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Highlights: [•] Comparison of carbon exchange process and carbon budget between two semiarid ecosystems. [•] PPFD was the major driver for diurnal variation of NEE while NDVI was mainly responsible for seasonal variation of NEE. [•] Number of precipitation event was correlated well with annual carbon uptake. [•] Drought in most active growth period was more crucial for carbon exchange. [Copyright &y& Elsevier]

Seasonal and interannual variations of evapotranspiration (ET) and energy exchange were estimated over degraded grassland and cropland land surfaces in a semiarid region of northeastern China using the eddy covariance technique from 2003 to 2008. The peak daily ET, which occurred in August, was 1.5-4.5 mm day−1 for the degraded grassland and 1.5-5.5 mm day−1 for the cropland land surface. Annual cumulative ET was roughly equal to annual precipitation at both sites. However, the annual cumulative ET at the cropland site was slightly larger (about 10-30 mm) than it was at the grassland at the end of each year. More water might come from irrigation at seedtime and from the soil. With the factor analysis technique, the results revealed that the atmospheric water demand was the most important factor in the ET process on a half-hour time scale in this semiarid area. On a seasonal time scale, ET was greatly constrained by surface conductance and precipitation; on an annual time scale, ET was greatly constrained by the total amount of precipitation at both sites. The accuracy of ET estimation using the Penman-Monteith formula in this semiarid area was also discussed. [ABSTRACT FROM AUTHOR]

P-Arylation in water has been developed via cross-coupling of aryl halides with diphenylphosphine oxide (Ph2P(O)H) and (RP)-(−)-menthyl benzylphosphinate catalyzed by NiCl2·6H2O/Zn under relatively mild conditions. [ABSTRACT FROM AUTHOR]

Analytical solutions of convective waves in the convective boundary layer (CBL) were obtained with two-layer linearized atmospheric equations including Rayleigh friction, which represents the turbulent viscosity in the lower CBL. The analytical model shows that the interaction between the convection in the lower layer and gravity waves in the upper layer is one of the causes for the formation of convective bands. The flow and temperature fields obtained by the analytical model present the main characteristics of convective bands found in field observations. We have also investigated the influences of atmospheric conditions on the characteristics of the bands. Results accord with previous knowledge about these phenomena. [ABSTRACT FROM AUTHOR]

Abstract  A roving tower concept was used to compare a semi-arid grassland site in Inner Mongolia (China), which was fenced in 1979 and ungrazed thereafter (UG79) with differently grazed semi-arid steppe ecosystems. The study was conducted during three consecutive years characterised by contrasting precipitation. The different grazing intensities included continuously and moderately grazed (CG), winter grazed (WG), and heavily grazed (HG). Here, we compare the energy fluxes and surface parameters that characterise the differently managed plots. The main focus is on sensible heat flux (H), available energy (AE), surface temperature (T s ), and surface albedo (α). Systematic errors were excluded by a side-to-side intercomparison of the instruments, and systematic climatic differences were minimised by the close distance between the fixed and the roving eddy covariance tower. Statistically, AE and T s were always significantly different between two simultaneously measured grazing intensities. Whereas AE was higher at UG79 in all years (mean difference of about 19Wm−2), T s was typically lower at UG79 (mean differences of 0.4°C to about 2°C). The exception was the end of the vegetation period in 2004 when T s was 0.6°C higher at UG79 compared to CG. At UG79 α was typically significantly lower, and H was typically significantly higher. Consequently, latent heat fluxes (both as energy balance residual and directly measured) do not differ much between the different grazing intensities. It is concluded, that (1) the roving tower concept is able to detect differences due to grazing, (2) differences between the sites can be attributed to real surface differences, and (3) differences due to grazing intensities are small compared to interannual differences in surface fluxes. [ABSTRACT FROM AUTHOR]

DEAD-box proteins comprise a large protein family with members from all kingdoms and play important roles in all types of processes in RNA metabolism. In this study, a rice gene OsBIRH1, which encodes a DEAD-box RNA helicase protein, was cloned and characterized. The predicted OsBIRH1 protein contains a DEAD domain and all conserved motifs that are common characteristics of DEAD-box RNA helicases. Recombinant OsBIRH1 protein purified from Escherichia coli was shown to have both RNA-dependent ATPase and ATP-dependent RNA helicase activities in vitro. Expression of OsBIRH1 was activated in rice seedling leaves after treatment with defence-related signal chemicals, for example benzothiadiazole, salicylic acid, l-aminocyclopropane-1-carboxylic acid, and jasmonic acid, and was also up-regulated in an incompatible interaction between a resistant rice genotype and the blast fungus, Magnaporthe grisea. Transgenic Arabidopsis plants that overexpress the OsBIRH1 gene were generated. Disease resistance phenotype assays revealed that the OsBIRH1-overexpressing transgenic plants showed an enhanced disease resistance against Alternaria brassicicola and Pseudomonas syringae pv. tomato DC3000. Meanwhile, defence-related genes, for example PR-1, PR-2, PR-5, and PDF1.2, showed an up-regulated expression in the transgenic plants. Moreover, the OsBIRH1 transgenic Arabidopsis plants also showed increased tolerance to oxidative stress and elevated expression levels of oxidative defence genes, AtApx1, AtApx2, and AtFSD1. The results suggest that OsBIRH1 encodes a functional DEAD-box RNA helicase and plays important roles in defence responses against biotic and abiotic stresses. [ABSTRACT FROM PUBLISHER]

