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Objectives: To identify preoperative breast MR imaging and clinicopathological variables related to recurrence and develop a risk prediction model for recurrence in young women with breast cancer treated with upfront surgery. Methods: This retrospective study analyzed 438 consecutive women with breast cancer aged 35 years or younger between January 2007 and December 2016. Breast MR images before surgery were independently reviewed by breast radiologists blinded to patient outcomes. The clinicopathological data including patient demographics, clinical features, and tumor characteristics were reviewed. Univariate and multivariate logistic regression analyses were used to identify the independent factors associated with recurrence. The risk prediction model for recurrence was developed, and the discrimination and calibration abilities were assessed. Results: Of 438 patients, 95 (21.7%) developed recurrence after a median follow-up of 65 months. Tumor size at MR imaging (HR = 1.158, p = 0.006), multifocal or multicentric disease (HR = 1.676, p = 0.017), and peritumoral edema on T2WI (HR = 2.166, p = 0.001) were identified as independent predictors of recurrence, while adjuvant endocrine therapy (HR = 0.624, p = 0.035) was inversely associated with recurrence. The prediction model showed good discrimination ability in predicting 5-year recurrence (C index, 0.707 in the development cohort; 0.686 in the validation cohort) and overall recurrence (C index, 0.699 in the development cohort; 0.678 in the validation cohort). The calibration plot demonstrated an excellent correlation (concordance correlation coefficient, 0.903). Conclusion: A prediction model based on breast MR imaging and clinicopathological features showed good discrimination to predict recurrence in young women with breast cancer treated with upfront surgery, which could contribute to individualized risk stratification. Clinical relevance statement: Our prediction model, incorporating preoperative breast MR imaging and clinicopathological features, predicts recurrence in young women with breast cancer undergoing upfront surgery, facilitating personalized risk stratification and informing tailored management strategies. Key Points: Younger women with breast cancer have worse outcomes than those diagnosed at more typical ages. The described prediction model showed good discrimination performance in predicting 5-year and overall recurrence. Incorporating better risk stratification tools in this population may help improve outcomes. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the use of a commercial artificial intelligence (AI)–based mammography analysis software for improving the interpretations of breast ultrasound (US)-detected lesions. Methods: A retrospective analysis was performed on 1109 breasts that underwent both mammography and US-guided breast biopsy. The AI software processed mammograms and provided an AI score ranging from 0 to 100 for each breast, indicating the likelihood of malignancy. The performance of the AI score in differentiating mammograms with benign outcomes from those revealing cancers following US-guided breast biopsy was evaluated. In addition, prediction models for benign outcomes were constructed based on clinical and imaging characteristics with and without AI scores, using logistic regression analysis. Results: The AI software had an area under the receiver operating characteristics curve (AUROC) of 0.79 (95% CI, 0.79–0.82) in differentiating between benign and cancer cases. The prediction models that did not include AI scores (non-AI model), only used AI scores (AI-only model), and included AI scores (integrated model) had AUROCs of 0.79 (95% CI, 0.75–0.83), 0.78 (95% CI, 0.74–0.82), and 0.85 (95% CI, 0.81–0.88) in the development cohort, and 0.75 (95% CI, 0.68–0.81), 0.82 (95% CI, 0.76–0.88), and 0.84 (95% CI, 0.79–0.90) in the validation cohort, respectively. The integrated model outperformed the non-AI model in the development and validation cohorts (p < 0.001 for both). Conclusion: The commercial AI-based mammography analysis software could be a valuable adjunct to clinical decision-making for managing US-detected breast lesions. Clinical relevance statement: The commercial AI-based mammography analysis software could potentially reduce unnecessary biopsies and improve patient outcomes. Key Points: • Breast US has high rates of false-positive interpretations. • A commercial AI-based mammography analysis software could distinguish mammograms having benign outcomes from those revealing cancers after US-guided breast biopsy. • A commercial AI-based mammography analysis software may improve interpretations for breast US-detected lesions. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa L.) residues (root and straw) are unique substrates for microbes in paddy soils. Microbial respiration (RH) of paddy soils is likely to be affected by substrate quality. However, no relevant study on the effects of changed rice residue chemistry by climate change on the temperature sensitivity (Q10) of the RH of soils amended with the residues is available. To fill this knowledge gap, we conducted an incubation experiment (at 15, 25, and 35 °C) with rice residues of which lignin, nonstructural carbohydrate (NSC), and carbon-to-nitrogen ratio (C/N) were modified by growing the rice plants under different CO2 and air temperature (Tair). Co-elevated CO2 and Tair decreased lignin and C/N but increased the NSC contents of the residues, leading to the greater RH in the soils amended with rice residues produced under co-elevated CO2 and Tair compared to other CO2 or Tair treatments. However, the Q10 values of the RH of soils amended with rice residues produced under different CO2 and Tair were marginally changed, probably due to other confounding factors such as soil enzyme activity and nutrient availability. Despite that, there was a negative relationship between NSC and Q10 for soils amended with straw of which C/N is lower than root, agreeing with the kinetic theory on "substrate quality–Q10 relationship". Our result suggests that residue chemistry may not affect the Q10 of soils with root residue, but for straw-amended soils, less-recalcitrant NSC rather than more-recalcitrant lignin of straw may be critical in determining the Q10 of the soils. [ABSTRACT FROM AUTHOR]

Purpose: It is unclear whether a higher biochar (BC) application rate enhances rice (Oryza sativa L.) yield and reduces CH4 emissions. This study investigated changes in rice yield and CH4 emissions with varying BC application rates. Methods: Data on rice yield and CH4 emission from paddies amended with or without BC were collected from the literature, and the biochar effects were analyzed using the data set. Results: Across the biochar application rate from 2 to 48 t ha-1, the rice yield increased (by 10.8%) while the area-scaled (by 14.4%) and yield-scaled CH4 emission (by 22.2%) decreased. However, the correlation of BC application rates with rice yield and CH4 mitigation was not significant, implying that a higher BC application rate did not enhance rice yield and CH4 reduction. Interestingly, for a data set showing increased rice yield and decreased CH4 emission by BC, the magnitude of change in the rice yield and CH4 mitigation per unit weight of BC (1 t ha-1) decreased with an increase in the BC application rate. These results suggest that BC effects on rice yield and CH4 mitigation are not additive, probably because of the decreases in the inherent capacity of unit weight of BC to enhance rice yield and reduce CH4 emission, which might be caused by the adverse effects of toxic compounds contained in BC, losses of BC, and a higher degree of nutrient immobilization by BC. Conclusions: Annual BC application at a low rate (e.g., 2 t ha-1) rather than a luxury application may be an effective and economical strategy for long-term rice yield enhancement and CH4 mitigation using BC. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the improvement of mammography interpretation for novice and experienced radiologists assisted by two commercial AI software. Methods: We compared the performance of two AI software (AI-1 and AI-2) in two experienced and two novice readers for 200 mammographic examinations (80 cancer cases). Two reading sessions were conducted within 4 weeks. The readers rated the likelihood of malignancy (range, 1–7) and the percentage probability of malignancy (range, 0–100%), with and without AI assistance. Differences in AUROC, sensitivity, and specificity were analyzed. Results: Mean AUROC increased in both novice (0.86 to 0.90 with AI-1 [p = 0.005]; 0.91 with AI-2 [p < 0.001]) and experienced readers (0.87 to 0.92 with AI-1 [p < 0.001]; 0.90 with AI-2 [p = 0.004]). Sensitivities increased from 81.3 to 88.8% with AI-1 (p = 0.027) and to 91.3% with AI-2 (p = 0.005) in novice readers, and from 81.9 to 90.6% with AI-1 (p = 0.001) and to 87.5% with AI-2 (p = 0.016) in experienced readers. Specificity did not decrease significantly in both novice (p > 0.999, both) and experienced readers (p > 0.999 with AI-1 and 0.282 with AI-2). There was no significant difference in the performance change depending on the type of AI software (p > 0.999). Conclusion: Commercial AI software improved the diagnostic performance of both novice and experienced readers. The type of AI software used did not significantly impact performance changes. Further validation with a larger number of cases and readers is needed. Clinical relevance statement: Commercial AI software effectively aided mammography interpretation irrespective of the experience level of human readers. Key Points: • Mammography interpretation remains challenging and is subject to a wide range of interobserver variability. • In this multi-reader study, two commercial AI software improved the sensitivity of mammography interpretation by both novice and experienced readers. The type of AI software used did not significantly impact performance changes. • Commercial AI software may effectively support mammography interpretation irrespective of the experience level of human readers. [ABSTRACT FROM AUTHOR]

