• Journal of Ecology and Environment
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• v.44 no.2
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• pp.81-89
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• 2020

In the forest ecosystems, litterfall is an important component of the nutrient cycle that regulates the accumulation of soil organic matter (SOM), the input and output of the nutrients, nutrient replenishment, biodiversity conservation, and other ecosystem functions. Therefore, a profound understanding of the major processes (litterfall production and its decomposition rate) in the cycle is vital for sustainable forest management (SFM). Despite these facts, there is still a limited knowledge in tropical forest ecosystems, and further researches are highly needed. This shortfall of research-based knowledge, especially in tropical forest ecosystems, may be a contributing factor to the lack of understanding of the role of plant litter in the forest ecosystem function for sustainable forest management, particularly in the tropical forest landscapes. Therefore, in this paper, I review the role of plant litter in tropical forest ecosystems with the aims of assessing the importance of plant litter in forest ecosystems for the biogeochemical cycle. Then, the major factors that affect the plant litter production and decomposition were identified, which could direct and contribute to future research. The small set of studies reviewed in this paper demonstrated the potential of plant litter to improve the biogeochemical cycle and nutrients in the forest ecosystems. However, further researches are needed particularly on the effect of species, forest structures, seasons, and climate factors on the plant litter production and decomposition in various types of forest ecosystems.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.318-326
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• 2017

Riverine wetlands were reduced and damaged by dredging of rivers and constructing parks in wetlands by Four Rivers Project from 2008 to 2013. Therefore, replacement wetlands were constructed for the compensation of wetland loss by the government. However, It is not enough to manage replacement wetlands. In order to manage the wetlands efficiently, it is necessaty to assess the functions of the wetlands and to manage them according to their functions. Here we performed functional assessments for a replacement wetland called Gangcheon wetland using the modified HGM approach. Hydrological, biogeochemical, animal habitat, and plant habitat functions for the wetland were assessed. To assess the functions, we collected informations for modified HGM approach from the monitored hydrologic data, field survey, published reports and documents for before and after the project, and hydraulic & hydrologic modeling. As the results of the assessment, the hydrological function for the replacement wetland showed 65.5% of the reference wetland, biogeochemical function showed 66.6%, plant habitat function showed 75%, and animal habitat function showed 108.3%. Overall, Gangcheon wetland function after the project was reduced to 78.9% of the function before the project. The decrease in hydrological function is due to the decrease of subsurface storage of water. And the decrease in biogeochemical & pland habitat functions is due to the removal of sandbank around the Gangcheon wetland. To compensate for the reduced function, it is necessary to expand the wetland area and to plant the various vegetation. The modified HGM used in this study can take into account the degree of improvement for replacement wetlands, so it can be used to efficiently manage the replacement wetlands. Also when the wetland is newly constructed, it will be very useful to assess the change of function of the wetland over time.

• Journal of Korean Society of Forest Science
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• v.99 no.2
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• pp.163-171
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• 2010

Forest fires have potentials to change the structure and function of forest ecosystems and significantly influence on atmosphere and biogeochemical cycles. Forest fire also affects the quality of public benefits such as carbon sequestration, soil fertility, grazing value, biodiversity, or tourism. The prediction of fire occurrence and its spread is critical to the forest managers for allocating resources and developing the forest fire danger rating system. Most of fires were human-caused fires in Korea, but meteorological factors are also big contributors to fire behaviors and its spread. Thus, meteorological factors as well as social factors were considered in the fire danger rating systems. A total of 298 forest fires occurred during the fall season from 2002 to 2006 in South Korea were considered for developing a logistic model of forest fire occurrence. The results of statistical analysis show that only effective humidity and temperature significantly affected the logistic models (p<0.05). The results of ROC curve analysis showed that the probability of randomly selected fires ranges from 0.739 to 0.876, which represent a relatively high accuracy of the developed model. These findings would be necessary for the policy makers in South Korea for the prevention of forest fires.

