Interactions of water and nitrogen addition on soil microbial community composition and functional diversity depending on the inter-annual precipitation in a Chinese steppe

Water and nitrogen are primary limiting factors in semiarid grassland ecosystems. Our knowledge is still poor regarding the interactive effects of water and N addition on soil microbial communities, although this information is crucial to reveal the mechanisms of the terrestrial ecosystem response to global changes. We addressed this problem by conducting a field experiment with a 15% surplus of the average rainfall under three levels of N addition（50, 100, and 200 kg N ha–1 yr–1） in two consecutive years in Inner Mongolia, China. Microbial community composition and functional diversity were analyzed based on phospholipid fatty acids（PLFA） and BIOLOG techniques, respectively. The results showed that water addition did not affect the soil microbial community composition, but much more yearly precipitation generally decreased the PLFA concentration, which implied a fast response of soil microbes to changes of water condition. Soil fungi was depressed only by N addition at the high level（200 kg N ha–1 yr–1） and without hydrologic leaching, while Gram-negative bacteria was suppressed probably by plant competition at high level N addition but with hydrologic leaching. The study found unilateral positive/negative interactions between water and N addition in affecting soil microbial community, however, climate condition（precipitation） could be a significant factor in disturbing the interactions. This study highlighted that：（1） The sustained effect of pulsed water addition was minimal on the soil microbial community composition but significant on the microbial community functional diversity and（2） the complex interaction between water and N addition on soil microbial community related to the inter-annual variation of the climate and plant response.

Improvement on Mixograph test through water addition and parameter conversions

To improve Mixograph testing effect, Farinograph measurements were adopted as a quality standard and changes in water absorption and parameter conversion in Mixograph test were explored. Comparative study showed that increasing water absorption to about 73% and converting original parameters to compound parameters in Mixograph tests signiifcantly increased their predictive power for lfour quality. These efforts also enabled the adoption of ifxed water addition level in Mixograph test and simpliifed the test procedure signiifcantly. With the success in parameter conversions, Mixograph test results were successful y described by Farinograph parameters, which al ow breeders to compare and exchange test results easily. Al these changes optimized the ofifcial method of Mixograph test with simpliifed procedure and enhanced reliability and made the Mixograph being the superior tool for quality assessment in wheat-breeding programs.

Research on the effect of the component proportion in the new water mist additive on firefighting performance

Water mist technology provides efficient firefighting performance while there is still room for improvement. So varieties of additives have been studied in recent years both at home and abroad. The self-made additives are used to compare the firefighting performance of diesel and heptane fire in open space. By adjusting the concentration of substance in the additives and conducting the experiment under the pressure of 0.3 MPa,0.5 MPa and 0.7 MPa,extinguish time and temperature are measured in the experiment. Through the experiments using different fuels,it can be found when the fuel is heptane that has a lower ignition point and a higher evaporation rate, the water mist additive can still significantly improve the firefighting performance. According to the data based on different concentrations of fluorinated surfactants,we find that fluorinated surfactants are the main substance to improve the performances by changing physical property of water mist. Optimal proportion of the additives for firefighting performance is found by experiment results.

Effect of Water Addition on Rheological Behaviour of BauxiteBased Low-cement Castables

Water addition has direct impact on castables and needs to be under control placement and properties, In this work, two rheological properties, flow resistance and torque viscosity, have been measured against time, with different water addition in the same bauxile-based LC Castable mix. The flow resistance indicates the mobility, whereas the torque viscosity dictates the stability of a castable during installation. It has been observed that with 6.0wt% water addition, such a mix possesses good vibration castable characteristics; with 6.5 wt%, it shows good self-flow castable characteristics; and with 7.0 wt%, it can be a good pumpable castable, in every case with comparable mechanical properties. While with 7.5 wt% water addition, the properties of such castable are definitively impaired.

Improvement of Emissions and Burning Limits in Burner Combustion using an Injector on the Concept of Fuel-Water Internally Rapid Mixing

This study tried to apply biomass fuel to clean burner combustion under high load conditions by water addition. A newly developed injector mixes fuel rapidly with water inside of the injector with support of atomizing air. The mixture composed of three-fluid is injected as spray into a flame stabilizer of burner. Investigation of emission performance of this injector shows that the internally rapid mixing type of injector is hopeful technique to introduce water into burner combustion. Combustion by this injector emits exceedingly less particulate matters at high load. NOx emission is strongly dependent on water flow rate.

