출될 경우 매우 단단해져 ironstone이 되었으며 특히 심토가 표토에 노출될 경우 수 시간 내에 매우 단단해지는 토양특성이 있다. 답작지로 개발 후 써레질이나 경운 등을 할 때 주의해야 할 사항이다. Plinthaquox로서는 점토함량이 낮은 편인데 이는 흰개미에 의해 지표 이하의 미립질 토양이 이동하여 흰개미집을 짓는데 이용되었기 때문일 것이다. 심토에는 Lateritic gravel인 Plinthite가 5~30% 가량 함유되어 있으며 기층에는 석영이 많이 함유된 Plinthite가 50% 이상이나 된다. 유효 Fe농도가 표토층에서 230~330mg/kg이고 심토층에서는 급격히 높아져 최고 2,200mg/kg까지 함유되어 있었다. 따라서 철분 독성이 심각하였으며 벼 재배시 벼가 수일 내에 황화현상을 일으켜 고사하였다. 흰개미집이 조사지역 내에 1ha 당 평균 14개나 분포되어 있으며, 이를 시범포 전 면적에 살포될 경우 약 1.2cm의 객토효과가 기대된다. 주변 토양보다 pH, 질소, 유효인산, 치환성염기가 현저히 높고 특히 Ca함량이 2,900mg/kg이나 되었으며 주변에 비해 매우 양호한 식생상태를 보였다. 철분독성에 대한 내성은 전반적으로 한국품종에 비해 라이베리아 품종이 강하였으며, 한국품종은 한강찰벼가, 라이베리아 품종은 Nizersail과 Suakoko 8이 강하였다. 따라서 본 시범포에서는 이 품종들이 추천되었다. 분포면적 가중평균 삼투량은 8.3mm/day이고 침입량은 2~2.5mm/hr 토양투수성이 양호한 편이다.

• 한국지반공학회논문집
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• 제15권5호
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• pp.193-204
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• 1999

흙의 파쇄성과 관련된 지반공학적 문제에 있어서 입상재료의 강도-변형특성을 해명하기 위한 중요한 인자의 하나로 흙입자의 파쇄를 들 수 있다. 최근, 열대ㆍ아열대 지방의 해안을 중심으로 거대한 해양 유전개발이 진행되고 있으며 이 지역에 넓게 분포된 카보네이트계 모래의 거동이 기존의 실리카계 모래의 거동에 비해 두드러지게 다르다는 것이 현장에서의 문제로 대두되고 있다. 본 연구에서는 흙의 파쇄성과 연관지어 입상재료의 역학특성을 정립하는 첫 단계로서, 흙 입자파쇄의 기본이 되는 개별입자의 파쇄 강도특성을 명백히 하기 위하여 4종류의 서로 다른 모래를 이용하여 단입자 파쇄시험을 수행하였다. 단입자 파쇄강도는 모래의 입자형상, 광물성분 및 입경의 영향을 고려하였으며, 입도분포 곡선의 $D_{50}$에 대응하는 흙입자 강도는 카보네이트성분의 함유량이 많을수록, 입자형상이 뾰족할수록 작은 값을 나타냈다.

• Asian-Australasian Journal of Animal Sciences
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• 제27권3호
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• pp.330-341
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• 2014

Andropogon gayanus is an important grass due to its high biomass production, drought tolerance and favorable growth on low fertility acidic soils. Currently, there is little research on the impact of growth stage on the nutritional quality or the degree of $CH_4$ production that may arise from this forage during ruminal fermentation. The objectives of this study were to determine the effects of regrowth stage of A. gayanus on its chemical composition, in vitro production of gas and CH4, as well as in vitro dry matter (DM) digestibility when grown under tropical Brazilian conditions and conserved as hay or as silage. The nutritional value of A. gayanus grass declined with increasing maturity; however digestible DM yield linearly increased. After 112 d of regrowth, A. gayanus produced higher quality silage (higher lactate and lower pH and butyrate content) and higher DM yield. However, the low levels of crude protein at this time would make protein supplementation a necessity for proper rumen fermentation. No differences in $CH_4$ kinetic parameters were found with advancing maturity or preservation method (hay or silage).

• The Plant Pathology Journal
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• 제20권4호
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• pp.240-243
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• 2004

White rot on Allium crops recently had a high incidence with incrensed cultivating areas of tropical garlic types in Korea. Two types of Sclerotium have known as causal agents that produce different size and shapes of sclerotia in infested fields. Therefore, we developed a new method for isolation of sclerotia from infested field soils that can be used for ecological study of Sclerotium spp. and establishment of control strategy. Soil samples collected from heavily infested fields were evenly mixed and placed on a automatic sieve shaker connected with tap water, After 10 min of shaking, residues on 0.5 mm and 0.25 mm sieves were separately collected and suspended with 70% sugar solution, which method floats sclerotia in aqueous layer, Then, floated fraction was carefully separated and mixed with a same volume of 1% sodium hypochlorite solution to differentiate with organic materials. This method provides a direct count of sclerotia under a dissecting microscopy.

