Grazing during the grassland greenup period promotes plant species richness in alpine grassland in winter pastures

Although grazing is the most common use of grassland, the ecological function of grassland far exceeds its productivity. Therefore, the protection of plant diversity is of the utmost importance and cannot be ignored. Existing research on the effect of grazing on grassland mainly focuses on grazing intensity and the type of livestock, but the consequences of the timing of the grazing on the vegetation community remains unclear. We investigated plant community characteristics of winter pastures in alpine meadow with different grazing termination times (grazing before and during the grassland greenup periods) in Maqu County, eastern QTP. The results showed that vegetation height, coverage, aboveground biomass and Graminoid biomass were lower in grassland when grazing happened during the greenup period compared to grassland where grazing was terminated before the greenup period. However, the total plant species richness and forbs richness were higher in grassland with grazing during the greenup period compared to grassland without grazing during the greenup period. Our structural equation modeling reveals a potential indirect implication for the total plant species richness and forbs richness of winter pastures mainly through a decrease in the vegetation coverage and grass biomass abundance. Our findings imply that grazing during the grassland greenup period may facilitate the maintenance of plant diversity in winter pastures. These findings have important implications for grassland ecosystem functioning and for the conservation of plant diversity.https://www.frontiersin.org/journals/plant-sciencedm2022Mammal Research InstituteZoology and Entomolog

Coarse-Grained Model for Water Involving a Virtual Site

In this work, we propose a new coarse-grained (CG) model for water by combining the features of two popular CG water models (BMW and MARTINI models) as well as by adopting a topology similar to that of the TIP4P water model. In this CG model, a CG unit, representing four real water molecules, consists of a virtual site, two positively charged particles, and a van der Waals (vdW) interaction center. Distance constraint is applied to the bonds formed between the vdW interaction center and the positively charged particles. The virtual site, which carries a negative charge, is determined by the locations of the two positively charged particles and the vdW interaction center. For the new CG model of water, we coined the name “CAVS” (charge is attached to a virtual site) due to the involvment of the virtual site. After being tested in molecular dynamic (MD) simulations of bulk water at various time steps, under different temperatures and in different salt (NaCl) concentrations, the CAVS model offers encouraging predictions for some bulk properties of water (such as density, dielectric constant, etc.) when compared to experimental ones

Probing flexible conformations in molecular junctions by inelastic electron tunneling spectroscopy

The probe of flexible molecular conformation is crucial for the electric application of molecular systems. We have developed a theoretical procedure to analyze the couplings of molecular local vibrations with the electron transportation process, which enables us to evaluate the structural fingerprints of some vibrational modes in the inelastic electron tunneling spectroscopy (IETS). Based on a model molecule of Bis-(4-mercaptophenyl)-ether with a flexible center angle, we have revealed and validated a simple mathematical relationship between IETS signals and molecular angles. Our results might open a route to quantitatively measure key geometrical parameters of molecular junctions, which helps to achieve precise control of molecular devices

Microscopic Insight into the Activation of O₂ by Au Nanoparticles on ZnO(101) Support

We carry out density functional theory calculations to cast insight on the microscopic mechanism of the activation of O₂ by Au₇ cluster on ZnO(101)-O support. The excellent catalytic activity of Au/ZnO catalyst was ascribed to the distribution of polarized surface charge associated with interface structure. It is found the stoichiometric ZnO(101)-O easily adsorbs and dissociates O₂ to form very stable oxygen-saturated surface. For Au₇ on stoichiometric ZnO(101)-O surface, the two Au atoms neighboring to O could accumulate positive charges, which then upshift the d-band centers toward the Fermi level. These favor the adsorption and dissociation of O₂, providing two Au activation sites. In contrast, for the Au₇ on the oxygen-saturated ZnO(101)-O, all Au atoms become neighboring to O and consequently provide seven activation sites. The workfunction difference between the Au₇ and support induces effective polarized surface charges, substantially promoting O₂ adsorption and dissociation both dynamically and thermodynamically. Further analysis on the effect of different Au positions demonstrates the polarized charge as the microscopic driving force for catalysis. These results would help design of better metal/oxide catalysts by providing important implications for the role of atomic and electronic structures