Are there memory effects on greenhouse gas emissions (CO2_{2}, N2_{2}O and CH4_{4}) following grassland restoration?

A 5-year greenhouse gas (GHG) exchange study of the three major gas species (CO$_{2}$, CH$_{4}$ and N$_{2}$O) from an intensively managed permanent grassland in Switzerland is presented. Measurements comprise 2 years (2010 and 2011) of manual static chamber measurements of CH$_{4}$ and N$_{2}$O, 5 years of continuous eddy covariance (EC) measurements (CO$_{2}$–H$_{2}$O – 2010–2014), and 3 years (2012–2014) of EC measurement of CH$_{4}$ and N$_{2}$O. Intensive grassland management included both regular and sporadic management activities. Regular management practices encompassed mowing (three to five cuts per year) with subsequent organic fertilizer amendments and occasional grazing, whereas sporadic management activities comprised grazing or similar activities. The primary objective of our measurements was to compare pre-plowing to post-plowing GHG exchange and to identify potential memory effects of such a substantial disturbance on GHG exchange and carbon (C) and nitrogen (N) gains and losses. In order to include measurements carried out with different observation techniques, we tested two different measurement techniques jointly in 2013, namely the manual static chamber approach and the eddy covariance technique for N$_{2}$O, to quantify the GHG exchange from the observed grassland site. Our results showed that there were no memory effects on N$_{2}$O and CH$_{4}$ emissions after plowing, whereas the CO$_{2}$ uptake of the site considerably increased when compared to pre-restoration years. In detail, we observed large losses of CO$_{2}$ and N$_{2}$O during the year of restoration. In contrast, the grassland acted as a carbon sink under usual management, i.e., the time periods 2010–2011 and 2013–2014. Enhanced emissions and emission peaks of N$_{2}$O (defined as exceeding background emissions 0.21 ± 0.55 nmol m$^{-2}$ s$^{-1}$ (SE = 0.02) for at least 2 sequential days and the 7 d moving average exceeding background emissions) were observed for almost 7 continuous months after restoration as well as following organic fertilizer applications during all years. Net ecosystem exchange of CO$_{2}$ (NEECO$_{2}$) showed a common pattern of increased uptake of CO$_{2}$ in spring and reduced uptake in late fall. NEECO$_{2}$ dropped to zero and became positive after each harvest event. Methane (CH$_{4}$) exchange fluctuated around zero during all years. Overall, CH$_{4}$ exchange was of negligible importance for both the GHG budget and the carbon budget of the site. Our results stress the inclusion of grassland restoration events when providing cumulative sums of C sequestration potential and/or global warming potential (GWP). Consequently, this study further highlights the need for continuous long-term GHG exchange observations as well as for the implementation of our findings into biogeochemical process models to track potential GHG mitigation objectives as well as to predict future GHG emission scenarios reliably

N2O emissions from California farmlands: A review

Of the greenhouse gases emitted from cropland, nitrous oxide (N2O) has the highest global warming potential. The state of California acknowledges that agriculture both contributes to and is affected by climate change, and in 2016 it adopted legislation to help growers reduce emissions of greenhouse gases, explicitly including N2O. Nitrous oxide emissions can vary widely due to environmental and agronomic factors with most emission estimates coming from temperate grain systems. There is, however, a dearth of emission estimates from perennial and vegetable cropping systems commonly found in California\u27s Mediterranean climate. Therefore, emission factors (EFs) specific to California conditions are needed to accurately assess statewide N2O emissions and mitigation options. In this paper, we review 16 studies reporting annual and seasonal N2O emissions. This data set represents all available studies on measured emissions at the whole field scale and on an event basis. Through this series of studies, we discuss how such farm management and environmental factors influence N2O emissions from California agriculture and may serve as a basis for improved EF calculations

Early season N2O emissions under variable water management in rice systems: source-partitioning emissions using isotope ratios along a depth profile

Soil moisture strongly affects the balance between nitrification, denitrification and N2O reduction and therefore the nitrogen (N) efficiency and N losses in agricultural systems. In rice systems, there is a need to improve alternative water management practices, which are designed to save water and reduce methane emissions but may increase N2O and decrease nitrogen use efficiency. In a field experiment with three water management treatments, we measured N2O isotope ratios of emitted and pore air N2O (δ15N, δ18O and site preference, SP) over the course of 6 weeks in the early rice growing season. Isotope ratio measurements were coupled with simultaneous measurements of pore water NO−3, NH+4, dissolved organic carbon (DOC), water-filled pore space (WFPS) and soil redox potential (Eh) at three soil depths. We then used the relationship between SP × δ18O-N2O and SP × δ15N-N2O in simple two end-member mixing models to evaluate the contribution of nitrification, denitrification and fungal denitrification to total N2O emissions and to estimate N2O reduction rates. N2O emissions were higher in a dry-seeded + alternate wetting and drying (DS-AWD) treatment relative to water-seeded + alternate wetting and drying (WS-AWD) and water-seeded + conventional flooding (WS-FLD) treatments. In the DS-AWD treatment the highest emissions were associated with a high contribution from denitrification and a decrease in N2O reduction, while in the WS treatments, the highest emissions occurred when contributions from denitrification/nitrifier denitrification and nitrification/fungal denitrification were more equal. Modeled denitrification rates appeared to be tightly linked to nitrification and NO−3 availability in all treatments; thus, water management affected the rate of denitrification and N2O reduction by controlling the substrate availability for each process (NO−3 and N2O), likely through changes in mineralization and nitrification rates. Our model estimates of mean N2O reduction rates match well those observed in 15N fertilizer labeling studies in rice systems and show promise for the use of dual isotope ratio mixing models to estimate N2 losses.ISSN:1726-4170ISSN:1726-417

