SOOYOUN NAM - Academia.edu (original) (raw)
Papers by SOOYOUN NAM
Landscape and Ecological Engineering, 2016
Hydrological Processes, 2015
ABSTRACT Nutrient concentrations in stream water, rainfall, throughfall, stem flow, surface flow ... more ABSTRACT Nutrient concentrations in stream water, rainfall, throughfall, stem flow, surface flow and ground water were compared before, during, and after strip thinning (intensive 50%) in plantation forested watersheds in Tochigi, Japan. Influences were evaluated comparing four thinning-applied and two reference basins for one year before, six months during and one year after the thinning. Results show that this strip thinning significantly increased DTP, TP and DOC (DTP: 0.01 mg l-1, TP: 0.04 mg l-1, DOC: 0.53 mg l-1) during the thinning period and DTN and TN (DTN: 0.34 mg l-1, TN: 0.46 mg l-1) after the thinning in stream waters relative to the unthinned basins. The increased phosphorus during thinning indicated ground disturbances by the strip thinning, with a concomitant increase in DOC. Changes in biotic and abiotic conditions resulted in increased nitrogen after the thinning, particularly in the dissolved pool. Changes in hydrological processes due to thinning, e.g. a change in flow distributions (less high nutrient stem flow and more low nutrient throughfall) and an increase in water discharge in stream water, possibly weakened the direct influences of thinning on nutrient concentrations. This article is protected by copyright. All rights reserved.
Journal of Environmental Radioactivity, 2014
This study deals with the description of the vertical distribution of radiocaesium ( 137 Cs and 1... more This study deals with the description of the vertical distribution of radiocaesium ( 137 Cs and 134 Cs) in a representative coniferous forest soil, investigated 10 months after the Fukushima radioactive fallout. During soil sampling, the forest floor components (understory plants, litter (Ol-) and fermented layers (Of)) were collected and treated separately. The results indicate that radiocesium is concentrated in the forest floor, and high radiocesium transfer factor observed in the undergrowth plants (3.3). This made the forest floor an active exchanging interphase for radiocesium. The raw organic layer (Ol þ Of) holds 52% (5.3 kBq m À2 ) of the Fukushima-derived and 25% (0.7 kBq m À2 ) of the pre-Fukushima 137 Cs at the time of the soil sampling. Including the pre-Fukushima 137 Cs, 99% of the total soil inventory was in the upper 10 cm, in which the organic matter (OM) content was greater than 10%, suggesting the subsequent distribution most likely depends on the OM turnover. However, the small fraction of the Fukushimaderived 137 Cs at a depth of 16 cm is most likely due to the infiltration of radiocesium-circumscribed rainwater during the fallout before that selective adsorption prevails and reduces the migration of soluble 137 Cs. The values of the depth distribution parameters revealed that the distribution of the Fukushima-derived 137 Cs was somewhat rapid.
Landscape and Ecological Engineering, 2016
Hydrological Processes, 2015
ABSTRACT Nutrient concentrations in stream water, rainfall, throughfall, stem flow, surface flow ... more ABSTRACT Nutrient concentrations in stream water, rainfall, throughfall, stem flow, surface flow and ground water were compared before, during, and after strip thinning (intensive 50%) in plantation forested watersheds in Tochigi, Japan. Influences were evaluated comparing four thinning-applied and two reference basins for one year before, six months during and one year after the thinning. Results show that this strip thinning significantly increased DTP, TP and DOC (DTP: 0.01 mg l-1, TP: 0.04 mg l-1, DOC: 0.53 mg l-1) during the thinning period and DTN and TN (DTN: 0.34 mg l-1, TN: 0.46 mg l-1) after the thinning in stream waters relative to the unthinned basins. The increased phosphorus during thinning indicated ground disturbances by the strip thinning, with a concomitant increase in DOC. Changes in biotic and abiotic conditions resulted in increased nitrogen after the thinning, particularly in the dissolved pool. Changes in hydrological processes due to thinning, e.g. a change in flow distributions (less high nutrient stem flow and more low nutrient throughfall) and an increase in water discharge in stream water, possibly weakened the direct influences of thinning on nutrient concentrations. This article is protected by copyright. All rights reserved.
Journal of Environmental Radioactivity, 2014
This study deals with the description of the vertical distribution of radiocaesium ( 137 Cs and 1... more This study deals with the description of the vertical distribution of radiocaesium ( 137 Cs and 134 Cs) in a representative coniferous forest soil, investigated 10 months after the Fukushima radioactive fallout. During soil sampling, the forest floor components (understory plants, litter (Ol-) and fermented layers (Of)) were collected and treated separately. The results indicate that radiocesium is concentrated in the forest floor, and high radiocesium transfer factor observed in the undergrowth plants (3.3). This made the forest floor an active exchanging interphase for radiocesium. The raw organic layer (Ol þ Of) holds 52% (5.3 kBq m À2 ) of the Fukushima-derived and 25% (0.7 kBq m À2 ) of the pre-Fukushima 137 Cs at the time of the soil sampling. Including the pre-Fukushima 137 Cs, 99% of the total soil inventory was in the upper 10 cm, in which the organic matter (OM) content was greater than 10%, suggesting the subsequent distribution most likely depends on the OM turnover. However, the small fraction of the Fukushimaderived 137 Cs at a depth of 16 cm is most likely due to the infiltration of radiocesium-circumscribed rainwater during the fallout before that selective adsorption prevails and reduces the migration of soluble 137 Cs. The values of the depth distribution parameters revealed that the distribution of the Fukushima-derived 137 Cs was somewhat rapid.