• Environmental Engineering Research
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• v.23 no.1
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• pp.62-69
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• 2018

In the present study, long-term heavy metals (HMs) contaminated soil samples from a well-known Pb/Zn smelting area in the southwest of China were collected, and physicochemical and biological characteristics of these samples were evaluated. Soil samples contained different concentrations of HMs, namely Pb, Zn, Cu, and Cd. Enzyme activity analyses combined with microcalorimetric analysis were used for soil microbial activity evaluation. Results showed that two soil samples, containing almost the highest concentrations of HMs, also shared the greatest microbial activities. Based on correlation coefficient analysis, high microbial activity in heavily HMs contaminated soil might be due to the high contents of soil organic matter and available phosphorus in these samples. High-throughput sequencing technique was used for microbial community structure analysis. High abundance of genera Sphingomonas and Thiobacillus were also observed in these two heavily contaminated soils, suggesting that bacteria belonging to these two genera might be further isolated from these contaminated soils and applied for future studies of HMs remediation. Results of present study would contribute to the evaluation of microbial communities and isolation of microbial resources to remediate HMs pollution.

• The Korean Journal of Ecology
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• v.18 no.4
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• pp.503-512
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• 1995

The present paper describes partial results of the study on the activities of microbes in the soil of Quercus mongolica forest from July, 1994 to April, 1995. To determine the relationship between structure and function of soil microbial ecosystem, the author investigated the seasonal change of physical environmental factors, microbial population and soil enzyme activities. The changes of pH was not significant and the temperature of surface soil was 2℃ higher than lower soil through out the year. Moisture contents (％) of soil samples ranged from 7.64％ to 42.11％. However, soils of site 3 at Mt. Komdan in which vegetation is successional have higher moisture content than the others. The bacterial population increased in summer, but continuously decreased in autumn and winter, and then reincreased again in spring. Bacterial population of surface soil was higher than those of 30 cm depth all the year round. Dehydrogenase activity (DHA) was about two-fold higher throughout in surface soil compared to those of lower soil. And the correlation coefficient between DHA and bacterial population size was 0,713, It was suggested that DHA could be used as a primary index of soil microbial population and activity in soil ecosystem.

• Journal of Soil and Groundwater Environment
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• v.28 no.5
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• pp.68-77
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• 2023

The effect of soil damage on the physicochemical characteristics and activity of the soil microbial community is not well known. This study investigates this relationship by analyzing 11 soil samples collected from various points of soil damage across Gyeonggi-do. Soil damage resulted from forest fires, landslides, and development areas, with their impacts most severe on the topsoil layer (0-30 cm). Dehydrogenase and β-glucosidase activities were notably higher at locations damaged by forest fires compared to other sites. While enzyme activities in soils influenced by landslides and development areas were relatively low, sites with a pollution history exhibited elevated dehydrogenase activity, likely due to past microbial response to the pollution. Additionally, an assessment of carbon substrate usability by soil microorganisms indicated higher substrate availability in areas impacted by forest fires, contrasting with lower availability in landslide and development sites. Statistical analysis revealed a positive correlation between organic content of sand and clay and microbial activity. These findings provide valuable insights into soil damage and associated restoration research, as well as management strategies.

• Journal of Microbiology
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• v.42 no.4
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• pp.267-277
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• 2004

Effects of elevated $CO_2$ on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and syn­thesize results from studies assessing impacts of elevated $CO_2$ on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated $CO_2$ in atmosphere may enhance certain micro­bial processes such as $CH_4$ emission from wetlands due to enhanced carbon supply from plants. How­ever, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of $CO_2$ fumigation systems are not fully understood.

• Journal of Ecology and Environment
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• v.33 no.2
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• pp.133-139
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• 2010

Atmospheric $CO_2$ concentrations have increased exponentially over the last century and, if continued, are expected to have significant effects on plants and soil. In this study, we investigated the effects of elevated $CO_2$ on the growth of Pinus densiflora seedling and microbial activity in soil. Three-year-old pine seedlings were exposed to ambient as well as elevated levels of $CO_2$ (380 and 760 ppmv, respectively). Growth rates and C:N ratios of the pine seedlings were also determined. Dissolved organic carbon content, phenolic compound content, and microbial activity were measured in bulk soil and rhizosphere soil. The results show that elevated $CO_2$ significantly increased the root dry weight of pine seedling. In addition, overall N content decreased, which increased the C:N ratio in pine needles. Elevated $CO_2$ decreased soil moisture, nitrate concentration, and the concentration of soil phenolic compounds. In contrast, soil enzymatic activities were increased in rhizosphere soil, including ${\beta}$-glucosidase, N-acetylglucosaminidase and phosphatase enzyme activities. In conclusion, elevated $CO_2$ concentrations caused distinct changes in soil chemistry and microbiology.

• Korean Journal of Environment and Ecology
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• v.26 no.6
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• pp.902-910
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• 2012

This study has been carried out to determine the effects of disturbances from wild boar grubbing on the functions of ecosystem. The experiments was performed in Mt. Jumbong of Long-term Ecological Research Sites of the Ministry of Environment. We measured soil physical properties, soil respiration($CO_2$), microbial biomass C, and soil enzyme activities from both disturbed and control plots. The disturbance sites were divided into two parts, mounds and pits. Soil organic matter contents were highest value at the control plots and lowest at the pit plots, respectively at 20.22% and 15.52%. The soil bulk densities were highest at the pit plots. Soil microbial biomass C and $CO_2$ evolution were significantly higher at the control plots compared to the disturbed plots. The results were positively correlated with soil organic matter contents. The cellulase activity and invertase activity in the soil showed similar pattern as the microbial biomass C and $CO_2$ evolution results. The cellulase activity and invertase activity in the soil were positively correlated with soil microbial biomass C. Soil organic matter contents seemed to affect the soil enzyme activities. The nitrate reductase activities were highest at the pit plots, which showed positive correlation with soil bulk density. The study results showed that the grubbing disturbances by wild boars induced the changes in soil properties, which affected soil microbial activities.

