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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...

The effects of climate change including warming on nitrogen (N) availability and growth of Pinus merkusii in central Vietnam were investigated using the relationship between climate variables (rain...

The purpose of this study is to evaluate the efficacy of simple aspiration of cystic thyroid nodules by comparing with control groups to exclude the occurrence of spontaneous regression by the definition of current guidelines of American Thyroid Association.217 nodules from 210 patients with cystic thyroid nodules (cystic portion50%) were included. Nodules were classified into three groups as follows: Group 1, observation only; Group 2, fine needle aspiration (FNA) without aspiration of internal fluid; and Group 3, FNA after aspiration of internal fluid. Significant nodule size change was defined as a difference in the largest diameter of 20%, as seen on the last follow-up ultrasound (US) compared to the initial US.Demographic characteristics did not show significant differences among the three groups except for the patient age (p = 0.039). Mean nodule size significantly decreased only in group 3 (p = 0.005). Significant nodule size reductions were observed in 22.0% (13/59) in group 1, 25.7% (28/109) in group 2, and 40.8% (20/49) in group 3, respectively.Aspiration of internal fluid should be considered as the first-line procedure for both the diagnosis and treatment of cystic or predominantly cystic thyroid nodules.

Sand mixing effects on chloroform fumigation–extraction (CFE) efficiency in the determination of soil microbial biomass carbon (MBC) of water-saturated soils were investigated in two soils with different soil organic C (SOC) contents. Sand mixing increased (P < 0.001) MBC by up to 20% and 107% for the soil with low and high SOC values, respectively, suggesting that the creation of water-empty macropores by sand mixing improved chloroform fumigation efficiency. This study demonstrates that sand mixing is a feasible measure to improve CFE efficiency for the determination of the MBC of water-saturated soils, particularly for soils with a high SOC.

Canada bluejoint grass [Calamagrostis canadensis (Michx.) P. Beauv., hereafter referred to as bluejoint] outcompetes overstory tree species such as white spruce [Picea glauca (Moench) Voss] by creating a thick litter layer and competing for the available nitrogen (N). This study was conducted to investigate the effects of bluejoint litter layer (with or without litter removal) and N fertilization on soil water and N availabilities using principal component analysis (PCA) and foliar δ15N and δ13C of bluejoint in a plantation in north-central Alberta, Canada. PCA using soil properties and understory growth data demonstrated that N fertilization was more effective in changing the soil environment and resource availabilities for bluejoint growth than litter layer removal. The increase in soil N availability by N fertilization was linked with increased bluejoint foliar δ15N (by around 3‰) in fertilized plots, as a result of greater N isotopic fractionation in the fertilized plots. The more negative δ13...

Annual tree rings of Pinus densiflora, Quercus variabilis, Larix leptolepis, and Cryptomeria japonica were analyzed to examine the correlations of annual ring growth of these species with environmental variables. In all four species, annual ring area was increased over time and affected by integration of climate changes and atmospheric pollutants in the forest ecosystem. C. japonica ring growth was larger than that of other species. The annual growth rings of P. densiflora and C. japonica increased with increasing temperature (p < 0.05). The significant impacts of NO2 concentration on annual ring growth of C. japonica (p < 0.05) might reflect the nitrogen deposition. The relation of CO2 concentration with annual ring growth of C. japonica (p < 0.001) could suggest that annual ring growth of C. japonica decreased with increasing CO2 concentration, probably due to stomatal closure. The effects of SO2 concentration on annual ring area of P. densiflora, L. leptolepis, and C. japonica (p < 0.05) along with the...

Methane (CH4) emission from flooded rice fields was measured hourly over 24 h for rice (Oryza sativa L.) seasons in 2008 and 2009. The objectives of this study were to identify typical diel variation in CH4 emission and to estimate the best time of day for optimum extrapolation of daily CH4 emission. Our results showed distinct diel variation in CH4 emission, which exhibited a maximum at 14:00–15:00 and a minimum at midnight. About 5.2–5.6% of total CH4 emitted per day (110–160 mg CH4 m−2 d−1) was released at 14:00–15:00. The diel pattern of CH4 emission resembled that of air temperature (Ta). The Ta coupled with solar radiation could cause a difference in partial pressure of CH4 (DPPC) through the gas conduit of the plant. The best extrapolation of daily CH4 emission was achieved with data observed at 10:00–11:00. We concluded that DPPC-induced CH4 emission is an important mechanism causing diel variation. Present address of Seok-In Yun, Department of Bio-Environmental Chemistry, Wonkwang University, 460...