Early season N2O emissions under variable water management in rice systems: source-partitioning emissions using isotope ratios along a depth profile

Soil moisture strongly affects the balance between nitrification, denitrification and N2O reduction and therefore the nitrogen (N) efficiency and N losses in agricultural systems. In rice systems, there is a need to improve alternative water management practices, which are designed to save water and reduce methane emissions but may increase N2O and decrease nitrogen use efficiency. In a field experiment with three water management treatments, we measured N2O isotope ratios of emitted and pore air N2O (delta N-15, delta O-18 and site preference, SP) over the course of 6 weeks in the early rice growing season. Isotope ratio measurements were coupled with simultaneous measurements of pore water NO3-, NH4+, dissolved organic carbon (DOC), water-filled pore space (WFPS) and soil redox potential (Eh) at three soil depths. We then used the relationship between SP x delta O-18-N2O and SP x delta N-15-N2O in simple two end-member mixing models to evaluate the contribution of nitrification, denitrification and fungal denitrification to total N2O emissions and to estimate N2O reduction rates. N2O emissions were higher in a dry-seeded+alternate wetting and drying (DS-AWD) treatment relative to water-seeded+alternate wetting and drying (WS-AWD) and water-seeded+conventional flooding (WS-FLD) treatments. In the DS-AWD treatment the highest emissions were associated with a high contribution from denitrification and a decrease in N2O reduction, while in the WS treatments, the highest emissions occurred when contributions from denitrification/nitrifier denitrification and nitrification/fungal denitrification were more equal. Modeled denitrification rates appeared to be tightly linked to nitrification and NO3- availability in all treatments; thus, water management affected the rate of denitrification and N2O reduction by controlling the substrate availability for each process (NO3- and N2O), likely through changes in mineralization and nitrification rates. Our model estimates of mean N2O reduction rates match well those observed in N-15 fertilizer labeling studies in rice systems and show promise for the use of dual isotope ratio mixing models to estimate N-2 losses

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Mitigating Nitrous Oxide Emissions from Corn Cropping Systems in the Midwestern U.S.: Potential and Data Gaps

One of the unintended nitrogen (N)-loss pathways from cropland is the emission of nitrous oxide (N₂O), a potent greenhouse gas and ozone depleting substance. This study explores the potential of alternative agronomic management practices to mitigate N₂O emissions from corn cropping systems in major corn producing regions in the U.S. and Canada, using meta-analysis. The use of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) in combination with the nitrification inhibitor Dicyandiamide (DCD) was the only management strategy that consistently reduced N₂O emissions, but the number of observations underlying this effect was relatively low. Manure application caused higher N₂O emissions compared to the use of synthetic fertilizer N. This warrants further investigation in appropriate manure N-management, particularly in the Lake States where manure application is common. The N₂O response to increasing N-rate varied by region, indicating the importance of region-specific approaches for quantifying N₂O emissions and mitigation potential. In general, more data collection on side-by-side comparisons of common and alternative management practices, especially those pertaining to N-placement, N-timing, and N-source, in combination with biogeochemical model simulations, will be needed to further develop and improve N₂O mitigation strategies for corn cropping systems in the major corn producing regions in the U.S

Mitigating Nitrous Oxide Emissions from Corn Cropping Systems in the Midwestern U.S.: Potential and Data Gaps

One of the unintended nitrogen (N)-loss pathways from cropland is the emission of nitrous oxide (N₂O), a potent greenhouse gas and ozone depleting substance. This study explores the potential of alternative agronomic management practices to mitigate N₂O emissions from corn cropping systems in major corn producing regions in the U.S. and Canada, using meta-analysis. The use of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) in combination with the nitrification inhibitor Dicyandiamide (DCD) was the only management strategy that consistently reduced N₂O emissions, but the number of observations underlying this effect was relatively low. Manure application caused higher N₂O emissions compared to the use of synthetic fertilizer N. This warrants further investigation in appropriate manure N-management, particularly in the Lake States where manure application is common. The N₂O response to increasing N-rate varied by region, indicating the importance of region-specific approaches for quantifying N₂O emissions and mitigation potential. In general, more data collection on side-by-side comparisons of common and alternative management practices, especially those pertaining to N-placement, N-timing, and N-source, in combination with biogeochemical model simulations, will be needed to further develop and improve N₂O mitigation strategies for corn cropping systems in the major corn producing regions in the U.S

Season and location–specific nitrous oxide emissions in an almond orchard in California

ISSN:1385-1314ISSN:1573-086