Primary forests are irreplaceable for sustaining tropical biodiversity

Human-driven land-use changes increasingly threaten biodiversity, particularly in tropical forests where both species diversity and human pressures on natural environments are high. The rapid conversion of tropical forests for agriculture, timber production and other uses has generated vast, human-dominated landscapes with potentially dire consequences for tropical biodiversity. Today, few truly undisturbed tropical forests exist, whereas those degraded by repeated logging and fires, as well as secondary and plantation forests, are rapidly expanding. Here we provide a global assessment of the impact of disturbance and land conversion on biodiversity in tropical forests using a meta-analysis of 138 studies. We analysed 2,220 pairwise comparisons of biodiversity values in primary forests (with little or no human disturbance) and disturbed forests. We found that biodiversity values were substantially lower in degraded forests, but that this varied considerably by geographic region, taxonomic group, ecological metric and disturbance type. Even after partly accounting for confounding colonization and succession effects due to the composition of surrounding habitats, isolation and time since disturbance, we find that most forms of forest degradation have an overwhelmingly detrimental effect on tropical biodiversity. Our results clearly indicate that when it comes to maintaining tropical biodiversity, there is no substitute for primary forests.     

终身大事是说话--谈大学生说话能力的培养

培养大学生的说话能力,教师应尽力改变传统教学模式,大力进行说话教学;学生应注意发展积极心态,主动进行说话锻炼;学校应开展多种多样的锻炼口才的校园文化活动,提供一个相对平等自由的说话环境,从而造就一批批真正文化素质高、能说会道、口才出众的人才。     

Coral communities are regionally enriched along an oceanic biodiversity gradient

Ecological communities are influenced by processes operating at multiple scales. Thus, a better understanding of how broad- as well as local-scale processes affect species diversity and richness is increasingly becoming a central focus in modern community ecology. Here, in a study of unprecedented geographical scope, we show significant regional and local variation in the species richness of coral assemblages across an oceanic biodiversity gradient. The gradient that we sampled extends 10,000 km eastwards from the world's richest coral biodiversity hotspot in the central Indo-Pacific. Local richness and the size of regional species pools decline significantly across 15 islands spanning the gradient. In addition, richness declines across three adjacent habitats (reef slopes, crests and flats). In each habitat, a highly consistent linear relationship between local and regional species richness indicates strong regional enrichment. Thus, even on the most diverse coral reefs in the world, local coral assemblages are profoundly affected by regional-scale processes. Understanding these historical and biogeographical influences is essential for the effective management and preservation of these endangered communities.     

哥德巴赫猜想成不成立均存在反例

本文证明了全序性成不成立均存在反例,许多猜想成不成立均存在反例（为不可证或存在悖论）.如哥德巴赫猜想成不成立均存在反例（为不可证或存在悖论）。奇完全数猜想成不成立均存在反例（为不可证或存在悖论）。