Direct Canopy Uptake of Atmospheric Reactive Nitrogen: A Significant Pathway for Airborne Nitrogen Input into Rice Paddy Ecosystems

Direct canopy uptake of atmospheric reactive nitrogen (ARN) is an important process, but the magnitude of ARN assimilation in agricultural ecosystems is unclear. We used a combination of a water-culture rice-growing system with a 15N tracer to investigate canopy uptake of ARN under field conditions. Gross uptake was quantified using the plant N partitioning approach, and the net uptake of ARN was estimated based on the system N balance. Gross ARN uptakes were 23.1 and 38.2 kg N·ha–1 during vegetative and reproductive growth, respectively. Although a certain amount of N was lost mainly from the rice canopy during the reproductive phase, the net gain of ARN was 34.3 kg N·ha–1 over the entire growing season, much higher than the present estimates of dry N deposition using an indirect inferential approach. Our results highlight the magnitude of direct canopy uptake of ARN in rice paddy ecosystems, an important N process that is rarely considered in present N budgets

Data_Sheet_1_Methanotrophy Alleviates Nitrogen Constraint of Carbon Turnover by Rice Root-Associated Microbiomes.docx

The bioavailability of nitrogen constrains primary productivity, and ecosystem stoichiometry implies stimulation of N2 fixation in association with carbon sequestration in hotspots such as paddy soils. In this study, we show that N2 fixation was triggered by methane oxidation and the methanotrophs serve as microbial engines driving the turnover of carbon and nitrogen in rice roots. 15N2-stable isotope probing showed that N2-fixing activity was stimulated 160-fold by CH4 oxidation from 0.27 to 43.3 μmol N g–1 dry weight root biomass, and approximately 42.5% of the fixed N existed in the form of 15N-NH4+ through microbial mineralization. Nitrate amendment almost completely abolished N2 fixation. Ecophysiology flux measurement indicated that methane oxidation-induced N2 fixation contributed only 1.9% of total nitrogen, whereas methanotrophy-primed mineralization accounted for 21.7% of total nitrogen to facilitate root carbon turnover. DNA-based stable isotope probing further indicated that gammaproteobacterial Methylomonas-like methanotrophs dominated N2 fixation in CH4-consuming roots, whereas nitrate addition resulted in the shift of the active population to alphaproteobacterial Methylocystis-like methanotrophs. Co-occurring pattern analysis of active microbial community further suggested that a number of keystone taxa could have played a major role in nitrogen acquisition through root decomposition and N2 fixation to facilitate nutrient cycling while maintaining soil productivity. This study thus highlights the importance of root-associated methanotrophs as both biofilters of greenhouse gas methane and microbial engines of bioavailable nitrogen for rice growth.</p

Nitrogen Removal Capacity of the River Network in a High Nitrogen Loading Region

Denitrification is the primary process that regulates the removal of bioavailable nitrogen (N) from aquatic ecosystems. Quantifying the capacity of N removal from aquatic systems can provide a scientific basis for establishing the relationship between N reduction and water quality objectives, quantifying pollution contributions from different sources, as well as recommending control measures. The Lake Taihu region in China has a dense river network and heavy N pollution; however, the capacity for permanent N removal by the river network is unknown. Here, we concurrently examined environmental factors and net N₂ flux from sediments of two rivers in the Lake Taihu region between July 2012 and May 2013, using membrane inlet mass spectrometry, and then established a regression model incorporating the highly correlated factors to predict the N removal capacity of the river network in the region. To test the applicability of the regression model, 21 additional rivers surrounding Lake Taihu were sampled between July and December 2013. The results suggested that water nitrate concentrations are still the primary controlling factor for net denitrification even in this high N loading river network, probably due to multicollinearity of other relevant factors, and thus can be used to predict N removal from aquatic systems. Our established model accounted for 78% of the variability in the measured net N₂ flux in these 21 rivers, and the total N removed through N₂ production by the river network was estimated at 4 × 10⁴ t yr^–1, accounting for about 43% of the total aquatic N load to the river system. Our results indicate that the average total N content in the river water discharged into Lake Taihu would be around 5.9 mg of N L^–1 in the current situation, far higher than the target concentration of 2 mg of N L^–1, given the total N load and the N removal capacity. Therefore, a much stronger effort is required to control the N pollution of the surface water in the region

