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In intensive agricultural watersheds, riverine particulate organic matter (POM) may be transported from many sources such as rice paddies, crop uplands, forests, and livestock farming areas during rainy seasons. However, the impacts of land-use and rainfall changes on the POM sources are not well understood. In this study, changes in the sources of riverine POM were investigated in an agricultural area of Korea between 2014 and 2020/21. During this period, land-use and rainfall patterns changed dramatically. The δ

Rice residue including root and straw are unique carbon (C) source in paddy soils. However, the potential changes in quantity and chemical composition of rice residue under co-elevated atmospheric CO2 concentration ([CO2]) and air temperature (Tair) and the legacy effect of the changed chemical composition on residue decomposition have not been investigated. This study was conducted to investigate biomass, chemical composition, and decomposability of rice root and straw produced under elevated [CO2] and Tair. Root and straw biomass increased by elevated [CO2] and elevated Tair, respectively, and the greatest biomass was achieved under co-elevated [CO2]-Tair for both root and straw. The concentration of lignin (recalcitrant) decreased while that of nonstructural carbohydrates (less recalcitrant) increased by co-elevated [CO2]-Tair. The ratio of lignin-to-nitrogen (lignin/N) decreased by co-elevated [CO2]-Tair compared to ambient [CO2]-Tair due to increased N and decreased lignin concentrations. Decomposability of root (lignin/N, 36.4) produced under co-elevated [CO2]-Tair was greater than that under ambient co-elevated [CO2]-Tair (lignin/N, 53.7); however, there was no difference in decomposability for straw, which had relatively narrow range of lignin/N (27.3–36.5) regardless of [CO2]-Tair conditions. The results of this study provide a novel insight into the changes in quantity and quality of rice residue under elevated [CO2]-Tair that are necessary to predict changes in paddy soil C sequestration under global warming.

The properties of secondary salt-affected soils developed from improper irrigation and drainage management and their effects on rice growth and yield are well documented. However, relevant informat...

Forest decline due to atmospheric pollution is a consequence of long-term chronic exposure, and thus chemical proxies that are sensitive to the pollution are helpful in estimating the impact of atmospheric pollution on forest health. In this study, we explored changes in the isotopic and elemental compositions of needles of red pine (Pinus densiflora) with varying precipitation pH and concentrations of NO2 and SO2 across 18 cities to identify isotopic and chemical signatures that are sensitive to acid deposition. The cities had different intensity of traffic and industrial activities, and thus were expected to have varying levels of atmospheric pollution. The pine needles were analyzed for carbon (δ13C) and nitrogen (δ15N) isotope ratios, N concentrations, C-to-N ratio (C/N), and calcium-to-aluminum ratio (Ca/Al). Analysis of variance, simple linear correlation, and redundancy analysis were used to investigate the variations in foliar chemistry with atmospheric variables. Neither NO2 nor SO2 concentration was correlated with foliar δ13C, δ15N, N concentration, and C/N; whereas precipitation pH was correlated with the foliar parameters, suggesting that foliar chemistry is more sensitive to total acidifying materials than to individual pollutant. The foliar δ13C decreased with lowered precipitation pH, reflecting the increased 13C-depleted CO2 that was co-emitted with acidifying materials from fossil fuel combustion. Foliar δ15N decreased and foliar N concentration increased with lowered precipitation pH, indicating tree uptake of 15N-depleted N from acid deposition. Accordingly, the C/N ratio also decreased with lowered precipitation pH. However, there was no relationship between foliar Ca/Al and precipitation pH; rather. Our result suggests that δ13C, δ15N, N concentration, and C/N of pine needle samples are associated with the level of precipitation pH and thus pine needles could be used as bio-indicators of the impacts of total acidifying pollutants on forest.

