Zircon ages of felsic volcanic rocks in the upper precambrian of the blue ridge, appalachian mountains

Five Zirconi samples from Pennsylvania, Virginia, and North Carolina yield discordant uranium-lead ages which suggest an original age of 820 million years and an episodic lead loss at 240 million years. The indicated age of lead loss is interpreted as the age of movement of the Blue Ridge thrust sheet.     

Pleistocene glaciation on st. George, pribilof islands

A small ice cap (covering about 12 square kilometers) and at least two-probably four-cirque glaciers (each covering less than 1 square kilometer) occurred on St. George Island, Pribilof Islands, probably during the Illinoian; Glaciation. Snowbanks persisted during a later cold cycle, probably during the Wisconsin Glaciation, with no glaciers existing. We found no evidence of glaciation on other Pribilof islands.     

Iceberg discharges into the north atlantic on millennial time scales during the last glaciation

High-resolution studies of North Atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years, much more frequently than the 7000-to 10,000-year pacing of massive ice discharges associated with Heinrich events. The calving cycles correlate with warm-cold oscillations, called Dansgaard-Oeschger events, in Greenland ice cores. Each cycle records synchronous discharges of ice from different sources, and the cycles are decoupled from sea-surface temperatures. These findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above Greenland and in calving from more than one ice sheet.     

河北省退化山场土壤系统熵研究

根据耗散结构理论，提出用土壤系统熵来表征退化山场土壤的退化程度，并对退化山场土壤及化肥培肥后的土壤系统熵值进行了计算。提出向退化山场土壤生态系统中引入负熵流是改良土壤，使退化山场土壤生态系统稳定有序的必要条件。     

Control of methane sediment-water bubble transport by macroinfaunal irrigation in cape lookout bight, north Carolina

Methane transport by bubble ebullition through bubble tubes from sediments to overlying waters in Cape Lookout Bight, Outer Banks of North Carolina, occurs only in the absence of burrowing macroinfauna, which indirectly prevent saturation methane concentrations by irrigating surface sediments with dissolved sulfate. Distribution of macroinfauna in the bight is limited to bottom areas not subjected to periodic anoxic conditions.     

Sea-level lowering during the illinoian glaciation: evidence from a bahama "blue hole"

Stalagmites have been recovered from 45 meters below sea level in an underwater karstic cave ("blue hole") near Andros Island in the Bahamas. Uranium series ages, corrected for contamination of the sample by young marine carbonate replacements, show that the speleothem was deposited between 160,000 and 139,000 years before the present. This period corresponds to the Illinoian glacial event and demonstrates that sea level must have been lowered by at least 42 meters (allowing for subsidence) from its present position during this time.     

发展黑龙江省北部地区亚麻生产的几点建议

近年农业连续丰收，加之农产品加工能力滞后，导致粮价下跌，农民种粮效益下滑。但从1998年起国内外亚麻市场渐趋活跃，亚麻产品价格平稳回升，去年省内农户种亚麻纯收入2 000元/hm2左右，就地雨露加工出售纤维纯收入3 000元/hm2以上，直接经济效益的趋动，农民种麻积极性空前高涨，为发展亚麻种植业带来新机遇。     

云南省高黎贡山土壤线虫群落结构及多样性

对云南省高黎贡山国家自然保护区不同海拔高度0～10,11～20,21～30 cm土层土壤线虫群落进行调查,共获得线虫2纲9目28科79属,其中基齿属Iotonchus和孔咽属Aporcelaimus为优势属,捕食/杂食类群为主要营养类群,占60.01%.相关性和显著性方差分析表明,土壤全N含量与线虫密度呈显著正相关(F=0.628, p=0.038).不同海拔高度线虫群落结构比较稳定,在海拔2 021 m的中山湿性常绿阔叶林中线虫类群和个体数最丰富,然后向高、低海拔逐渐递减.成熟指数值表明,高黎贡山土壤线虫群落结构较稳定;线虫通路比值(NCR ) 计算表明,土壤有机质主要依靠真菌分解途径;Shannon-Wiener多样性指数(H′)、Simpson优势度(D)和多群落间比较多样性指数(DIC )在低海拔的灌丛林与半湿润常绿阔叶林和中山湿性阔叶林有显著差异.     