• Journal of Microbiology and Biotechnology
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• v.34 no.3
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• pp.580-588
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• 2024

Microbial communities in mangrove forests have recently been intensively investigated to explain the ecosystem function of mangroves. In this study, the soil microbial communities under young (<11 years-old) and old (>17 years-old) mangroves have been studied during dry and wet seasons. In addition, biogeochemical properties of sediments and methane emission from the two different mangrove ages were measured. The results showed that young and old mangrove soil microbial communities were significantly different on both seasons. Seasons seem to affect microbial communities more than the mangrove age does. Proteobacteria and Chloroflexi were two top abundant phyla showing >15%. Physio-chemical properties of sediment samples showed no significant difference between mangrove ages, seasons, nor depth levels, except for TOC showing significant difference between the two seasons. The methane emission rates from the mangroves varied depending on seasons and ages of the mangrove. However, this did not show significant correlation with the microbial community shifts, suggesting that abundance of methanogens was not the driving factor for mangrove soil microbial communities.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.56-68
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• 2005

We measured nitrate and other nutrients in sediment pore waters retrieved from three sites at the southern upper-tidal flats of the Ganghwa Island. Denitrification rate is estimated by applying a simple 1-D model to the nitrate profiles. Results from Jangwha and Dongmak sites are $7.8{\sim}9.4{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, and $1.4{\sim}3.6{\times}10^{-7}{\mu}mol{\cdot}cm^{-2}{\cdot}sec^{-1}$, respectively. Rates are comparable to those reported around the world in an order of magnitude. Denitrification was lower in summer. The rates were about 1.5 times higher at site where the surface sediments consist of relatively coarser particles. This implies that particle size would control the reactant supply to the subsurface sediment. One may claim the denitrification as an evidence of the biogeochemical purification function of tidal flat. However, the purification seems not a general attribute of a tidal flat when whole system is scrutinized by a thermodynamic criterion. Currently the term 'tidal flat' is used when describing the diverse coastal wetlands such as salt marshes, sandy tidal flats and muddy tidal flats, which exhibit quite different ecological functions. Thus it is worthy of mentioning that the classification of coastal wetlands on the basis of sedimentological characteristics and biogeochemical functions should facilitate our understanding.

• Economic and Environmental Geology
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• v.47 no.1
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• pp.61-69
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• 2014

As we are trying to in-situ treat (purify or immobilize) heavy metals or radionuclides in groundwater, one of the geochemical factors to be necessarily considered is the value of oxidation/reduction potential (ORP) of the groundwater. A biogeochemical impact on the characteristic ORP change of groundwater taken from the KAERI underground was observed as a function of time by adding electron-donor (lactate), electron-acceptor (sulfate), and indigenous bacteria in a laboratory condition. There was a slight increase of Eh (slow oxidation) of the pure groundwater with time under a $N_2$-filled glove-box. However, most of groundwaters that contained lactate, sulfate or bacteria showed Eh decrease (reduction) characteristics. In particular, when 'Baculatum', a local indigenous sulfate-reducing bacterium, was injected into the KAERI groundwater, it turned to become a highly-reduced one having a decreased Eh to around -500 mV. Although the sulfate-reducing bacterium thus has much greater ability to reduce groundwater than other metal-reducing bacteria, it surely necessitated some dissolved ferrous-sulfate and finally generated sulfide minerals (e.g., mackinawite), which made a prediction for subsequent reactions difficult. As a result, the ORP of groundwater was largely affected even by a slight injection of nutrient without bacteria, indicating that oxidation state, solubility and sorption characteristics of dissolved contaminants, which are affected by the ORP, could be changed and controlled through in-situ biostimulation method.

• Journal of Microbiology and Biotechnology
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• v.30 no.9
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• pp.1355-1366
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• 2020

Sediment bacterial communities are critical to the biogeochemical cycle in river ecosystems, but our understanding of the relationship between sediment bacterial communities and their specific input streams in rivers remains insufficient. In this study, we analyzed the sediment bacterial community structure in a local river receiving discharge of urban domestic sewage by applying Illumina MiSeq high-throughput sequencing. The results showed that the bacterial communities of sediments samples of different pollution types had similar dominant phyla, mainly Proteobacteria, Actinobacteria, Chloroflexi and Firmicutes, but their relative abundances were different. Moreover, there were great differences at the genus level. For example, the genus Bacillus showed statistically significant differences in the hotel site. The clustering of bacterial communities at various sites and the dominant families (i.e., Nocardioidaceae, and Sphingomonadaceae) observed in the residential quarter differed from other sites. This result suggested that environmentally induced species sorting greatly influenced the sediment bacterial community composition. The bacterial co-occurrence patterns showed that the river bacteria had a nonrandom modular structure. Microbial taxonomy from the same module had strong ecological links (such as the nitrogenium cycle and degradation of organic pollutants). Additionally, PICRUSt metabolic inference analysis showed the most important function of river bacterial communities under the influence of different types of domestic sewage was metabolism (e.g., genes related to xenobiotic degradation predominated in residential quarter samples). In general, our results emphasize that the adaptive changes and interactions in the bacterial community structure of river sediment represent responses to different exogenous pollution sources.