This study was conducted to determine the effect of thinning on the ecosystem respiration in a red pine forest in southern Korea. We measured the ecosystem respiration and its component respirations from soil, stem, leaf, and coarse woody debris (CWD) in thinned and control stands during 2010. The forest was thinned in October 2009. The total respiration was 8.37 and 8.82 Mg C ha−1 year−1 in the thinned and control stands, respectively. Estimated annual soil, leaf, stem, and CWD respirations in the thinned stand were 5.55, 1.41, 0.90, and 0.51 Mg C ha−1 year−1, accounting for 66, 17, 11, and 6%, respectively. Estimated annual soil, leaf, and stem respirations in the control stand were 5.54, 2.09, and 1.19 Mg C ha−1 year−1, accounting for 63, 24, and 13%, respectively. The organic C storage in tree biomass (149.24 vs. 198.61 Mg C ha−1), input from litterfall (6.79 vs. 7.92 Mg dw ha−1 year−1) and total tree biomass increment (7.67 vs. 9.28 Mg C ha−1 year−1) were all significantly lower (P

Tree rings are datable archives of environmental changes such as atmospheric pollution as tree annual growth rings store information on the growth conditions in the year of specific ring formation. Particularly, the C isotope ratio (13C/12C, expressed as δ13C) is susceptible to atmospheric CO2 and other pollutants (SO2, NOx, O3, and acid rain). Because current increases in atmospheric CO2 concentration are due to 13C-depleted CO2 emission from soil organic carbon decomposition and fossil fuel combustion, annual rings of trees grown without other pollutants may show a decreasing δ13C pattern since the industrial revolution. Meanwhile, trees exposed to atmospheric pollution (e.g. in metropolitan or industrial areas) may show increases in δ13C during the exposure period as atmospheric pollutants tend to decrease C isotope discrimination via reduced stomatal conductance or enhanced carboxylation particularly at low levels of pollutants, leading to less negative δ13C. However, as tree ring δ13C is susceptible ...

A column leaching experiment using three soils (Inceptisol, Ultisol, and Andisol) and seven livestock manure composts that had different characteristics was conducted for 19 weeks to investigate the interactive effects of composts and soils on the phosphorus (P) leaching potential of compost-amended soils and to identify the principal variables that affect P leaching. Cumulative total P leaching (TPcum) tended to increase with increasing total and available P concentration in the soils. Among various compost properties, total P concentration was positively correlated with TPcum from the compost-amended soils, except for the Andisol, which has a high P-sorption capacity. There was no significant relationship between TPcum and water-extractable P concentration of the composts, suggesting that total P rather than inorganic P concentration of composts may be successfully used in predicting P leaching potential from compost-amended soils except for soils that have a high P-sorption capacity, as in Andisol.

A laboratory incubation was conducted to evaluate nitrous oxide (N2O) production during nitrification and the effect of a nitrification inhibitor on N2O production from different profiles in a Japanese orchard Andosol. Soils were collected from five profiles: A1, A2, Bw1, Bw2, and BC. The soils were treated with ammonium sulfate at the rate of 200 mg N kg−1 with or without dicyandiamide (DCD) and incubated under aerobic conditions for 32 days. The net nitrification rate without DCD during the first 8 days was greater in the surface soils than in the subsurface soils. Accordingly, the surface soils showed a greater cumulative N2O production than the subsurface soils. Application of DCD significantly reduced the nitrification rate and thus N2O production from any depths of soils by 33.8 to 62.9%. Our study showed that substantial N2O was produced from the subsurface soil, although the amount was less than from the surface soils.

Hydrocarbon-contaminated wastes generated from oil and gas drilling activities may be used as a soil amendment once composted and further decomposition of residual hydrocarbons can be accomplished after the composts are applied to soils. To test if N fertilization may enhance hydrocarbon decomposition, we investigated the effects of N application on hydrocarbon degradation in different-aged composts (1-, 2-, 3-, and 4-year-old composts, coded as 1Y, 2Y, 3Y, and 4Y composts, respectively) through a pot experiment planted with white spruce (Picea glauca [Moench] Voss) seedlings. The percentage degradation of total petroleum hydrocarbon (TPH, C11 to C40) in the composts without N fertilization was correlated to initial NH4+ concentrations (R = 0.99, P0.001). The percentage degradation of TPH was highest in the 3Y compost (41.1%) that had an initial level of 325.3 mg NH4+ -N kg(-1) and the lowest in the IY compost (9.3%) that had an initial level of 8.3 mg NH4+ -N kg(-1). The degradation of TPH was enhanced by Nfertilization in the 1Y (from 9.3 to 15.3%) and 4Y composts (from 14.3 to 22.6%) that had low initial NH4+ concentrations. Our results show that application of NH4+ -based fertilizers may enhance the degradation of TPH when initial NH4+ concentrations in the compost are low.

Nitrogen (N) concentrations and stable N isotope abundances (δ15N) of common reed (Phragmites australis) planted in a constructed wetland were measured periodically between July 2001 and May 2002 to examine their seasonal variations in relation to N uptake and N translocation within common reed. Nitrogen concentrations in P. australis shoots were higher in the growing stage (7.5 to 24.8 g N kg−1) than in the senescence stage (4.2 to 6.8 g N kg−1), indicating N translocation from shoots to rhizomes. Meanwhile, the corresponding δ15N values were higher in the senescence stage (+12.2 to +22.4‰) than in the growing stage (+5.1 to +11.3‰). Coupled with the negative correlation (R2=0.24, P