Purpose: Soil salinity is often measured with electrical conductivity (EC) of soil–water extracts (ECw), and thus, conversion of ECw to saturated paste EC (ECe) is required for practical uses of ECw. However, conversion factors (CF, the ratio of ECe to ECw) vary widely depending on soil properties such as soil texture and ionic composition. This study was conducted to develop a novel procedure to obtain soil-specific CF by performing random forest (RF) and multiple regression (MR) modeling using EC and soil properties. Methods: Soil samples (n = 320) were collected from paddy fields in 16 reclaimed coastal areas of South Korea in 2018–2022. The samples were analyzed for EC (EC1:5 and ECe) and other soil properties including soil particle size, organic matter content, and exchangeable sodium percentage (ESP). The most important soil properties affecting the CF ratios were explored using RF modeling, and a MR equation was developed to estimate ECe using EC1:5 and the soil properties as parameters. Results: The RF model indicated that ESP and clay content are the key soil factors affecting CF variability, contributing 56.6% and 20.0% of the variability, respectively. Therefore, a multiple regression model was developed to predict CF using ESP and clay content, CF = 7.179 − 0.084 × Clay + 1.096 × ln(ESP). The predicted ECe was linearly correlated with the measured ECe (r2 = 0.84) with a marginal error (3.1%). Conclusion: Our study provides a novel method to estimate ECe from ECw by performing RF and MR modeling using soil-specific variables such as clay content and ESP. [ABSTRACT FROM AUTHOR]

This review analyzes the data on co-variations in δ13C and δ15N of soils with land-use types, management, and disturbance obtained from literature to explore potential implications of the dual isotopes in the study of soil organic matter (SOM) sources and C and N processes. Overall, croplands (δ13C and δ15N were − 20.3 ± 4.4‰ and + 7.6 ± 4.4‰, respectively) had greater isotopic values than grasslands (‒26.3 ± 3.0‰ and + 5.4 ± 1.1‰, respectively) and forests (− 26.0 ± 1.1‰ and + 4.3 ± 2.2‰, respectively). For intensively managed lands such as croplands and grasslands, application of organic inputs such as manure and compost of which isotopic signatures differed from the indigenous SOM was the main driver of co-variations in the δ13C and δ15N of SOM. For natural forests, both δ13C and δ15N of SOM co-increased with soil depth, reflecting heavy isotope enrichment during microbial stabilization of SOM and the potential influence of 13C-depleted atmospheric CO2 and 15N-depleted N deposition on the upper soils. Such vertical co-enrichments of 13C and 15N were disturbed by a land-use conversion to other lands including croplands. Though there were indications that land management practices such as tillage in croplands and grazing in grasslands, land-use changes, and land disturbance including forest fire might also affect both δ13C and δ15N, more data need to be accumulated to find a general trend of the isotopic variations of SOM. Analysis of both δ13C and δ15N may enlarge understanding of changes in SOM sources and soil C and N cycling by land-use types, management, change, and disturbance. [ABSTRACT FROM AUTHOR]

Purpose: Physico-chemical mechanisms of soil organic carbon (SOC) protection in volcanic ash soils (Andisols) are well understood. However, this role of microbes in the process is unclear. This study was conducted to understand the microbial contribution to SOC accumulation in Andisols, in comparison with non-volcanic ash soils (Inceptisols). Methods: Soils were collected from agricultural land, coniferous forest, and deciduous forest (n = 7 per land-use for Andisol, n = 3 for Inceptisols). Soils were analyzed for SOC and physico-chemical properties related to SOC protection (clay content, aggregate size distribution, pH, and active Al and Fe concentration). Soil microbial biomass C (MBC), composition, respiration, and metabolic quotient (qCO2) were further analyzed. Results: Forest Andisols had greater SOC compared to agricultural Andisols and Inceptisols from all land-use types. The greater SOC content in forest Andisols was associated with the complexation of SOC with clay and active Al and Fe. The physico-chemical protection of SOC in forest Andisols was further related to lower percentage of total SOC respired as CO2 (% RCO2/SOC) and qCO2, which indicates that microbes assimilate more C than they respire. Microbial composition as well as the inter-correlation among qCO2, RCO2/SOC, and SOC content suggested that microbes in forest Andisols are likely to incorporate C derived from the decomposition of plant-derived C rather than indigenous SOC, contributing to SOC accumulation in the soils. Conclusions: Our study suggests that microbial contribution is critical for enhanced SOC in forest Andisols in addition to the inherent soil physico-chemical properties, but not in agricultural Andisols. [ABSTRACT FROM AUTHOR]

