How forest gaps shaped plant diversity along an elevational gradient in Wolong National Nature Reserve?

Journal of Geographical Sciences - Understanding the underlying ecological processes that control plant diversity within (α-diversity) and among (β-diversity) forest gaps is important for...     

中国生产控制型产业减排的居民福利和区域影响

基于SAM均衡建模方法,建立面向居民福利研究的中国动态多区域社会公平CGE政策模拟模型,对比分析自然情景、生产控制型减排政策情景和最优增长情景下的区域和居民福利变化。研究发现减排政策存在明显的增长率区域分异,这将破坏在自然增长下存在的区域收敛力,导致中国区域之间的差距再度被拉大。面向减排的投资控制政策短期对于居民收入的不利影响较小,但长期影响不容忽视,需要进行居民收入保护。由于城镇退休居民和农村劳动居民已经具备针对性的养老保障政策和“三农政策”保护收入增长,其总体福利受减排政策的冲击较小,因此缺乏相应政策支持的城镇劳动居民应该是收入保护的优先考虑群体。模拟显示减排政策更有利于代际和城乡人均收入差距的缩小,但考虑到减排带来的绝对收入水平下降,不能过于乐观估计这种差距缩小效应。     

Research on temporal and spatial distribution, evolutionary character and mechanism of crustal deformation field before and after the Tangshan earthquake

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Culture,demography and biogeography of sponge science: From past conferences to strategic research?

Perceived changes in the culture of sponge science and sponge conferences served as motivation for an evaluation of the sponge science community and research, over time and at present. Observed changes included a decrease in proceedings publications on sponge fossils and freshwater sponges, sponges from temperate environments, review papers and data syntheses, frequency of aquarium studies, and number of species investigated per publication. Publications on recent sponges, hexactinellids, calcareans, marine, Indo‐Pacific and warm‐water sponges increased, as well as the number of authors per publication and the proportion of field studies. Studies at the level of specimens and ultrastructure were gradually replaced by molecular approaches, but studies at the community level remained stable. The five sub‐disciplines morphology/taxonomy, phylogeny/evolution, physiology, ecology and faunistics also retained about equal proportions over time. Conference publications related to taxonomy, phylogeny and biodiversity prevailed, whereas those on management and conservation were rare, possibly because studies on sponge recovery, survival and mortality were also scarce. The community of sponge scientists has grown and become more diverse over time, presently representing 72 nations. The gender distribution evened out since the first sponge conference and presently favours women at early and men at late career stages. Although stated research interests are generally dominated by physiology and ecology, taxonomy and evolution are favoured after retirement. Sponge science has become more dynamic, but maybe also more competitive and less inclusive. We now face the dual challenge of safeguarding against the loss of some sub‐disciplines, and fostering the collaborative, helpful culture characteristic of sponge science.     

White dwarf + red dwarf binary systems and the period gap of cataclysmic variables

Cataclysmic variables (CV) and pre-cataclysmic binaries (PCB) are discussed. The main difference between them (accretion or its absence) is shown to be a consequence of the evolutionary process and the properties of their progenitors. Both types of system have a bimodal distribution of their periods, but the extrema are in counterphase. Luminosity-effective temperature diagrams for the primary components are used to show that both systems have approximately the same age, which conflicts with the notion of PCBs as precursors of CVs. Calculations of the maximum distance between components for which the system remains stable show that CVs have passed this limit, while PCBs maintain their stability during this evolution. It is suggested that, after ejecting a common shell, future CVs immediately become semi-detached systems. It this is so, then there must be cataclysmic variables which are the central stars of planetary nebulae. __________ Translated from Astrofizika, Vol. 50, No. 3, pp. 427–439 (August 2007).     

On the Lack of Asteroids in the Hecuba Gap

The lack of asteroids in the 2/1-resonance is explained by the global stochasticity of the solutions in the Sun-Jupiter-Saturn-asteroid model. The explanation is based on data obtained with Laskar's frequency map analysis and on simulations showing the decisive influence of Jupiter's orbit perturbations related to the "Great Inequality". This revised version was published online in July 2006 with corrections to the Cover Date.     

鳞毛蕨天山云杉林林冠空隙特征

林冠干扰作为鳞毛蕨(Dryopteris filix-mas (L.) Schott)天山云杉(Picea schrenkiana Fisch. etMey.)林动态自维持的重要因素,在整个林分的动态发展过程中发挥着重要作用。通过对西天山国家级自然保护区内1 hm2典型的鳞毛蕨天山云杉纯林中林冠空隙特征及其形成木和边界木结构的研究,结果表明:在西天山国家级自然保护区实验区46林班内的1 hm2临时标准地中,共调查到17个林冠空隙,林冠空隙干扰返回间隔期为763年。扩展空隙面积在20~280 m2之间变化,冠空隙面积在0~180 m2之间变动。大多数林冠空隙形状变异较大,不同程度地偏离圆形,且均在20~100年之间形成,拥有多株形成木,边界木多由近熟木和成熟木组成。     

2003年北黄海5.1级地震的地震活动特征

对2003年北黄海5．1级地震的地震活动背景、地震序列、震中周围中小地震活动图像及地震学参数等进行了详细分析。认为该次地震为前-主-余型，经历了一个活跃-平静-发震的过程；地震前震中附近出现了孕震空区和一些地震活动性参数异常。     

Numerical study of an oscillating smaller cylinder in the wake of an upstream larger cylinder

A numerical study of flow around two tandem cylinders with unequal diameters was carried out. The upstream larger cylinder was fixed and the downstream smaller cylinder was allowed to oscillate in the transverse direction only. Comparisons of the experimental and numerical results were made to investigate the effects of the gap ratio on the maximum vibration amplitude and vortex shedding frequency. The results showed that the vibration response of the smaller cylinder was significantly affected by the presence of the upstream larger cylinder, and resulted in greatly reduced vibration amplitudes. With an increasing gap ratio, the vibration amplitude increased. However, the magnitude was lower than that corresponding to a single cylinder (with the same diameter as that of the downstream smaller cylinder) under the same flow conditions.     

Species richness,diversity and density of understory vegetation along disturbance gradients in the Himalayan conifer forest

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.