Elevated atmospheric CO2 concentration ([CO2]) may change litter chemistry which affects litter decomposability. This study investigated respiration and microbial biomass of soils amended with litter of Pinus densiflora (a coniferous species; pine) and Quercus variabilis (a deciduous species; oak) that were grown under different atmospheric [CO2] and thus had different chemistry. Elevated [CO2] increased lignin/N through increased lignin concentration and decreased N concentration. The CO2 emission from the soils amended with litter produced under the same [CO2] regime was greater for oak than pine litter, confirming that broadleaf litter with lower lignin decomposes faster than needle leaf litter. Within each species, however, soils amended with high lignin/N litter grown under elevated [CO2] emitted more CO2 than those with low lignin/N litter grown under ambient [CO2]. Such contrasting effects of lignin/N on inter- and intra-species variations in litter decomposition should be ascribed to the effects of other litter chemistry variables including nonstructural carbohydrate, calcium and manganese as well as inhibitory effect of N on lignin decomposition. The microbial biomass was also higher in the soils amended with high lignin/N litter than those with low lignin/N litter probably due to low substrate use efficiency of lignin by microbes. Our study suggests that elevated [CO2] increases lignin/N for both species, but increased lignin/N does not always reduce soil respiration and microbial biomass. Further study investigating a variety of tree species is required for more comprehensive understanding of inter- and intra-species variations of litter decomposition under elevated [CO2].

Despite the ability of fly ash (FA) to remove phosphorus (P) from water via sorption and precipitation, its use as a bedding material for planted floats has never been evaluated. This study was conducted to investigate the effects of FA on P removal and chlorophyll-a (an indicator of algal growth) reduction in P-contaminated water. Six different FA rates (0, 2.5, 5, 10, 25, and 50 w/w%; codes are FA0, FA2.5, FA5, FA10, FA25, and FA50, respectively) and two rice (Oryza sativa L.) treatments (unplanted and planted) were investigated. The floats containing FA were placed on P-enriched (4 mg P L−1) baths. Water samples were collected periodically and analyzed for the concentrations of total P (TP), soluble P (SP), and chlorophyll-a. Both SP and TP decreased (P

Waterlogged paddy and water-unsaturated upland ecosystems have contrasting soil nitrogen (N) processes that affect the natural 15N abundance (15N/14N, expressed as δ15N) in different N pools. In this study, we investigated the δ15N patterns in soil and plant N pools of paddy and upland ecosystems. Samples were collected from 20 each of paddy and upland fields at the active growing season and analyzed for N concentration and δ15N. The higher (P

Understanding Spatial Variations of Water Quality Using Agricultural Nutrient Indices in Chonnam Province Byeong-Jun Jeon, Sang-Sun Lim, Kwang-Seung Lee, Se-In Lee, Jong-Hyun Ham, Sun-Ho Yoo, Kwang-Sik Yoon and Woo-Jung Choi (Department of Rural & Biosystems Engineering, Chonnam National University, Gwangju 500-757, Korea, Department of Agricultural Biotechnology, Seoul National University, Seoul 151-921, Korea)

Only limited information is available in the research area on the effect of elevated CO2 concentration ([CO2]) and air temperature (Tair) on the fertilizer N uptake by rice. This study was conducted to investigate changes in rice uptake of N derived from fertilizer (NDFF) and soil (NDFS) as well as fertilizer N uptake efficiency (FUE) with elevated [CO2] and Tair in two soils with different fertility. Rice (Oryza sativa L.) plants were grown with 15N-urea for two growing seasons (2007 in the less fertile and 2008 in the more fertile soil) in temperature gradient chambers under two (ambient and elevated) levels of [CO2] and Tair regimes. At harvest, dry matter (DM) and N uptake amount of rice compartments (root, shoot, and grain) were determined. The DM of whole rice increased (P

Soil acidification is known to be one of the constraints of tree growth; however, it is unclear how it affects tree growth at photosynthesis level (i.e., through affecting stomatal conductance vs. carboxylation rate) during the growth of trees. This paper studied the effects of soil acidification on Pinus densiflora foliar chemistry and tree ring C isotope ratio (13C/12C, expressed as δ13C) and their relationship with tree growth. Tree growth (diameter, annual growth ring area, and root biomass), soil chemistry (pH, mineral N, and exchangeable Ca and Al), foliage chemistry (N, Ca/Al, and δ13C), and tree ring δ13C in P. densiflora stands along a soil pH gradient (from 4.38 to 4.83, n = 9) in southern Korea were investigated. Overall, trees with relatively poor growth under more acidic soil conditions (low pH and Ca/Al) had lower values of foliar N concentration and δ13C and tree ring δ13C, suggesting that restricted N uptake under more acidic soil conditions caused N limitation for photosynthesis, leading to poor tree growth. In addition, relationships between mean annual area increment and carbon isotope discrimination of tree rings at five-yr intervals from 1968 to 2007 revealed that the impact of soil acidification on tree growth became severer during the last 15 yrs as negative correlations between them became significant after 1993. Reduced N uptake under acidic soil conditions resulted in lower radial growth of P. densiflora via non-stomatal limitation of photosynthesis.