The temperature sensitivity (Q10) of heterotrophic soil respiration (RH) of forests affects terrestrial carbon (C) dynamics under climate change. However, the effects of changed chemistry of tree leaf litter (referred to as litter hereafter) under elevated atmospheric CO2 concentrations ([CO2]) on the Q10 of RH has not been explored. To fill the knowledge gap, the Q10 of RH was investigated through incubation experiments at three temperature levels using litters of pine (Pinus densiflora Siebold & Zucc.) and oak (Quercus variabilis Blume) that were produced under ambient ([CO2]a) and elevated ([CO2]e) [CO2]. Regardless of [CO2] conditions, pine litter had higher lignin but lower nonstructural carbohydrate (NSC), calcium (Ca), and manganese (Mn) concentrations than oak, suggesting that pine litter has inherently poor chemistry. [CO2]e increased the ratios of lignin-to-nitrogen (lignin/N; by 58 and 122% for pine and oak, respectively) and C-to-N (C/N; by 47 and 125%, respectively) of litter through decreasing litter N concentration. For soils amended with [CO2]a-litter, Q10 was greater for pine (1.54) than oak (1.39) litters in agreement with the kinetic theory on the substrate quality-Q10 relationship. However, amending [CO2]e-litter decreased Q10 for pine (1.44) but marginally increased Q10 for oak (1.44). The decreased Q10 for pine by [CO2]e could be attributed to the inherently poor litter chemistry (e.g., high lignin, and low NSC, Ca, and Mn concentrations). Our study shows that the changed litter chemistry by [CO2]e modifies Q10 of RH of litter-amended soils. [ABSTRACT FROM AUTHOR]

Purpose: This study was conducted to investigate variations in the stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) of agricultural soils under different land uses (i.e., paddy, upland, and orchard) that subjected to different fertilization management (i.e., 15 N-depleted synthetic fertilizer and 13C- and 15 N-enriched livestock manure and compost application). Materials and methods: Soil samples were collected from paddy, upland, and orchard fields in an intensive agricultural area, and forest (pine and oak) soils were additionally included as background soils. The C and N concentrations and isotope ratios of both bulk and water-extractable soil fractions were analyzed. Results and discussion: The δ13C and δ15N of agricultural soils were higher than those of forest soils, reflecting repeated manure and compost applications (for both δ13C and δ15N) and higher N loss (for δ15N) in agricultural soils. Among agricultural soils, orchard (− 24.2‰ for δ13C and + 10.6‰ for δ15N) and upland (− 25.4‰ and + 9.6‰, respectively) soils which received higher rates of manure and compost were more enriched with 13C and 15N compared with paddy (− 28.0‰ and + 4.9‰, respectively). Such differences in the isotopic compositions among agricultural soils were also found for water-extractable soil fractions. Conclusions: Our study suggests that δ13C and δ15N of agricultural soils are affected by land use types with different fertilization management, particularly application of 13C- and 15 N-enriched livestock manure and compost. The δ13C and δ15N could be used as chemical indicators to evaluate the effects of the application of manure and compost on soil C and N dynamics. [ABSTRACT FROM AUTHOR]

Objectives: To prospectively evaluate the diagnostic performance of screening ABUS as the primary screening test for breast cancer among Korean women aged 40–49 years. Methods: This prospective, multicenter study included asymptomatic Korean women aged 40–49 years from three academic centers between February 2017 and October 2019. Each participant underwent ABUS without mammography, and the ABUS images were interpreted at each hospital with double-reading by two breast radiologists. Biopsy and at least 1 year of follow-up was considered the reference standard. Diagnostic performance of ABUS screening and subgroup analyses according to patient and tumor characteristics were evaluated. Results: Reference standard data were available for 959 women. The recall rate was 9.8% (95% confidence interval [CI]: 7.9%, 11.7%; 94 of 959 women) and the cancer detection yield was 5.2 per 1000 women (95% CI: −0.6, 11.1; 5 of 959 women). There was only one interval cancer. The sensitivity was 83.3% (95% CI: 53.5%, 100%; 5 of 6 cancers) and the specificity was 90.7% (95% CI: 88.8%, 92.5%; 864 of 95. women). The positive predictive values of biopsies performed (PPV3) was 20.0% (95% CI: 4.3%, 35.7%; 5 of 25 women). Women with heterogeneous background echotexture had a higher recall rate (p =.009) and lower specificity (p =.036). Women with body mass index values < 25 kg/m2 had a higher mean recall rate (p =.046). Conclusion: In East Asia, screening automated breast US may be an alternative to screening mammography for detecting breast cancers in women aged 40–49 years. Key Points: • Automated breast US screening for breast cancer in asymptomatic women aged 40–49 is effective with 5.2 per 1000 cancer detection yield. • Women with heterogeneous background echotexture had a higher recall rate and lower specificity. • Women with body mass index < 25 kg/m2had a higher recall rate. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the positive predictive values (PPVs) of calcifications with suspicious morphology by incorporating distribution and clinical factors in two separate cohorts to provide more practical guidance for management. Methods: This retrospective study included 1076 consecutive women from two cohorts (cohort A, 556; cohort B, 520), with calcifications of suspicious morphology seen on mammography that were pathologically confirmed or followed with mammography. Reader-averaged PPVs of the calcifications were analyzed and compared by logistic regression using the generalized estimating equation. Multivariate logistic regression analysis was performed to evaluate independent factors associated with the PPVs of suspicious calcifications. Results: Overall reader-averaged PPVs of suspicious calcifications were 16.8% and 15.2% in cohort A and B, respectively. Reader-averaged PPVs according to morphology in cohort A and B were as follows: amorphous 9.1%, 6.4%; coarse heterogeneous 16.1%, 22.1%; fine pleomorphic 78.8%, 44.7%; and fine linear branching 78.6%, 85.1%, respectively (p < 0.001). PPVs for diffuse amorphous combinations were 2.6% and 2.6%, and for regional amorphous calcifications, 3.6% and 3.1%, respectively. Among diffuse amorphous calcifications, the PPVs for women ≥ 50 years and women without a personal history of breast cancer ranged from 0.0 to 1.9%. Conclusions: Amorphous calcifications have lower reader-averaged PPVs compared to calcifications with other suspicious morphology, falling into the BI-RADS 4a assessment (PPV 2–10%). Amorphous calcifications with diffuse distributions detected in women > 50 years old and without a personal history of breast cancer have reader-averaged PPVs < 2.0%. Further prospective studies are necessary to confirm if these patients can be managed with imaging follow-up. Key Points: • In two cohorts, reader-averaged positive predictive values (PPVs) for suspicious calcifications showed lower rates for amorphous calcifications. • In two separate cohorts, reader-averaged PPVs showed lower rates for diffuse amorphous calcifications, falling into the BI-RADS 4a assessment category (PPV 2–10%). • Diffuse amorphous calcifications detected in women > 50 years old and without a personal history of breast cancer have reader-averaged PPVs < 2.0%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the usefulness of bilateral mammography in male patients with unilateral breast symptoms, including investigation of the diagnostic performance of unilateral and bilateral reviews and the average glandular dose (AGD) per exposure. Methods: Two hundred seventy-one consecutive male patients (mean age, 57 years) with unilateral breast symptoms underwent bilateral mammography. Image interpretation was performed in two ways, first with a unilateral review of the symptomatic breast and then with a bilateral review. A modified BI-RADS scale (from 1 to 5) was used. The diagnostic performance of unilateral and bilateral reviews was compared, and contralateral breast abnormalities and the AGD per exposure were recorded. We also analyzed ultrasound (US) results and compared them with mammography. Results: Of 271 male patients, 29 were pathologically diagnosed with breast cancer. There was no bilateral breast cancer. The sensitivity, specificity, positive and negative predictive values, and accuracy were 96.6%, 96.7%, 77.8%, 99.6%, and 96.7%, respectively, for unilateral review, and 96.6%, 95.9%, 73.7%, 99.6%, and 95.9% for bilateral review. Receiver operator characteristic analysis showed excellent diagnostic performance for both methods: the area under the curve (AUC) was 0.966 for unilateral review and 0.962 for bilateral review (p = 0.415). The mean AGD per exposure was 1.10 ± 0.29 mGy for symptomatic breast and 1.04 ± 0.30 mGy for contralateral breast (p < 0.001). Diagnostic performance parameters of US were not significantly different from bilateral or unilateral review of mammography. Conclusion: The diagnostic performance of unilateral mammography is comparable with bilateral mammography in male patients with unilateral breast symptoms. Unilateral mammography also has the advantage of reducing radiation exposure. Key Points: • There is limited knowledge about standardized guidelines or recommendations for imaging the male breast. • Unilateral mammography for male patients with unilateral breast symptoms showed comparable diagnostic performance with bilateral mammography. • Both unilateral and bilateral mammography showed excellent diagnostic performance in the assessment of male patients with unilateral breast symptoms. [ABSTRACT FROM AUTHOR]