• Journal of Forest and Environmental Science
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• 제34권5호
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• pp.359-375
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• 2018

The long term ecological effects have been reported in natural forest ecosystem due to various anthropogenic disturbances, especially in tropics of the world. The present study was carried out in the sanctuary area of central India to assess the changes on litter biomass, litterfall pattern and soil attributes under different disturbance regimes. The study area includes three forest circles i.e., Bhoramdeo, Jamunpani and Salehwara each comprising three disturbances regimes viz., high, medium and low severity of biotic pressure. A noticeable variation and impact were recorded in different sites. The impact varies significantly from least disturbed sites to highly disturbed sites across the circle and among different disturbances level. The seasonal mean total forest floor biomass across the forest circles varied from 2.18 to $3.30t\;ha^{-1}$. It was found highest under lightly disturbed site and lowest under heavily disturbed site. Total litterfall varied from 5.11 to $7.06t\;ha^{-1}\;yr^{-1}$ across the forest circle. Lowest litterfall was recorded at heavily disturbed site while highest in lightly disturbed site. Annual turnover of litter varied from 69-73% and the turnover time ranged between 1.37-1.45 years. The turn over time was higher for heavily disturbed site and lower for lightly disturbed site. The heavily disturbed site of all the circle showed the sandy loam soil texture, whereas moderately and lightly disturbed site comprised of sandy loam, sandy clay loam and clay soil texture, respectively. The bulk density decreases from heavily disturbed site to lightly disturbed site and the pH of soils ranged from 5.57-6.89 across the circle. Across the circle the total soil nitrogen ranged from 0.12-0.21%, phosphorus from 10.03-24.00 kg and Potassium from $139.88-448.35kg\;ha^{-1}$, respectively. Our results demonstrate that anthropogenic disturbances regime significantly influences forest floors in terms of mass, composition and dynamics along with litterfall rate and soil properties.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.120.1-120
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• 2003

White rot on Allium species recently had a high incidence as increased cultivating areas of tropical garlic types in Korea. Two types of Sclerotium have been known as causal agents producing different size and shapes of sclerotia in infested fields. We developed a new method for isolation of two types of sclerotia from infested field soils that can be used for ecological study of sclerotium spp. and establishment of control strategy. Soil samples collected from heavily infested fields were evenly mixed and placed on a automatic sieve shaker connected with tap water. After 10 min. of shaking, residues on 0.5mm and 0.25mm sieve were separately collected and suspended with 70％ sugar solution, which method floats sclerotia in aqueous layer. Then, floated fraction was carefully separated and mixed with a same volume of 1％ sodium hypochlorite solution to differentiate with organic materials. This method provides direct count of sclerotia under dissecting microscopy.

• Geomechanics and Engineering
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• 제8권5호
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• pp.649-661
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• 2015

This research provides insight on the laboratory investigation of the engineering properties of a lateritic soil modified with the mucilage of Opuntia ficus-indica cladodes (MOFIC), which has a history of being used as an earthen plaster. The soil is classified, according to AASHTO classification system, as A-2-6(1). The Atterberg limits, compaction, permeability, California bearing ratio (CBR) and unconfined compressive strength of the soil were determined for each of 0, 4, 8 and 12% addition of the MOFIC, by dry weight of the soil. The plasticity index, optimum moisture content, swell potential, unconfined compressive strength and permeability decreased while the soaked and unsoaked CBR increased, with increasing MOFIC contents. The engineering properties of the natural soil, which only satisfies standard requirements for use as subgrade material, became improved by the application of MOFIC such that it meets the standard requirements for use as sub-base material for road construction. The effects of MOFIC on the engineering properties of the soil resulted from bioclogging and biocementation processes. MOFIC is recommended for use as a modifier of the engineering properties of soils, especially those with similar characteristics to that of the soil used in this study, to be used as a pavement layer material. It is more economical and environment-friendly than conventional soil stabilizers or modifiers.

• Geomechanics and Engineering
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• 제20권3호
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• pp.221-232
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• 2020

In many tropical regions, soil structures often fail under constant loads as a result of decreasing matric suction due to water infiltration. Most of the previous studies have been performed by infiltrating water in the soil specimen by keeping shear stress constant at 85-90% of peak shear strength in order to ensure specimen failure during water infiltration. However, not many studies are available to simulate the soil behavior when water is infiltrated at lower shear stress and how the deformations affect the soil behavior if the failure did not occur during water infiltration. This research aimed at understanding both the strength and deformation behavior of unsaturated soil during the course of water infiltration at 25%, 50% and 75% of maximum deviatoric stress and axial strain by keeping them constant. A unique stress-strain curve expresses the transient situation from unsaturated condition to failure state due to water infiltration is also drawn. The shearing-infiltration test results indicate that the water infiltration reduces matric suction and increase soil deformation. This research also indicates that unsaturated soil failure problems should not always be treated as shear strength problems but deformation should also be considered while addressing the problems related to unsaturated soils.