Nutrient addition and disturbance effects on the community composition and assembly in a desert steppe北大核心CSCD

The effects of short-term nutrient additions (NPKμ, 10 g·m- 2) and disturbances on the species diversity, functional traits, soil properties, and community assembly mechanisms of the herbaceous community in the Urat desert steppe were examined. A mixed linear model, principal component analysis, and null model methods were utilized and both disturbance and interaction treatments were found to significantly reduce species richness and β diversity. Short-term nutrient additions significantly reduced soil pH but increased soil electrical conductivity. Six functional traits of the dominant species (i.e. Stipa glareosa, Peganum harmala, Salsola collina, Corispermum mongolicum) and six community-weighted mean significant changes under the disturbance and nutrient addition treatments were identified. The disturbance and nutrient additions promoted the transformation of the dominant species in the community from conservative strategies to acquisitive strategies. The results of the two null models revealed that community assembly under the control tended to be a stochastic process, while the disturbance and interaction treatments tended to be deterministic processes, and that of the nutrient addition treatments tended to be weaker deterministic processes. Plant communities in the desert steppe responded and adapted to the nutrient additions and disturbances through changes in the dominant species and their crucial functional traits. © 2023 Chinese Academy of Sciences. All rights reserved.     

放牧和模拟降水对短花针茅荒漠草原植物功能群多样性的影响

为探究放牧和降水变化对植物功能群的影响,本文以内蒙古短花针茅(Stipa breviflora)荒漠草原为研究对象,开展了野外控制试验。试验设置围封和适度放牧,分别进行模拟降水处理(减少降水量50%、自然降水、增加降水量50%、增加降水量100%),并在每年8月观测植物群落组成。结果表明：减水会降低植物功能群多样性、生物量和物种数量,增水有利于植物功能群多样性的提高。多年生丛生禾草多样性随降水量的增加而升高。同时,对降水梯度和功能群多样性进行拟合分析发现,降水量低于年降水量16%则不利于除灌木、半灌木外其他功能群植物的生长。围封草地增水67%～79%时,功能群的Simpson指数、Shannon-Wiener指数、Pielou指数值均较高,功能群多样性较高;由于放牧提高了植物的水分利用效率,放牧地各指数在增水26%～50%时较高,功能群多样性较高。综上,适度的放牧及水分补充有利于提高植物功能群多样性。     

红酵母的性质及其应用研究

红酵母是酵母菌的一个属,腐生,分布广泛,在医学、食品、化工和农业等方面都有一定的应用,但目前并没有引起人们足够的重视。综述了红酵母的种属特性、理化特性、培养及其应用。     

Flexure-torsion Analysis of Variable-curvature-box Girder Considering Non-coincidence of Torsion Center and Gravity Center

In order to consider the effect of non-coincidence of torsion center and gravity center,the rectangular variable-curvature-box girder with vertical symmetrical axis is studied. Considering the influence of shear deflection and non-coincidence of torsion center and gravity center, the elastic equilibrium formulas are established. Based on deformation equations of the girder and the relations of inner forces and deformations,the flexure-torsion differential equations are developed. The equilibrium differential equations and Galerkin methods formulas for clothoid curved box girder are presented.     

Case- carburization Numerical Modeling and Craft Optimization on Steel Parts of Various Shapes

According to the diffusion equation of carburizing process and its boundary conditionand initial condition, various shapes steel parts are modeled under various case carburize craft parameters, concentration distribution curves have been obtained. Various craft parameters are compared, and carburizing temperature has more influence on carbon concentration distribution. Various shapes steel parts' carbon concentration distribution curves have some difference. According to the carbon concentration distribution curve, craft parameters can be adjusted in order to obtain the best carburizing craft.     

Density Functional Theory Compute on Electronegativities to Superconductivity of Oxides

In this article we have worked out the correlation between electronegativity and high temperature superconductivity for oxide. It is suggested the equalized electronegativity, X cq , can be used as a empirical criterion for superconductivities of oxides. For determining the X cq , a new formula for the calculation of X cq values has been obtained The X cq values of 230 oxide superconductors have been calculated. The result shows that the X cq values of all the oxide superconductors concentrate in a narrow range from 5.00 to 5.63 and that the oxides with values out side this region would be non-superconductive. This criterion can be applied to almost all the oxide superconductors. It is clearly that this result is able to benefit further inquiries about the mechanism of superconductivity.     

The Multiple Solutions for a Class of Quasilinear Elliptic Equations

A three critical point theorem is proved. As its applications, Dirichlet problem for a class of quasilinear elliptic equations cf second order is considered.     

Research on Mapping Method of Customer Need Information in Product Family Improvement

Aiming at ensuring that product family improvement is based on customer needs while taking full advantage of enterprise history database, firstly, customer needs in the product family improvement are expressed. Then a method of realizing the mapping of customer needs to functional requirements is presented, which is based on quality function development and association rule mining. Finally, an example illustrates the good application of the method.     

THE BASIC PROPERTIES OF CONDITIONAL EQUATION WITH ACCUMULATIVE STATE

Several aspects of the conditional equation derived from the accumulative equation are discussed in detail. The results indicate that the conditional equation not only is well consistent with the principles of electronegativity and absolute hardness equalization, but also satisfies the bonding of a full -prerequisite condition, e. g. two like electronic charge species repel and unlike attract each other'. In addition these principles are in the accumulative state. Mathematically, some other aspects of the conditional equation are worth studying based on the generalization of this equation.