Using the stable N isotope technique, it is possible to trace N derived from many sources and pools and thus quantify the gross N transformation rates and plant N uptake, and the processes of gaseous N emissions (Choi et al. [2]). Carbon (C) and nitrogen (N) are key elements governing soil productivity and sustainability in terrestrial ecosystems including croplands, forests, and wetlands. The synthesized and experimental data published in the articles of this issue provides novel insights into the use of stable C and N isotopes in the study of C and N dynamics in different land uses under global change. [Extracted from the article]

Objective: To investigate and compare the effect of preoperative breast magnetic resonance (MR) imaging on recurrence-free survival (RFS) and overall survival (OS) outcomes among patients with invasive lobular carcinoma (ILC).Methods: A total of 287 ILC patients between January 2005 and December 2012 were included. One hundred twenty (41.8%) had undergone preoperative breast MR imaging (MR group) and 167 (58.2%) had not (no MR group). Two groups were matched for 21 covariates in terms of patient demographics, tumor characteristics, and clinical features. We compared unmatched variables between the patients with and without breast MR imaging using the chi-square or Student's t test. Comparisons of matched data were performed with McNemar's test or test of symmetry for categorical variables and paired t test for continuous variables. The RFS and OS outcomes were compared using the Kaplan-Meier estimates. MR effects were estimated after adjusting for significant potential confounders of specific outcomes in the multivariable modeling.Results: In the matched cohort, no statistically significant association was observed between MR imaging and total recurrence (hazard ratio [HR], 1.096; p = 0.821), loco-regional recurrence (HR, 1.204; p = 0.796), contralateral breast recurrence (HR, 0.945; p = 0.952), or distant recurrence (HR, 1.020; p = 0.973). MR imaging was associated with improved OS with 51% reduction, but not significantly (HR, 0.485; p = 0.231). Analysis with multivariable Cox regression model indicated that MR imaging was not significant independent factor for better RFS (HR, 0.823; p = 0.586) or improved OS (HR, 0.478; p = 0.168).Conclusion: Preoperative MR imaging is not significant prognostic factor and produces no apparent recurrence or survival outcome benefits in ILC patients.Key Points: • Preoperative breast MR imaging in invasive lobular carcinoma was associated with a better overall survival with 51% reduction, but not statistically significant. • Preoperative breast MR imaging does not show significant prognostic value in invasive lobular carcinoma as there is no apparent benefit in terms of recurrence or survival outcomes. [ABSTRACT FROM AUTHOR]

Rice growing in paddy fields equipped with irrigation and drainage systems is less affected by unfavorable weather patterns such as prolonged dry periods and severe storms, but for the same reason, the fields discharge water to maintain suitable water depths even between rainfall events. Studies have been done to examine the quality of water drained from rice paddy fields during or after rainfall events. However, it is not clear how drainage affects the water quality of downstream waterbodies, especially during non-rainfall periods. We investigated the water quality characteristics of rainfall and non-rainfall rice paddy drainage, which was characterized by biological oxygen demand (BOD) and chemical oxygen demand (COD). In this study, hydrological variables including water inflow/outflow rates, depth, BOD, and COD were monitored at a paddy field in Korea from 2008 to 2012. This study then quantified how BOD and COD loadings are controlled by irrigation and drainage management practices. Water quality measurements showed that rainfall events that resulted in rainfall depths greater than 50 mm are responsible for half of the overall BOD and COD loads discharged by rainfall events of the fields. On the other hand, a quarter of the total BOD and COD was attributed to events that provided rainfall depths less than 10 mm. The results suggested that the BOD and COD loads of rainfall events can be reduced by up to 25% if water at paddy fields is carefully managed in small rainfall events. Water samples taken during rainfall events had greater nutrient loads only by 6 kg BOD ha−1 (17 kg BOD ha−1 vs. 11 kg BOD ha−1) and 7 kg COD ha−1 (41 kg COD ha−1 vs. 34 kg COD ha−1) compared to those of the non-rainfall periods in the cropping season. Such a finding indicates the significant impacts of paddy field drainage practices on downstream water quality between rainfall events, particularly when considering a long period of non-rainfall. The monitoring data also showed that the standard unit load of 15.5 kg BOD ha−1 established for rice paddy fields by the Ministry of Environment, the environmental authority of Korea, is substantially different from the actual BOD load, because the non-rainfall BOD loads were not considered in the standard. Thus, this study suggests that non-rainfall BOD loads should be counted and managed for successful implementations of total maximum daily load programs. [ABSTRACT FROM AUTHOR]

Purpose: Lead (Pb) sorption capacity (PbSmax) and distribution in chemical and particle-size fractions of six soils with different physico-chemical properties were investigated to explore the principal properties of soils that affect Pb sorption.Materials and methods: A series of experiments of Pb sorption and soil chemical and particle-size fractionation of sorbed Pb were conducted with six soils of different texture, mineralogy, organic matter concentration, cation exchange capacity (CEC), and Fe-Mn concentrations.Results and discussion: Soils either developed from volcanic ash or containing smectite showed relatively higher PbSmax than the other soils. Across the soils, clay content, organic matter concentration, and total Fe concentrations were significantly (p < 0.05) correlated with PbSmax. Concentrations of Pb bound with Fe-Mn and exchangeable Pb sorbed on to negatively charged sites were greater than the other chemical fractions. In the particle-size fractions, clay-sized particles had the greatest Pb concentration, suggesting that this fraction was most responsible for Pb sorption. The Pb concentration in coarse particle fractions (silt and sand) showed a positive relationship with organic matter concentration, indicating that organic matter in coarse particles was a factor determining Pb sorption. However, such relationship was not found for clay-sized particles, suggesting that complexation with organic matter was not a key mechanism for Pb sorption onto clay-sized particles.Conclusions: Our study which combined sorption and chemical and particle-size fractionation experiments suggests that complexation of Pb with Fe and Mn oxides and interaction with negatively charged sites of clay-sized particles are the key processes of Pb sorption in the studied soils. For coarse particles, it was suggested that association with organic matter is a Pb sorption mechanism. [ABSTRACT FROM AUTHOR]