The Surface Urban Energy and Water Balance Scheme (SUEWS) has recently been introduced to include a bottomup approach to modelling carbon dioxide (CO2) emissions and sink in urban areas. In this study, SUEWS is evaluated against radiation flux observations and eddy covariance (EC) measured turbulent fluxes of sensible heat (QH), latent heat (QE), and CO2 (FC) at a densely built neighborhood in Beijing. The model sensitivity to maximum conductance (gmax) and leaf area index (LAI) is examined. Site-specific gmax is obtained from observations over local vegetation species, and LAI parameters by optimization with remotely sensed LAI obtained from a MODIS/Terra data product. For simulation of anthropogenic CO2 components, local traffic and population data are collected. In model evaluation, the mismatch between the measurement source area and simulation domain is also considered. Using the optimized gmax and LAI, the modelling of heat fluxes is noticeably improved, showing higher correlation with observations, lower bias, and more realistic seasonal dynamics of QE and QH. In comparison to heat fluxes, the FC module shows lower sensitivity to the choice of gmax and LAI. This can be explained by the low relative contribution of vegetation to net FC in the modelled area. SUEWS successfully reproduces the average diurnal cycle of FC and annual cumulative sums. Depending on the size of the simulation domain, the modelled annual accumulated FC ranges from 7.2 to 8.5 kg C m-2 yr-1, when compared to 7.5 kg C m-2 yr-1 observed by EC. Traffic is the dominant CO2 source, contributing 63-73% to the annual total CO2 emissions, followed by human metabolism (14-18%), respiration released by vegetation and soil (6-11%) and building heating (6-9%). Vegetation photosynthesis offsets only 4-8% of the total CO2 emissions. We highlight the importance of choosing optimal LAI parameters and gmax when SUEWS is used to model surface fluxes. The FC module of SUEWS is a promising tool in quantifying urban CO2 emissions at the local scale, and therefore assisting to mitigate urban CO2 emissions. [ABSTRACT FROM AUTHOR]

Detecting the influences of land management on seasonal dynamics and interannual variabilities of grassland surface reflectance is of scientific and practical importance as it can help to monitor grazing effects on the grassland ecosystem. We conducted spectral reflectance measurements at five differently grazed sites in Inner Mongolia, China, during the growing seasons of 2005 and 2006 using a portable, highly resolving spectrometer. Through analyses of the measured surface reflectance spectra and the derived visible albedo and NDVI, we found that grazing influences the reflectance spectrum shape and affects the visible albedo and NDVI seasonal pattern; visible albedo and NDVI of grazed sites are more sensitive to precipitation than that of ungrazed sites. In addition, we observed a well-defined linear relationship between total shortwave and visible (PAR) albedo, with R = 0.83 and R = 0.94 for 2005 and 2006, respectively, and between NDVI and total shortwave albedo with R = −0.92. Thus, NDVI spectrometer measurements and total shortwave albedo pyranometer measurements are interchangeable when addressing different grazing intensities. [ABSTRACT FROM AUTHOR]

Parameterization of turbulent flux from bare-soil and undercanopy surfaces is imperative for modeling land–atmosphere interactions in arid and semiarid regions, where flux from the ground is dominant or comparable to canopy-sourced flux. This paper presents the major characteristics of turbulent flux transfers over seven bare-soil surfaces. These sites are located in arid, semiarid, and semihumid regions in Asia and represent a variety of conditions for aerodynamic roughness length (z0m; from <1 to 10 mm) and sensible heat flux (from -50 to 400 W m-2). For each site, parameter kB-1 [=ln(z0m/z0h), where z0h is the thermal roughness length] exhibits clear diurnal variations with higher values during the day and lower values at night. Mean values of z0h for the individual sites do not change significantly with z0m, resulting in kB-1 increasing with z0m, and thus the momentum transfer coefficient increases faster than the heat transfer coefficient with z0m. The term kB-1 often becomes negative at night for relatively smooth surfaces (z0m ∼ 1 mm), indicating that the widely accepted excess resistance for heat transfer can be negative, which cannot be explained by current theories for aerodynamically rough surfaces. Last, several kB-1 schemes are evaluated using the same datasets. The results indicate that a scheme that can reproduce the diurnal variation of kB-1 generally performs better than schemes that cannot. [ABSTRACT FROM AUTHOR]

Three velocity components and temperature were measured using three-dimensional sonic anemometers/thermometers at two levels, above and within a forest canopy, in the Changbai Mountains of northeast China. Turbulence spectral structure, local isotropy and dissipation rates above and within the forest canopy were calculated using the eddy correlation method. Results show that the normalized turbulent spectral curves have 2/3 slopes in the inertial subrange. While the shapes of the spectra are in good agreement with the Kansas flat terrain results, the atmospheric turbulence is anisotropic above the forest canopy. Due to breaking down of large eddies by the foliage, branches and trunks, the spectral peak frequencies for velocity and temperature are higher within than above the forest canopy. Compared with measurements from previous studies over flat terrain, the velocity and temperature spectra above and inside the forest canopy appear to shift toward higher frequencies. The turbulence is approximately isotropic in the inertial subrange within the forest canopy, and is anisotropic above the forest canopy. The turbulent kinetic energy and heat energy dissipation rates above and inside the forest canopy are much larger than those obtained by Kaimal and Hogstrom over grassland and grazing land. The distinct features in the results of the present experiment may be attributed to the dynamic forcing caused by the rough surface of the forest canopy. [ABSTRACT FROM AUTHOR]