Precipitation Pulses and Soil CO_2 Emission in Desert Shrubland of Artemisia ordosica on the Ordos Plateau of Inner Mongolia,China

Precipitation is the major driver of ecosystem functions and processes in semiarid and arid regions. In such waterlimited ecosystems, pulsed water inputs directly control the belowground processes through a series of soil drying and rewetting cycles. To investigate the effects of sporadic addition of water on soil CO2 effux, an artificial precipitation event （3 mm） was applied to a desert shrub ecosystem in the Mu Us Sand Land of the Ordos Plateau in China. Soil respiration rate increased 2.8 4.1 times immediately after adding water in the field, and then it returned to background level within 48 h. During the experiment, soil CO2 production was between 2 047.0 and 7 383.0 mg m^-2. In the shrubland, soil respiration responses showed spatial variations, having stronger pulse effects beneath the shrubs than in the interplant spaces. The spatial variation of the soil respiration responses was closely related with the heterogeneity of soil substrate availability. Apart from precipitation, soil organic carbon and total nitrogen pool were also identified as determinants of soil CO2 loss in desert ecosystems.

Differential Responses of Ammonia-oxidizers Communities to Nitrogen and Water Addition in Stipa baicalensis Steppe,Inner Mongolia,Northern China

Atmospheric nitrogen deposition and precipitation as an important phenomenon of global climate change have a great impact on grassland ecosystems. However, little is known about how the soil ammonia-oxidizing microorganisms respond to the both changes. Ammonia oxidization is a crucial step in the soil nitrification and greatly inlfuenced by soil nitrogen availability. We used PCR and DGGE （denaturing gradient gel electrophoresis） approaches to investigate the responses of AOB （ammonia-oxidizing bacteria） 16S rRNA and AOA （ammonia-oxidizing archaea）amoA genes to nitrogen and water input inStipa baicalensis steppe, Inner Mongolia, northern China. After two years of nitrogen and water addition treatment, it was found that PNA （potential nitriifcation activity） was greatly enhanced by lower N fertilization treatment under water addition and higher N fertilization under no-water addition, while it decreased markedly in higher N fertilization under water addition. The community structure of AOB responded more sensitively to N fertilization and water input than AOA, resulting in the significantly decreased diversity in the AOB community along with a higher N fertilizer rate, but an obvious increase in the AOA community, demonstrating the active growth of AOA in higher N fertilization soils. Phylogenetic analysis showed that AOB communities were dominated byNitrosospira clusters3, 4 andNitrososmonas clusters 6 under water addition andNitrosospira culsters 1, 3 and 4 and under no-water addition, while AOA communities were grouped intoCrenarchaeote clusters 1, 2 and 5 under no-water addition and Crenarchaeote clusters 1, 2 and water lineage under water addition. The differences between the two water addition regimes strongly suggest that water input acts as an important role in shifting AOA and AOB communities. Moreover, in contrast to the AOA, the diversity of AOB was negatively correlated with total N, NH4^＋, NO3^- and pH under water addition, implying a signiifcant N fertilization and water effect on shaping AOA and AOB communities. In conclusion, our studies suggested that N fertilization and water addition and their composite effects had signiifcantly changed AOB and AOA communities, meanwhile, AOB and AOA communities could develop a desirable complementary mechanism in response to external changes.

Interactive effects of water and nitrogen addition on soil microbial communities in a semiarid steppe

Aims Better understanding of microbial compositional and physiological acclimation mechanisms is critical for predicting terrestrial ecosystem responses to global change.The aim is to assess variations in soil microbial communities under future scenarios of changing precipitation and N deposition in a semiarid grassland of northern China.Methods In order to explicitly estimate microbial responses,a field experiment with water and N addition was established in April 2005 and continuously conducted for 4 years.Specifically,soil microbial community composition and microbial C utilization potential were determined by phospholipid fatty acid(PLFA)and community-level physiological profiles,respectively.Important Findings Water addition had no effects on the PLFA concentrations of grampositive(GP)and negative bacteria(GN),total bacteria and fungi.However,N addition caused significant reductions in the PLFA concentrations of GP,GN,total bacteria and fungi and thus decreased total PLFA of microbial communities.Moreover,there were interactive effects of water and N addition on GN/GPand the ratio of fungal to bacterial PLFA(F/B).In addition,synergistic effects were found between water and nitrogen in affecting microbial C utilization potentials,which implies that microbial C utilization potentials tend to be enhanced when both N and water availability are sufficient.Overall,the microbial responses to water and N addition support our hypothesis that water and N addition may be combined together to affect microbial communities in the semiarid grassland.