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]. [ABSTRACT FROM AUTHOR]

Early establishment of seedlings in reclaimed oil sand areas is often limited by low nutrient and water availability due to factors such as strong understory vegetation competition. Management practices such as nursery fertilization and field weed control could help early establishment of planted seedlings and reclamation success. We investigated the effect of nursery nutrient loading and field weed control on the growth, nitrogen (N) retranslocation within seedling components, and plant N uptake from the soil for white spruce ( Picea glauca [Moench] Voss) seedlings planted on a highly competitive reclaimed oil sands site for two years. Exponential fertilization during nursery production increased the root biomass but not the nutrient reserve in the seedling. In the field experiment, on average across the treatments, 78 and 49% of the total N demand of new tissue growth in the first and second year were met by N retranslocation, respectively. Though exponential fertilization did not affect N retranslocation, it increased the percent height and root collar diameter growth. Weed control increased not only the growth of seedlings by increasing soil N availability, but also N retranslocation within the seedlings in the second year after outplanting. We conclude that vegetation management by weed control is feasible in improving the early growth of white spruce seedlings planted on reclaimed soils and facilitate tree establishment in the oil sands region. Optimization of the nursery exponential N fertilization regime for white spruce may further help with early revegetation of reclaimed oil sands sites. [ABSTRACT FROM AUTHOR]

Purpose: Fly ash (FA) and zeolite (Z) are known to increase nutrient retention in paddy soils through the immobilization of phosphorus (P) by FA and nitrogen (N) by Z. However, there is a possibility that the co-application of the amendments may hamper rice growth due to reduced availability of the nutrients. This study was conducted to investigate the effects of the co-application of FA and Z on soil N and P availability and rice growth. Materials and methods: Rice was cultivated in soils without the amendment (control) and with the amendment: FA alone, Z alone, and both FA and Z. Tiller number, dry matter (DM), rice uptake of N and P, and soil N and P concentrations were determined. Results and discussion: The application of FA and Z increased N and P concentrations in the soils; however, such increased nutrient retention did not translate to DM increases. Results suggested that reduced mobility of nutrients hampered tillering in the early growth period, eventually leading to a reduction in DM accumulation at the harvest. Due to the nutrient limitation caused by FA and Z, the rice grown with both FA and Z did not survive at the harvest. Conclusions: Our study shows that the application of FA and Z does not always improve rice growth due to nutrient limitation, especially in a low fertility soil. Furthermore, the co-application of FA and Z should be avoided, as the negative impact of FA or Z on nutrient limitation became more severe when FA and Z were co-amended. [ABSTRACT FROM AUTHOR]

As rice paddies are widespread sources of water pollution in the agricultural regions of the Asian monsoon area, a mechanistic understanding of nutrient loss from paddies is critical for water quality management. A 2-year experiment was conducted in a typical monsoon-affected rice field to improve our understanding of the impacts of rainfall and agricultural management practice on nitrogen (N) and phosphorus (P) loss. Samples of paddy drainage water were collected during rainfall events ( n = 25) and analyzed for total N (T-N) and total P (T-P) concentrations. The impacts of rainfall (amount, duration, and intensity) and agricultural management practice (transplanting and fertilization) on the event mean concentration (EMC) and loss of nutrient were assessed using regression analyses. The results showed that T-N and T-P concentrations were affected by agricultural practice; meanwhile, loss of T-N and T-P was correlated with rainfall characteristics. Specifically, the EMC of T-N but T-P was negatively ( p < 0.001) correlated with the number of days after agricultural practice in both years, which likely represents a decrease in nutrient availability in paddy water over time. Loss of T-N and T-P was positively ( p < 0.01) correlated with rainfall amount, and this suggests that the rainfall-runoff process is a key driver of nutrient loss in the study area. Our results suggest that rainfall amount and days after transplanting need to be taken into account when estimating nutrient loss from rice paddies in monsoon regions. [ABSTRACT FROM AUTHOR]

Waterlogged paddy and water-unsaturated upland ecosystems have contrasting soil nitrogen (N) processes that affect the natural N abundance (N/N, expressed as δN) in different N pools. In this study, we investigated the δN 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 δN. The higher ( P < 0.001) concentration (22.1 mg N kg) and lower δN (6.9 ‰) of NH in paddy than in upland soils (6.1 mg N kg and 9.2 ‰, respectively) likely reflected the lower nitrification potential in paddy soils. On the other hand, a higher ( P < 0.001) δN of NO in paddy (12.7 ‰) than in upland soils (4.7 ‰) indicated higher denitrification rates in paddy soils. The positive ( P < 0.01) correlation of the δN of soil organic N with the δN of NH rather than with that of NO suggested a tight linkage between organic N and NH as a result of immobilization-mineralization turnover of NH. Therefore, in waterlogged paddy soils where nitrification was restricted, a high rate of microbial immobilization-mineralization turnover might lead to a lower δN of soil N (total N, organic N, and NH) than those for upland. The δN in plant N pools also reflected the dominant mineral N species in paddy (NH) and upland soils (NO). We conclude that contrasting soil N processes (particularly nitrification) leave distinct δN signatures in the soil and plant N pools between paddy and upland fields. [ABSTRACT FROM AUTHOR]

Background and aims: Understanding changes in soil N cycling with stand development is critical for forest management as tree growth is affected by soil N availability. The aim of this study was to evaluate the changes in soil N availability and loss with stand development in trembling aspen ( Populus tremuloides Michx.) and jack pine ( Pinus banksiana Lamb.) in northeastern Alberta, Canada. Methods: Soil inorganic N availability (measured as N supply rate) and foliar N chemistry (N concentration and δN) in trembling aspen stands ranged from 52 to 70 years old ( n = 7) and jack pine stands 43 to 78 years old ( n = 8) were investigated in 2008 and 2009. The relationships among the ratios of NO-N to total inorganic N (NO-N/TIN), foliar N concentration, and foliar δN with stand age were also explored by regression analyses. Results: Total inorganic N supply rates did not systematically change with stand age across stand types, soil layers and measurement periods; whereas NO-N/TIN showed a decreasing tendency with stand age, suggesting that nitrification and associated N loss potential became smaller in older stands with greater limitation in soil N availability. Foliar δN decreased with stand age from −1.7 to −4.7‰ for aspen and from −4.1 to −7.1‰ for jack pine, and there were positive correlations between foliar δN and soil NO-N/TIN, suggesting that decreased soil N loss led to less N-depletion in the inorganic N available for tree uptake in older stands. However, foliar N concentration did not significantly change with stand age, suggesting that there were other N sources such as organic N in the forest floor, in addition to the inorganic N, available for plant uptake. Conclusions: Our results suggest that soil inorganic N availability became more limited as stand age increased. In addition, the ratio of NO-N/TIN and its relationship with foliar δN indicated decreased soil N loss potential and shifted N sources with stand age in boreal forests that are typically N-limited. Our study demonstrated that declining nitrification with increasing stand age might be one of the mechanisms mediating N-limitation in the studied boreal forests. [ABSTRACT FROM AUTHOR]

