Radiocarbon Dates of Pre-Mankato Events in Eastern and Central North America

1) A group of samples from horizons previously correlated with the upper part of the Cary substage confirms the correlation as reasonable and is consistently related in time to the dates of the peat layer at Two Creeks and subsequent Mankato events. 2) A major glaciation affected the Great Lakes region beginning 25,000 or more yr ago and reaching its maximum extent about 18,000 yr ago. It is represented by drift correlated in Ohio with the Cary substage and, at least in part, with the Tazewell substage; in Illinois and adjacent states it is correlated with most of the Tazewell substage and with the Farmdale loess. 3) The ecology and other associations implied by the dated samples are more consistent with glacial than with nonglacial conditions. 4) The lower till at Sidney, Ohio (W-188), on which is developed a soil considered a correlative of the Fox series soil on gravels and also buried by till of the major glaciation of 25,000 to 18,000 yr ago, indicates an earlier glaciation extensively exposed in Ohio and believed to be an early Wisconsin event. Table 2. List of samples and dates arranged by age groups. See PDF for Table 5) An earlier glaciation, or glaciations, is implied at several localities by peat, gyttja, or wood more than 30,000 yr old, overlain by till. 6) The time interval between the middle group and the old group of samples, which has been determined within conservative radiocarbon limits to be greater than 3000 yr, is possibly of the order of 16,000 yr, as suggested by the depth of leaching at Sidney, Ohio. (The ages of all the samples discussed are listed in Table 2.) 7) An attempt should now be made to fix more closely the dates of the old samples and to reexamine in the field the stratigraphic sequence in the light of the radiocarbon dates discussed.     

闽南山区黄瓜春提早高产栽培技术

总结闽南山区黄瓜春提早高产栽培技术,主要包括选育良种、培育壮苗、适时移栽、加强田管、及时采收等措施,以减少畸形瓜、苦味瓜,提高产量和品质,从而增加经济收入。     

Pleistocene brown bears in the mid-continent of North America

Current biogeographic models hypothesize that brown bears migrated from Asia to the New World ~100 to 50 thousand years ago but did not reach areas south of Beringia until ~13 to 12 thousand years ago, after the opening of a mid-continental ice-free corridor. We report a 26-thousand-year-old brown bear fossil from central Alberta, well south of Beringia. Mitochondrial DNA recovered from the specimen shows that it belongs to the same clade of bears inhabiting southern Canada and the northern United States today and that modern brown bears in this region are probably descended from populations that persisted south of the southern glacial margin during the Last Glacial Maximum.     

Causes of Decadal Climate Variability over the North Pacific and North America

The cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales.     

Status of the Pleistocene Wisconsin Stage in Central North America

A brief review of the history of the Wisconsin Stage in Pleistocene stratigraphy and of research since 1950 shows that post-Sangoman glacial drift older than the Wisconsin drift reported in the older literature is present in central North America. Known and possible stratigraphic positions of the relevant units are shown.     

北美农业收入支持政策的变革

尽管北美自由贸易协定(NAFTA)保留了成员国制定和执行国内农业政策的自主权,但是,近年来,美国、加拿大和墨西哥三国的农业政策在某些方面逐步走到了一起.尤其突出的是农业收入支持政策的一致性趋向,三个国家都削减了对农业生产者的收入支付,制定了反周期计划.     

Reconstructing Farallon plate subduction beneath North America back to the Late Cretaceous

Using an inverse mantle convection model that assimilates seismic structure and plate motions, we reconstruct Farallon plate subduction back to 100 million years ago. Models consistent with stratigraphy constrain the depth dependence of mantle viscosity and buoyancy, requiring that the Farallon slab was flat lying in the Late Cretaceous, consistent with geological reconstructions. The simulation predicts that an extensive zone of shallow-dipping subduction extended beyond the flat-lying slab farther east and north by up to 1000 kilometers. The limited region of flat subduction is consistent with the notion that subduction of an oceanic plateau caused the slab to flatten. The results imply that seismic images of the current mantle provide more constraints on past tectonic events than previously recognized.     

北美大豆食品现状

一、大豆食品在北美的历史大豆在中国有四五千年历史，大约在公元前164年中国发明了豆奶和豆腐。900年后，这些大豆食品加工方法传入日本和太平洋周边国家，大约在1712年大豆进入欧洲、CalVonLinne′给大豆定学名为Glycinemax（意思是带有大根瘤的田野坚果），然而欧洲的土壤和气候条件限制了大豆的生产。1764年大豆传到北美，1年后在佐治亚州种植，随着栽培技术和机械收获技术的发展，大豆作为动物饲料和食用油在北美逐步发展起来。1998／99年度全世界大豆产品超过1.56亿t，85％用于榨油和豆粕，10％用于食品（在美国只有大约1％），5％…     

华北平原棉区--熟棉花栽培技术

华北平原棉花是黄河流域棉区的一个亚区,包括河北省大部、山东全省及河南省的豫北地区。其一熟棉田主要分布于河北黑龙港地区、山东鲁西北地区和滨海盐碱地及河南豫北地区。该棉区一熟棉田普遍的特点是缺水干旱、土壤贫瘠,棉花产量低而不稳、纤维品质较差,应采用综合配套栽培技     