Controllable synthesis of different morphologies of CuO nanostructures for tribological evaluation as water-based lubricant additives

In this study,water soluble CuO nanostructures having nanobelt,nanorod,or spindle morphologies were synthesized using aqueous solutions of Cu(NO_(3))_(2)·3H_(2)O and NaOH by adjusting the type of surface modifier and reaction temperature.The effect of morphologies of these various CuO nanostructures as water‐based lubricant additives on tribological properties was evaluated on a UMT‐2 micro‐friction tester,and the mechanisms underlying these properties are discussed.The three different morphologies of CuO nanostructures exhibited excellent friction‐reducing and anti‐wear properties.Tribological mechanisms differed in the initial stage of frictional interactions,but in the stable stage,a tribochemical reaction film and adsorbed lubricious film on the rubbing surfaces played important roles in hindering direct contact between friction pairs,leading to improved tribological properties.

Nitrogen addition amplified water effects on species composition shift and productivity increase

Aims Water and nitrogen(N)are two key resources in dryland ecosystems,but they may have complex interactive effects on the community structure and ecosystem functions.How future precipitation(rainfall vs snowfall)change will impact aboveground net primary production(ANPP)is far from clear,especially when combined with increasing N availability.Methods In this study,we investigated changes in community productivity,abundance and aboveground biomass of two dominant plant functional groups(PFGs),i.e.perennial rhizome grasses(PR)and perennial bunchgrasses(PB)under the impacts of increased precipitation(rainfall vs snowfall)combined with N addition in a semiarid temperate steppe.Important Findings Summer rainfall augmentation marginally increased community ANPP,whereas it significantly increased the abundance and aboveground biomass of PR,but not those of PB.Summer rainfall addition increased the fraction of PR biomass(fPR)while decreased that of PB(fPB).Spring snow addition had no effect on aboveground biomass of either compositional PFG although it marginally increased community ANPP.Nitrogen addition significantly increased community ANPP with greater increase in PR under summer rainfall addition,indicating strong interactive effects on community ANPP largely by enhancing PR biomass.We also found a nonlinear increase in the positive effect of nitrogen addition on productivity with the increased precipitation amount.These findings indicate an amplified impact of precipitation increase on grassland productivity under the accelerated atmospheric N deposition in the future.

A green and convenient approach toward benzimidazole derivatives and their antimicrobial activity

N-Alkylated benzimidazole derivatives have been synthesized via the aza-Michael addition reactions of1H-benzimidazoles to a,b-unsaturated compounds in water and palladium acetate obviously promoted these transformations. The reported method, overcoming the inactivation of palladium under the equivalent nitrogenous conditions, has the advantages of convenient manipulation, atom-economy, as well as environmental friendliness. The bioactive results showed that butyl 3-（5,6-dimethyl-1Hbenzo[d]imidazol-1-yl）propanoate（3c） exhibited excellent inhibitory activity against Bacillus subtilis（MIC = 16 mg/m L） and Bacillus proteus（MIC = 8 mg/m L）. Therefore, this process would facilitate the construction of various potential bioactive compounds based on the benzimidazole scaffold under mild conditions.

The interactive effects of nitrogen addition and increased precipitation on gross ecosystem productivity in an alpine meadow

The ecological consequences of precipitation change and increased atmospheric nitrogen(N)deposition have profound impacts on ecosystem CO2 exchange in grassland ecosystems.Water and N can largely influence grassland productivity,community composition and ecosystem functions.However,the influences of water and N addition on the ecosystem CO2 exchange of alpine grassland ecosystems remain unclear.A field manipulative experiment with water and N additions was conducted in an alpine meadow on the Tibetan Plateau over 4 years with contrasting precipitation patterns.There were four treatments:control(Ctrl),N addition(N),water addition(W)and N and water addition(NW),each replicated three times.N addition,but not water addition,increased gross ecosystem productivity(GEP),plant biomass,community cover and community-weighted mean height.The responses of ecosystem CO2 exchange to water and N addition varied between the wet and dry years.Water addition had a positive effect on net ecosystem carbon exchange(NEE)due to a larger increase in GEP than in ecosystem respiration(ER)only in the dry year.On the contrary,N addition significantly enhanced ecosystem CO2 exchange only in the wet year.The increased GEP in N addition was attributed to the larger increase in NEE than ER.Moreover,N addition stimulated NEE mainly through increasing the cover of dominant species.Our observations highlight the important roles of precipitation and dominant species in regulating ecosystem CO2 exchange response to global environmental change in alpine grasslands.