Background and aims: Only limited information is available in the research area on the effect of elevated CO concentration ([CO]) and air temperature (T) 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 [CO] and T in two soils with different fertility. Methods: Rice ( Oryza sativa L.) plants were grown with N-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 [CO] and T regimes. At harvest, dry matter (DM) and N uptake amount of rice compartments (root, shoot, and grain) were determined. Results: The DM of whole rice increased ( P < 0.01) with co-elevation of [CO] and T in both years (by 28.0 % in 2007 and by 27.4 % in 2008). The DM in 2008 was greater than that in 2007 by 48.1 to 63.1 % probably due to better soil fertility as well as longer sunshine hours (456 h vs. 568 h). Co-elevation of [CO] and T increased total N uptake, NDFF, and NDFS by 19.4 to 29.1 % in general compared to the ambient conditions. The FUE increased with co-elevation of [CO] and T from 46.5 to 59.5 % in 2007 and from 36.7 to 43.8 % in 2008. Conclusions: The projected global warming with elevated [CO] is expected to increase FUE via enhanced DM accumulation with less increments in the soils that have higher indigenous soil N availabilities. [ABSTRACT FROM AUTHOR]

Conversion of synthesis gas (CO and H) to ethanol can be an alternative, promising technology to produce biofuels from renewable biomass. To distinguish microbial utilization of carbon source between fructose and synthesis gas CO and to evaluate biological production of ethanol from CO, we adopted the C-enrichment of the CO substrate and hypothesized that the residual increase in δC of the cell biomass would reflect the increased contribution of C-enriched CO. Addition of synthesis gas to live culture medium for ethanol fermentation by Clostridum ljungdahlii increased the microbial growth and ethanol production. Despite the high C-enrichment in CO (99 atom % C), however, microbial δC increased relatively small compared to the microbial growth. The uptake efficiency of CO estimated using the isotope mass balance equation was also very low: 0.0014 % for the low CO and 0.0016 % for the high CO treatment. Furthermore, the fast production of ethanol in the early stage indicated that the presence of sugar in fermentation medium would limit the utilization of CO as a carbon source by C. ljungdahlii. [ABSTRACT FROM AUTHOR]

Background and aims: 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 (C/C, expressed as δC) and their relationship with tree growth. Methods: 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 δC), and tree ring δC in P. densiflora stands along a soil pH gradient (from 4.38 to 4.83, n = 9) in southern Korea were investigated. Results: Overall, trees with relatively poor growth under more acidic soil conditions (low pH and Ca/Al) had lower values of foliar N concentration and δC and tree ring δC, 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. Conclusions: Reduced N uptake under acidic soil conditions resulted in lower radial growth of P. densiflora via non-stomatal limitation of photosynthesis. [ABSTRACT FROM AUTHOR]

Background and aims: Canada bluejoint grass is a strong competitor for water and N against young white spruce trees in regenerating boreal forests in moist habitats. We investigated foliar δC and δN responses of white spruce to understory removal and N fertilization to infer treatment effects on soil water and N dynamics. Methods: An experiment with understory removal and N fertilization as the main and split-plot treatments was conducted in a 13-year-old white spruce plantation in the boreal region for 2 years. Soil N availability, gravimetric soil moisture content, tree growth, foliar C and N concentrations, and foliar δC and δN values were determined. Results: Foliar δC was increased by understory removal in the second year and by N fertilization in the first year. There was a positive ( P < 0.01) relationship between foliar δC and N concentration, suggesting that understory removal and N fertilization improved tree growth via increased N availability and thus increased carboxylation rate of photosynthesis. The positive correlation ( P < 0.01) of foliar δN with foliar N concentration and with available soil N indicated that understory removal and N fertilization facilitated N isotope fractionation accompanying increased soil N turnover. Conclusions: Foliar δC and its relationship with other variables suggested that understory removal and N fertilization improved white spruce growth mainly through enhanced carboxylation rate due to greater N availability rather than increased stomatal conductance. Specifically, understory removal and N fertilization increased soil N availability and subsequently induced N loss from the system, leading to a higher N concentration and δN in the foliage. Control of competing vegetation and N fertilization could be used as management tools to reduce N limitation. [ABSTRACT FROM AUTHOR]

Purpose: Fly ash can reduce CO emission from soils via biochemical (i.e., inhibition of microbial activity) and physicochemical (i.e., carbonation) mechanisms. This study investigated the effects of fly ash amendment on biochemical and physicochemical reduction in CO emission from normal and saline soils. Materials and methods: The physicochemical mechanisms of reduction in CO emission by fly ash were estimated in a batch experiment with carbonate solution as a CO source by the scanning electron microscope (SEM) and inductively coupled plasma analyses. Biochemical mechanisms of reduction in CO emission by fly ash were investigated in a 3-day laboratory incubation experiment with normal and saline soils in the absence and presence of fly ash. Finally, the effects of fly ash amendment at a variety rate from 2 to 15 % ( w/ w) on CO emission from normal and saline soils in the presence of additional organic carbon source (glucose) were investigated through a 15-day laboratory incubation study. Results and discussion: In the batch experiment with carbonate solution, both the SEM image of fly ash and changes in soluble Ca and Mg concentrations during reaction with carbonate suggested that the formation of CaCO and MgCO via carbonation was the principal physicochemical mechanism of carbonate removal by fly ash. In the 3-day incubation study conducted to examine biochemical mechanisms of reduction in CO emission by fly ash, microbial respiration of saline soil was inhibited ( P < 0.05) by fly ash due to high pH, salinity, and boron concentration of fly ash; meanwhile, for normal soil, there was no inhibitory effect of fly ash on microbial respiration. In the 15-day incubation with glucose, fly ash application at a variety rates from 2 to 15 % ( w/ w) reduced CO emission by 3.6 to 21.4 % for normal and by 19.8 to 30.3 % for saline soil compared to the control without fly ash. For saline soil, the reduction in CO emission was attributed primarily to inhibition of microbial respiration by fly ash; however, for normal soil in which suppression of microbial respiration by fly ash was not apparent, carbonation was believed to play an important role in reduction of CO emission. Conclusions: Therefore, fly ash may be helpful in reducing CO emission from normal soils via carbonation. For saline soil, however, fly ash needs to be carefully considered as a soil amendment to reduce CO emission as it can inhibit soil microbial activities and thus degrade soil quality. [ABSTRACT FROM AUTHOR]