BACKGROUND: Soil acidification, which is known to be one of the reasons of forest decline, is associated with decreases in exchangeable Ca and increases in Al concentration, leading to low Ca/Al ratio in soil solution. As tree rings are datable archives of environmental changes, Ca/Al ratios of annual growth ring may show decreasing pattern in accordance with the progress of soil acidification. This study was conducted to investigate Ca/Al pattern of Pinus densiflora tree ring in an attempt to test its usefulness as an indicator of historical soil acidification. METHODS AND RESULTS: Three P. densiflora tree disks were collected from P. densiflora forests in Jeonnam province, and soil samples (0-10, 10-20, and 20-30 cm in depth) were also collected from the tree locations. Soils were analyzed for pH and exchangeable Ca and Al concentrations, and Ca/Al was calculated. Annual growth rings formed between 1969 and 2007 were separated and analyzed for Ca/Al. Soil Ca/Al was positively (P

BACKGROUND: Application of urea may increase CO2 emission from soils due both to CO2 generation from urea hydrolysis and fertilizer-induced decomposition of soil organic carbon (SOC). The objective of this study was to investigate the effects of increasing urea application on CO2 emission from soil and mineralization kinetics of indigenous SOC. METHODS AND RESULTS: Emission of CO2 from a soil amended with four different rates (0, 175, 350, and 700 mg N/kg soil) of urea was investigated in a laboratory incubation experiment for 110 days. Cumulative CO2 emission (Ccum) was linearly increased with urea application rate due primarily to the contribution of urea-C through hydrolysis to total CO2 emission. First-order kinetics parameters (C0, mineralizable SOC pool size; k, mineralization rate) became greater with increasing urea application rate; C0 increased from 665.1 to 780.3 mg C/kg and k from 0.024 to 0.069 day -1 , determinately showing fertilizer-induced SOC mineralization. The relationship of C0 (non-linear) and k (linear) with urea-N application rate revealed different responses of C0 and k to increasing rate of fertilizer N. CONCLUSION(s): The relationship of mineralizable SOC pool size and mineralization rate with urea-N application rate suggested that increasing N fertilization may accelerate decomposition of readily decomposable SOC; however, it may not always stimulate decomposition of non-readily decomposable SOC that is protected from microbial

The present investigation was conducted to evaluate the regulation of sleep architecture by the red ginseng water extract (RGE) in acutely and chronically restraint stressed rats. Adult rats were fitted with sleep-wake recording electrodes. Following post-surgical recovery, rats were extensively habituated for freely moving polygraphic recording conditions. Polygraphic signs of sleep-wake activities were recorded for 24 h after RGE administration and induction of stress and were analyzed to understand the regulation of sleep architecture. Acute stress decreased wakefulness and increased total sleep, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep in both the daytime and nighttime recording. RGE shortened the daytime NREM and REM sleep, without changing the wakefulness and total sleep. RGE increased nighttime wakefulness, and decreased total, NREM and REM sleep. Chronic stress increased wakefulness and decreased total sleep in the daytime recording, and increased REM and decreased NREM sleep in both the day and night time recording. RGE ameliorated chronic stress and induced alterations of REM and NREM sleep in the day and night time sleep architecture. Acute and chronic stress could also induce alternations in cortex electroencephalogram (EEG) recording during NREM, REM sleep and wakefulness. These findings suggest that RGE may modulate the sleep behavior in acutely and chronically stressed rats and the ameliorating effect of RGE on the sleep architecture may involve in modulation of α-, θ- and δ- wave activities of the cortical EEG.

Lipid-soluble ginseng extract was prepared by n-hexane extraction of red ginseng. BALB/c-nu mice were inoculated with human lung cancer (NCI-H460) cells to establish a human tumor xenograft model in nude mice, and the lipid-soluble ginseng extract was orally administered. The tumor inhibitory rates of the lipid-soluble ginseng extract at doses of 0.1, 0.3, and 1.0 g/kg/day were 18.9% (P