• Journal of Microbiology and Biotechnology
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• v.33 no.6
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• pp.760-770
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• 2023

Continuous cropping obstacles have become a serious factor restricting sustainable development in modern agriculture, while companion planting is one of the most common and effective methods for solving this problem. Here, we monitored the effects of companion planting on soil fertility and the microbial community distribution pattern in pepper monoculture and companion plantings. Soil microbial communities were analyzed using high-throughput sequencing technology. Companion plants included garlic (T1), oat (T2), cabbage (T3), celery (T4), and white clover (T5). The results showed that compared with the monoculture system, companion planting significantly increased the activities of soil urease (except for T5) and sucrase, but decreased catalase activity. In addition, T2 significantly improved microbial diversity (Shannon index) while T1 resulted in a decrease of bacterial OTUs and an increase of fungal OTUs. Companion planting also significantly changed soil microbial community structures and compositions. Correlation analysis showed that soil enzyme activities were closely correlated with bacterial and fungal community structures. Moreover, the companion system weakened the complexity of microbial networks. These findings indicated that companion plants can provide nutrition to microbes and weaken the competition among them, which offers a theoretical basis and data for further research into methods for reducing continuous cropping obstacles in agriculture.

• Journal of Plant Biotechnology
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• v.44 no.2
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• pp.156-163
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• 2017

A greenhouse experiment was conducted for evaluation of ecological effects of transgenic melon plants in the rhizospheric soil in terms of soil properties, enzyme activities and microbial communities. Organic matter content of soil under transgenic melon plants was significantly higher than that of soil with non-transgenic melon plants. Significant variations were observed in organic matter, total P and K in soil cultivation with transgenic melon plants. There were also significant variations in the total numbers of colony forming units of fungi, actinomycetes and bacteria between soils treated with transgenic and non-transgenic melon plants. Transgenic and non-transgenic melon significantly enhanced several enzymes activities including urease, acid phosphatase, alkalin phosphatase, arysulphtase, ${\beta}$ glucosidase, dehydrogenase, protease and catalase. Soil polyphenoloxidase activity of $T_1$ transgenic melon was lower than that of $T_0$ transgenic melon and a non-melon plant during the same period. The first generation transgenic melon plants ($T_0$) showed significantly greater (p<0.05) effect on the activitiy of arylsulfatase, which increased from $2.540{\times}10^6CFU\;g^{-1}$ (control) to $19.860{\times}10^6CFU\;g^{-1}$ ($T_0$). These results clearly indicated that transgenic melon might change microbial communities, enzyme activities and soil chemical properties.

• The Korean Journal of Ecology
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• v.21 no.5_3
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• pp.695-702
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• 1998

This study was carried out to investigate to determine seasonal variation of dehydrogenase activity, phosphatase activity, adenosine tri-phosphate content and some physicochemical properties, such as soil pH, moisture content, organic matter and several heavy metal concentrations from Apr. 1997 to jan. 1998 in Pinus densiflora and Quercus mongolica forest in Mt. Nam, to explain a relationship between enzyme activity and the soil factors. There were ranges of 4.03-4.65 in soil pH, 18.65-51.09% in moisture content and 6.69-95.95% in orgainc matter. The organic matter content decreased with soil horizon, showing the higher values in Q. mongolica forest. In comparison to the results of Kawngneung site as control area, there were slightly differences due to a development level of forest ecosystem and microbial degradation of organic matter. The heavy metal concentrations showed 32.50-75.55 ${\mu}g/g$ in Cu, 69.33-134.84 ${\mu}g/g$ in Zn, 57.02-150.32 ${\mu}g/g$ in Pb, and 0.36-1.00 ${\mu}g/g$ in Mt. Nam. These values are higher than in Kwangneung site because of long-term exposure to air pollutants from central city. On the other hand, ATP contents in Mt. Nam were lower than in Kawngneung site in relation to soil organic matter, moisture content and relatively high heavy metal concentrations. ATP contents per soil weight was largest in F+H layer and in spring time of other seasons. Dehydrogenase activity as an index of soil microbial activity had a ranges of 170.67-1,221.66 ${\mu}g$ TPF/g that showed lower values than in Kawngneung site. However, phophatase activity had a contray tendency due to P fertilization for a continuous management. Those values increased through spring to a maximum in the summer and fall in autumn. This is basically caused by metabolic state of soil on the biological activity and several and several factors, such as aeration, soil temperature, vegetation and microflora.

• Journal of Ecology and Environment
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• v.34 no.3
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• pp.315-322
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• 2011

We investigated the effect of Pb uptake by Pinus densiflora and the Pb fraction in forest soil. We also investigated the change in soil physicochemical characteristics, microbial activity, and root exudates of Pinus densiflora in Pb-contaminated soils. Three-year-old pine seedlings were exposed to 500 mg/kg Pb for 12 months. The metal fractions were measured using sequential extraction procedures. Additionally, factors that affect solubility (three soil enzyme activities and amino acids of root exudate compounds) were also determined. The results showed that Pb contamination significantly decreased enzyme activities due to soil characteristics. In addition, organic matter, nitrate content, and Pb concentration were time dependent. The results indicate that changes in the Pb fraction affected Pb uptake by pine trees due to an increase in the exchangeable Pb fraction. The concentrations of organic acids were higher in Pb-spiked soil than those in control soil. Higher rhizosphere concentrations of oxalic acid resulted in increased Pb uptake from the soil. These results suggest that pine trees can change soil properties using root exudates due to differences in the metal fraction.