Purpose: Since substrate quality can influence the C mineralization pattern of compost in soils, proper selection of compost is important in increasing soil organic carbon (SOC) levels. This study investigated the effect of substrate quality of livestock manure composts on compost C mineralization and retention in soils. Materials and methods: A laboratory incubation experiment using four livestock manure composts (with different degrees of stability and other substrate qualities) and three soils (Inceptisol, Ultisol, and Andisol) was conducted for 100 days. Emission of CO from the compost-amended soils was periodically measured and cumulative CO emission was calculated as the percentage of total organic C (TOC) of applied compost (% C). The % C patterns were fitted with a double exponential first-order kinetics model to obtain the mineralizable C pool size and potentially retainable C in the soils. Results and discussion: The compost stability degree (SD) ranged from 31.4 to 61.5%, indicating a wide range of recalcitrance to microbial decomposition in the four composts used in our study. Among other compost quality indices, the KSO extractable organic C concentration and molar ratio of NH/NO decreased with increasing SD values. The % C ranged from 1.6 to 11.4% and decreased as SD increased, suggesting that compost C mineralization in soils can be predicted using SD. The pool size (rapid pool + slow pool) of mineralizable organic C estimated using a first-order kinetic model ranged from 1.7 to 28.5% and tended to decrease with increasing SD. Among the three soils, Andisol showed relatively low % C and mineralizable C pool size due to its inherent SOC protection mechanism via Al-organic matter complex. Conclusions: Our results suggest that application of compost with high SD and low extractable organic C would be more efficient in increasing SOC level due to a higher retention of compost C in the soils. The different patterns of C mineralization and retention among the three soils also suggest that not only compost quality but also soil characteristics should be considered when estimating CO emission from compost-amended soils. [ABSTRACT FROM AUTHOR]

Nitrogen isotope abundance ( δN) of paddy rice ( Oryza sativa L.) grown for 110 days after transplanting (DAT) under field conditions with ammonium sulfate (AS with −0.4‰ as a synthetic fertilizer), pig manure compost (PMC with 15.3‰ as a livestock manure compost), and hairy vetch (HV with −0.5‰ as a green manure) was investigated to test the possible use of δN technique in discriminating organically grown from conventionally grown rice. At 15 DAT, the δN of whole rice decreased ( P < 0.05) in the order of 10.5‰ for PMC > 5.5‰ for control (without N input) > 4.0‰ for HV > 1.8‰ for AS. This difference seemed to reflect primarily the δN signal of N sources. Although differences in δN of rice grown with isotopically distinct N inputs (i.e. PMC vs. AS and PMC vs. HV) became smaller over time, the difference (2.8 and 3.0‰ difference at harvest on 110 DAT, respectively) was still significant ( P < 0.05). However, there was no distinguishable difference between AS and HV treatment after 42 DAT. Such effect of N inputs on δN of whole rice was also observed for root, shoot, and grain at harvest. Therefore, our study suggests that it is possible to distinguish rice grown with manure composts from that grown with synthetic fertilizers. However, if green manure of preceding N-fixing plants is used as the N source, δN of rice may not be a good surrogate of N sources. [ABSTRACT FROM AUTHOR]

We examined the effect of soil salinity on the degradation of chlorpyrifos and the residual effect of chlorpyrifos and its metabolites on soil P fractionation during 60-day aerobic incubation. A sandy loam soil (Typic Psammaquents) was collected from the Daeho reclaimed tideland and two-thirds of the soil was applied with Na salt to get three different soil salinity levels: 4.6 (low, EL), 9.7 (medium, EM), and 14.4 (high, EH) dS m. Estimated half-lives for chlorpyrifos degradation were 7.1 in EL, 10.0 in EM and 16.9 days in EH soils. During the degradation of chlorpyrifos in soil, microbial activity decreased by increasing soil salinity and its inhibitory effect increased with time. In contrast, the addition of chlorpyrifos did not inhibit soil alkaline phosphatase (SAP) activity, which was higher in EH than in control soils. Chlorpyrifos added at a rate of 5.0 mg a.i. kg dry soil did not affect the distribution pattern of P fractions in control soils. Both an increase in soil salinity and soil sterilization increased the Ca-bound P fraction and decreased the occluded Fe + Al-bound P fraction with a significant interaction between soil salinity and sterilization. With time, the Ca-bound P fraction increased and organic- and occluded Fe + Al-bound P fractions decreased, while total-P, available-P, and non-occluded + adsorbed P fraction remained unchanged. Particularly, organic-P was mineralized more in EH than in control soils and the Ca-bound P fraction contained the highest inorganic P released. Mineralization of organic P and partitioning of released P in the recalcitrant Ca-bound P fraction increased by increasing soil salinity, while available P fraction remained unchanged, suggesting that the addition of chlorpyrifos at the currently recommended dosage level did not seem to considerably affect the available P fraction with low P leaching potential to waterways. [ABSTRACT FROM AUTHOR]

To test the possible use of tree ring chemical properties as proxies for precipitation acidity ([H+]), we investigated the relationships between tree ring chemistry (δ 13C, δ 15N, Ca-to-Al ratio, and N concentration) of Pinus densiflora and precipitation [H+] between 1992 and 2005 in an industrial area in the southwest region of South Korea. Statistical analyses showed that all tree ring chemistry parameters were significantly correlated with precipitation [H+]. Tree ring δ 13C was negatively correlated with precipitation acidity ( r = -0.67, P < 0.01), reflecting the photosynthetic fixation of 13C-depleted CO2 from fossil fuel combustion that would be the primary source of precipitation acidity. A positive correlation of N concentration ( r = 0.89, P < 0.001) and a negative correlation of δ 15N ( r = -0.63, P < 0.05) in tree rings with precipitation acidity most likely reflected the influence of 15N-depleted N compounds deposited via precipitation. The Ca-to-Al ratio was negatively ( r = -0.58, P < 0.05) correlated with precipitation acidity, indicating that soil acidification caused the loss of Ca from the soil and solubilization of Al resulting from acid precipitation. Such relationships suggest that δ 13C, δ 15N, N concentration, and Ca-to-Al ratio in tree rings can be reliably used to evaluate the impact of acid precipitation on the studied P. densiflora stands. [ABSTRACT FROM AUTHOR]

Electrical conductivity of saturated soil extracts (ECe) in three reclaimed tideland (RTL) soils on the west coast of Korea decreased with time since reclamation, indicating natural desalinization through leaching of salts by precipitation water. Soil N concentration increased with decreasing ECe. With the increase in soil N concentration, the δ15N decreased, likely caused by the input of 15N-depleted N sources. As N2-fixing plant species were found in the oldest RTL, atmospheric N2 fixation likely contributed to the increase in soil N concentration in the oldest RTL. Negative δ15N (−7.1 to −2.0‰) of total inorganic N (NH4 ++NO3 −) and published data on N deposition near the study area indicate that atmospheric N deposition might be another source of N in the RTLs. Meanwhile, the consistently negative δ15N of soil NO3 − excluded N input from chemical fertilizer through groundwater flow as a potential N source, since NO3 − in groundwater generally have a positive δ15N. The patterns of δ15N of NH4 + (+2.3 to +5.1‰) and NO3 − (−9.2 to −5.0‰) suggested that nitrification was an active process that caused 15N enrichment in NH4 + but denitrification was probably minimal which would otherwise have caused 15N enrichment in NO3 −. A quantitative approach on N budget would provide a better understanding of soil N dynamics in the studied RTLs. [ABSTRACT FROM AUTHOR]