Dietary change and evolution of horses in North America

The evolution of high-crowned molars among horses (Family Equidae) is thought to be an adaptation for abrasive diets associated with the spread of grasslands. The sharpness and relief of the worn cusp apices of teeth (mesowear) are a measure of dietary abrasion. We collected mesowear data for North American Equidae for the past 55.5 million years to test the association of molar height and dietary abrasion. Mesowear trends in horses are reflective of global cooling and associated vegetation changes. There is a strong correlation between mesowear and crown height in horses; however, most horse paleopopulations had highly variable amounts of dietary abrasion, suggesting that selective pressures for crown height may have been weak much of the time. However, instances of higher abrasion were observed in some paleopopulations, suggesting intervals of stronger selection for the evolution of dentitions, including the early Miocene shortly before the first appearance of Equinae, the horse subfamily in which high-crowned dentitions evolved.     

晚近北美森林土壤研究动态

本文综合介绍了北美森林土壤晚近的主要研究方向、苗头、新趋势以及研究方法技术的发展等情况,并与中国森林土壤学研究作了相互比较。     

辽宁省引种班克松的种源选择

对从北美引进的9个种源班克松所做的17a的试验结果表明:班克松是适合辽宁地区的一个优良速生树种,在各个生长时期的生长表现都要好于乡土速生针叶树种———樟子松。班克松不同种源之间的生长状况存在着较大差异,班克松各种源树高、胸径、材积生长在2年生苗期、造林后5年生、8年生、15年生时差异都达到极显著水平。2、8号种源班克松15年生时的生长表现最佳,它们的树高分别比9个种源平均高大4.8%、4.8%,胸径分别比9个种源平均胸径大8.2%、4.9%,材积分别比9个种源平均材积大21.1%、13.5%;而3、5号种源班克松15年生时的生长表现最差。班克松的树高、胸径、材积生长状况与纬度因子呈显著负相关,来自北美北纬46°附近的班克松种源是最适合辽宁地区引种的优良种源,而远离北纬46°及越向高纬度地区的班克松种源在该区表现较差。建议辽宁地区引进北美北纬46°附近的班克松种源,并建立起优良的班克松种子园。     

佛教在北美的传播及其影响

基于中国文化情境,使用跨层次分析方法考量领导情绪劳动对变革型领导和员工组织认同的影响。结果表明：浅层行为与组织认同负相关,深层行为、真实情绪表现分别与组织认同正相关;变革型领导在领导情绪劳动与员工组织认同关系中起部分中介作用;领导成员交换关系在变革型领导与员工组织认同之间起调节作用。因此,企业领导宜调节自己的情绪和塑造自己变革型领导风格,增强员工组织认同感,提升管理效率。     

北美农业合作社发展新动向及其启示王

在对国内外关于北美农业合作社的资料进行系统梳理、总结和分析的基础上,对北美农业合作社发展的新动向、新一代合作社和有限合作组织进行研究。结果表明：北美农业合作社通过一系列组织制度创新,延长了产业链条,增强了市场竞争力;合作社对基本原则进行了修正,允许外部投资者加入,并通过完善相关制度维护了惠顾者的利益。借鉴其经验,我国农民合作社应积极吸纳外部投资者加入合作社,增强合作社竞争力;向产业链下游延伸,提升合作社农产品增值能力;完善合作社的治理结构和盈余分配制度,协调好投资成员与惠顾成员间的关系。     

Model projections of an imminent transition to a more arid climate in southwestern North America

How anthropogenic climate change will affect hydroclimate in the arid regions of southwestern North America has implications for the allocation of water resources and the course of regional development. Here we show that there is a broad consensus among climate models that this region will dry in the 21st century and that the transition to a more arid climate should already be under way. If these models are correct, the levels of aridity of the recent multiyear drought or the Dust Bowl and the 1950s droughts will become the new climatology of the American Southwest within a time frame of years to decades.     

Single-Crystal 40Ar/39Ar Dating of the Eocene-Oligocene Transition in North America

Explanations for the causes of climatic changes and associated faunal and floral extinctions at the close of the Eocene Epoch have long been controversial because of, in part, uncertainties in correlation and dating of global events. New single-crystal laser fusion (SCLF) (40)Ar/(39)Ar dates on tephra from key magnetostratigraphic and fossilbearing sections necessitate significant revision in North American late Paleogene chronology. The Chadronian-Orellan North American Land Mammal "Age" boundary, as a result, is shifted from 32.4 to 34.0 Ma (million years ago), the Orellan-Whitneyan boundary is shifted from 30.8 to 32.0 Ma, and the Whitneyan-Arikareean boundary is now approximately 29.0 Ma. The new dates shift the correlation of Chron C12R from the Chadronian to within the Orellan-Whitneyan interval, the Chadronian becomes late Eocene in age, and the North American Oligocene is restricted to the Orellan, Whitneyan, and early Arikareean. The Eocene-Oligocene boundary, and its associated climate change and extinction events, as a result, correlates with the Chadronian-Orellan boundary, not the Duchesnean-Chadronian boundary.