Cooling colors below the ambient temperature

The colors of objects are generally originated from reflecting desired light in the desired direction and absorbing the undesired light, which will substantially produce heating. Many efforts have been made to focus on cooling the colorful objects. However, a cooling strategy to cool colorful objects beyond a limit of temperature below the ambient temperature while fully preserving the excellent color properties of high saturation and large viewing field is still a great challenge, as it is rather difficult to independently control the four light bands simultaneously: high diffusion of desired light, low absorption of undesired complementary visible light, low absorption of near-IR light, and high emission of mid-IR light. Inspired by Morpho butterflies, we reported here a robust configure consisting of a multilayer, a disorder structure, and a total reflection layer to cool colorful objects to overcome the challenge. Numerical simulations and experimental measurements demonstrated that our configure can cool a class of colorful objects to not only a temperature of around 2 °C below the ambient temperature, but also with ultra-high saturations (100%) and a wide range of viewing angles (±60°), indicating a great potential for energy sustainability of colorful objects such as buildings, vehicles, facilities, and equipment

P‑type Doping in Large-Area Monolayer MoS₂ by Chemical Vapor Deposition

Molybdenum disulfide (MoS2) with excellent properties has been widely reported in recent years. However, it is a great challenge to achieve p-type conductivity in MoS2 because of its native stubborn n-type conductivity. Substitutional transition metal doping has been proved to be an effective approach to tune their intrinsic properties and enhance device performance. Herein, we report the growth of Nb-doping large-area monolayer MoS2 by a one-step salt-assisted chemical vapor deposition method. Electrical measurements indicate that Nb doping suppresses n-type conductivity in MoS2 and shows an ambipolar transport behavior after annealing under the sulfur atmosphere, which highlights the p-type doping effect via Nb, corresponding to the density functional theory calculations with Fermi-level shifting to valence band maximum. This work provides a promising approach of two-dimensional materials in electronic and optoelectronic applications

Greenhouse gas emission intensity (GHGI) under different fertilization treatments in the rice-wheat cropping system.

Greenhouse gas emission intensity (GHGI) under different fertilization treatments in the rice-wheat cropping system.</p

Dissimilatory Nitrate Reduction Processes in Typical Chinese Paddy Soils: Rates, Relative Contributions, and Influencing Factors

Using soil slurry-based ¹⁵N tracer combined with N₂/Ar technique, the potential rates of denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA), and their respective contributions to total nitrate reduction were investigated in 11 typical paddy soils across China. The measured rates of denitrification, anammox, and DNRA varied from 2.37 to 8.31 nmol N g^–1 h^–1, 0.15 to 0.77 nmol N g^–1 h^–1 and 0.03 to 0.54 nmol N g^–1 h^–1, respectively. The denitrification and anammox rates were significantly correlated with the soil organic carbon content, nitrate concentration, and the abundance of <i>nosZ</i> genes. The DNRA rates were significantly correlated with the soil C/N, extractable organic carbon (EOC)/NO₃^– ratio, and sulfate concentration. Denitrification was the dominant pathway (76.75–92.47%), and anammox (4.48–9.23%) and DNRA (0.54–17.63%) also contributed substantially to total nitrate reduction. The N loss or N conservation attributed to anammox and DNRA was 4.06–21.24 and 0.89–15.01 g N m^–2 y^–1, respectively. This study reports the first simultaneous investigation of the dissimilatory nitrate reduction processes in paddy soils, highlighting that anammox and DNRA play important roles in removing nitrate and should be considered when evaluating N transformation processes in paddy fields

Total crop yield kg ha^-1 for the rice-wheat cropping system.

Total crop yield kg ha-1 for the rice-wheat cropping system.</p

MIWI RK mutation does not affect the expression and localization of MILI and TDRKH.

(A) Expressions of MIWI, MILI, and TDRKH in adult testes are revealed by Western blotting. β-actin is a loading control. Quantification of intensity of MIWI is shown under the blot (the one in wildtype testis is set as 1.000 after normalization with β-actin). (B) Testes from indicated mice were immunostained using MILI or TDRKH antibodies. DNA was stained by DAPI. Scale bar, 20 μm. Results shown in (A) and (B) are representative of 3 biological replicates. (TIF)</p

Effects of fertilizer application schemes and soil environmental factors on nitrous oxide emission fluxes in a rice-wheat cropping system, east China - Fig 2

Seasonal variation in (a) daily soil temperature°C (0–10 cm), and water-filled pore space (WFPS %), and (b) daily changes in soil electrical conductivity (EC, dS/m) in the rice-wheat cropping system from 2012–2015.</p