To examine the effect of organic amendment application on the fate of inorganic-N accumulated in a vegetable field soil during conversion from inorganic to organic input, a pot experiment using 15N-labeled soil was conducted. The soil was labeled with 15N through addition of urea-15N (98 atom % 15N) and was then incubated for 1 year resulting in inorganic soil-N concentration and 15N abundance of 211 mg kg-1 soil and 4.950 atom %, respectively. Chinese cabbage [Brassica campestris (L.) Samjin] plants were grown in the labeled soil for 30 and 60 days after application of organic amendment at the rates of 0 (control), 200, 400, and 600 mg N kg-1 soil. Although organic amendment application did not show any significant effect on the uptake efficiency of inorganic-N by Chinese cabbage during the first 30 days, it significantly (P<0.05) increased inorganic-N uptake efficiency as well as total-N uptake and dry matter yield at the end of the 60-day growth period. Application of the organic amendment also increased microbial immobilization of inorganic-N in both growth periods. Between 30 and 60 days of growth, however, the amount of immobilized N from the inorganic-15N pool decreased, indicating re-mineralization of previously immobilized N. Although the amount of inorganic-15N lost was virtually the same among treatments at day 30, increased immobilization of inorganic-15N caused by organic amendment application led to the higher retention of inorganic-N in the soil and less loss of N at day 60 as compared to the control. These results indicate that increased immobilization by organic amendment application in the early growth season and the subsequent gradual re-mineralization may play an important role in increasing plant uptake of inorganic-15N, while minimizing N loss. [ABSTRACT FROM AUTHOR]

It has been accepted that variations in stable N isotope ratios (15N/14N) can potentially provide useful, sometimes unique, information on the sources of nitrate in groundwater, because N isotope compositions are generally different among various N pools such as atmospheric N2, soil, chemical fertilizer, and manure. However, this review strongly suggests that interpretation of the nitrate source based on a single measurement of δ15N may not be accurate because the isotopic composition of groundwater nitrate is a function of its source and any isotope fractionation that may occur during its generation or transport to groundwater. This review, therefore, shows that to evaluate the nitrate contamination source using δ15N technique, it is more reasonable to use correlation between the concentrations and δ15N of NO3 −. For example, a positive correlation indicates15N-enriched source such as manure, while15N-depleted source results in a negative correlation. The correlation analysis can also be used in evaluation of denitrification and nitrification. Denitrification is a key process affecting δ15N of NO3 −, i.e. if significant amount of nitrate is removed through denitrification, it is not easy to discriminate fertilizer-derived nitrate from manure-or compost-derived one because denitrification increase the δ15N of the remaining NO3 −. Therefore, it is important to assess whether denitrification may be occurring or not when evaluating isotope data on nitrate. By using dual (δ15N air and δ18O vsmow ) isotopic indicators, denitrification can be evaluated more accurately. [ABSTRACT FROM AUTHOR]

Investigates the effect of inorganic fertilizer and composted manure amendments on the nitrogen isotope composition of crop and soil, maize was cultivated under greenhouse conditions for 30, 40, 50, 60, and 70 days. Use of composted pig manure and urea were applied.

To evaluate the nitrate contamination sources of unconfined groundwater in the North Han River basin (127°45′E, 37°55′N), groundwater samples were collected monthly for three years (1997–1999) from 20 wells, and analyzed for the concentration (n=599) and δ15N (n=96) of NO3−N. Frequency distribution of NO3−N concentration showed that 43.9% of samples exceeded the national standard for drinking water (10 mg NO3−N L−1). During dry season between October and March, only 36.1% of a total of 296 samples had NO3−N concentration above 10 mg L−1. However, 51.5% of a total of 303 samples exceeded the standard level during wet season between April and September. Concentrations of nitrate increased with direction of groundwater flow. Wells located in vicinity of livestock feedlots showed consistently high nitrate concentration irrespective of precipitation pattern. The δ15N signatures of NO showed that in general, both15N-depleted source (e.g., chemical fertilizer) and15N-enriched source (e.g., compost and manure) impacted groundwater quality concurrently. The δ15N ranges of groundwater NO were +1.5–+12.9‰ in dry season and +3.2–+9.9‰ in wet season. These δ15N data suggested that the effects of compost and/or manure on nitrate concentration were apparent in dry season. A positive correlation (r2=0.32) between N concentration and δ15N of NO in dry season also suggested that nitrate concentration increased with increasing loading of nitrate from compost and/or manure wastewater. On the other hand, the relatively narrow range of δ15N and high nitrate concentration in wet season suggested that increased flush of nitrate derived from mixed sources such as fertilizer, compost, and manure during storm event resulted in high nitrate concentration. In this area, neither high δ15N values nor a negative correlation between δ15N and N concentration of NO, indicating denitrification was observed because of the coarse textured soil matrix. Therefore, reduction of nitrogen inputs through curtailment of fertilizer and compost application rates and appropriate treatment of livestock manure are the most effective and practical ways to prevent groundwater contamination. [ABSTRACT FROM AUTHOR]

The temperature sensitivity (Q10) of heterotrophic soil respiration (RH) of forests affects terrestrial carbon (C) dynamics under climate change. However, the effects of changed chemistry of tree leaf litter (referred to as litter hereafter) under elevated atmospheric CO2 concentrations ([CO2]) on the Q10 of RH has not been explored. To fill the knowledge gap, the Q10 of RH was investigated through incubation experiments at three temperature levels using litters of pine (Pinus densiflora Siebold & Zucc.) and oak (Quercus variabilis Blume) that were produced under ambient ([CO2]a) and elevated ([CO2]e) [CO2]. Regardless of [CO2] conditions, pine litter had higher lignin but lower nonstructural carbohydrate (NSC), calcium (Ca), and manganese (Mn) concentrations than oak, suggesting that pine litter has inherently poor chemistry. [CO2]e increased the ratios of lignin-to-nitrogen (lignin/N; by 58 and 122% for pine and oak, respectively) and C-to-N (C/N; by 47 and 125%, respectively) of litter through decreasing litter N concentration. For soils amended with [CO2]a-litter, Q10 was greater for pine (1.54) than oak (1.39) litters in agreement with the kinetic theory on the substrate quality-Q10 relationship. However, amending [CO2]e-litter decreased Q10 for pine (1.44) but marginally increased Q10 for oak (1.44). The decreased Q10 for pine by [CO2]e could be attributed to the inherently poor litter chemistry (e.g., high lignin, and low NSC, Ca, and Mn concentrations). Our study shows that the changed litter chemistry by [CO2]e modifies Q10 of RH of litter-amended soils. [ABSTRACT FROM AUTHOR]