• Korean Journal of Environmental Biology
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• v.30 no.2
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• pp.77-89
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• 2012

With the advent of the genomics era powered by DNA sequencing technologies, life science is being transformed significantly and biological research and development have been accelerated. Environmental biology concerns the relationships among living organisms and their natural environment, which constitute the global biogeochemical cycle. As sustainability of the ecosystems depends on biodiversity, examining the structure and dynamics of the biotic constituents and fully grasping their genetic and metabolic capabilities are pivotal. The high-speed high-throughput next-generation sequencing can be applied to barcoding organisms either thriving or endangered and to decoding the whole genome information. Furthermore, diversity and the full gene complement of a microbial community can be elucidated and monitored through metagenomic approaches. With regard to human welfare, microbiomes of various human habitats such as gut, skin, mouth, stomach, and vagina, have been and are being scrutinized. To keep pace with the rapid increase of the sequencing capacity, various bioinformatic algorithms and software tools that even utilize supercomputers and cloud computing are being developed for processing and storage of massive data sets. Environmental genomics will be the major force in understanding the structure and function of ecosystems in nature as well as preserving, remediating, and bioprospecting them.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.1 no.1
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• pp.58-67
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• 2020

Terrestrial ecosystems influence climate change via their climate regulation function, which is manifested within the carbon, water, and energy circulation between the atmosphere and surface. However, it has been challenging to quantify the climate regulation of terrestrial ecosystems and identify its regional distribution, which provides useful information for establishing regional climate-mitigation plans as well as facilitates better understanding of the interactions between the climate and land processes. In this study, a land surface model (LSM) that represents the land-atmosphere interactions and plant phenological variations was introduced to assess the contributions of terrestrial ecosystems to atmospheric warming or cooling effects over East Asia over the last half century. Three main climate-regulating components were simulated: net radiation flux, carbon exchange, and moisture flux at the surface. Then, the contribution of each component to the atmospheric warming or cooling (negative or positive feedback to the atmosphere, respectively) was investigated. The results showed that the terrestrial ecosystem over the Siberian region has shown a relatively large increase in positive feedback due to the enhancement of biogeochemical processes, indicating an offset effect to delay global warming. Meanwhile, the Gobi Desert shows different regional variations: increase in positive feedback in its southern part but increase in negative one in its eastern part, which implies the eastward movements of desert areas. As such, even though the LSM has limitations, this model approach to quantify the climate regulation is useful to extract the relevant characteristics in its spatio-temporal variations.

• Korean Journal of Remote Sensing
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• v.26 no.5
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• pp.537-547
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• 2010

The importance of vegetation in studies of global climate and biogeochemical cycles is well recognized. Especially. the FPAR (fraction of photosynthetically active radiation) is one of the important parameters in ecosystem productivity and carbon budget models. Therefore, accurate estimates of vegetation parameters are increasingly important in environmental impact assessment studies. In this study, optical FPAR using the Terra MODIS (MODerate resolution Imaging Spectroradiometer), SPOT VEGETATION and ECOCLIMAP data reproduced on the Korean peninsula. We applied the empirical method which is usually estimated as a linear or nonlinear function of vegetation indices. As results, we estimated the accurate expression which is 0.9039 of $R^2$ in cropland and 0.7901 of $R^2$ in forest. Finally, this study could be demonstrated to calibrate that produced FPAR while the overall pattern and random noise through the comparative analysis of FPAR on the reference data. Optimal use of input parameter on the Korean peninsula should be helping the accuracy of output as well as the improved quality of research.