桂西南喀斯特山地木本植物群落种间关系及CCA排序

基于桂西南喀斯特山地木本植物群落11个样方(20 m×20 m)取样调查,运用生态位理论、种间关系原理、双向指示种分析(TWINSPAN)和典范对应分析(CCA)方法,探讨主要木本植物间的种间联结性和相关性及其与环境因子之间的关系。结果表明:桂西南喀斯特山地木本植物群落中麻栎、枫香、蚬木占优势地位,罗伞树-鹅掌柴、九节-琴叶榕、澄广花-鱼骨木的生态位重叠度分别在3种木本植物群落中最大。麻栎次生林群落总体种间关系表现为不显著正关联,χ2检验统计显示正关联种对数有50对,负关联种对数有52对,无关联种对数有3对,正负关联比为0.96,检验显著率为6.67%。枫香次生林群落总体种间关系表现为不显著负关联,χ2检验统计显示正关联种对数有96对,负关联种对数有113对,无关联种对数有1对,正负关联比为0.85,检验显著率为8.10%。蚬木次生林群落总体种间关系表现为显著正关联,正关联种对数有19对,负关联种对数有17对,正负关联比为1.12,检验显著率为8.33%。CCA前瞻选择显示土壤pH值、全磷、坡向、土壤全钾、海拔是影响桂西南喀斯特山地木本植物群落物种组成与分布最重要的因子,总体上可以对76.95%的环境因子进行解释。物种间的正联结性越显著,其生态位重叠程度越高,反之,物种间的负联结性越显著,其生态位重叠程度则越低。      

豫北地区桃蛀螟发生规律及综合治理技术

桃蛀螟(Dichocrocis punctiferalisGuenee)又名桃蠹螟、桃斑蛀螟,俗称蛀心虫、食心虫,在我国分布极广。以幼虫蛀食桃果,使果实不能发育,常变色脱落或果内充满虫粪,不可食用,对产量和质量影响很大,群众常用“十桃九蛀”反应此虫对桃果危害的严重性[1]。其寄主植物除桃外还能危害     

豫北平原土壤养分与施肥状况探析

为摸清豫北平原土壤养分状况、合理利用土壤资源和指导科学施肥,利用全球卫星定位系统(GPS)准确定位,在豫北平原进行网格取样(20km×20km),同时进行农业生产状况和农民施肥习惯调查.土壤样品分析结果表明:豫北平原土壤养分状况整体处于中等水平,土壤有机质、碱解氮,速效磷和速效钾平均含量分别为1.43%,65.38mg/kg、17.7mg/kg和74.23mg/kg.与第二次土壤普查结果相比土壤养分含量有明显变化,土壤有机质、土壤速效磷含量显著提高,而土壤碱解氮、土壤速效钾含量下降.施肥调查表明:90%以上农户采用秸秆还田,重视施用氮、磷肥,而忽视施钾肥,存在所施肥料养分单一、养分配比、施肥方式不合理等问题.豫北平原应重视有机肥施用、推广秸秆还田,注意减少磷肥用量、注重补施钾肥,采用复合和缓/控释氮肥及合理的施氮技术.政府和农业科技部门应重视宣传和加大平衡施肥技术的推广.     

Prehistoric rock avalanches in the olympic mountains, washington

Rock avalanches blocked streams in the Olympic Mountains southwest of Puget Sound during the past few thousand years. Limiting radiocarbon ages indicated that three or four of six avalanches occurred from 1000 to 1300 years ago or shortly thereafter. Most of the dates were from the outer preserved rings of trees drowned behind avalanche dams. These three or four avalanches may be coeval not only with one another but also with abrupt tectonic deformation in western Washington. No rock avalanches in the Olympic Mountains are known to have resulted from storms or earthquakes during the past century. The avalanches strengthen the case that a large prehistoric earthquake occurred in the Puget Sound region.     

湘南地区茄子嫁接丰产栽培技术

湘南地区茄子种植面积逐年扩大,茄子土传病害日趋严重,产量和品质受到较大影响,采用抗病砧木与当地主栽品种嫁接,可延长茄子采收期,大幅度提高产量。     

豫南鄂北地区果蔬玉米品种引进 筛选与评价

通过对多个果蔬玉米品种的引进试种 ,筛选出 8个在豫南、鄂北地区表现型较好的鲜食果蔬玉米品种 ;结果表明 ,五彩甜玉米、紫玉糯、美国黑玉米 (黑珍珠 )等三个品种在播期安排、抗逆性、适口性、外观商品性等综合性状上优于其它品种 ,可做为两地区的不同果蔬玉米的首选品种     

基于主成分分析的粤北山区土地生态安全评价

为评价研究粤北山区土地生态安全现状,选用主成分分析方法,从资源环境压力、土地利用状态和社会经济发展等方面选取了14个指标,以县域行政区划为评价单元构建评价指标体系,对粤北山区土地生态安全进行综合评价。结果表明,粤北山区土地生态安全综合得分为0.477 9,整体处于第Ⅲ级临界安全水平,土地生态安全等级在空间分布上呈西高东低的区域差异;人口密度和经济发展水平是影响粤北山区土地生态安全的主要因素,与土地生态安全等级呈负相关关系。     

不同资本匮乏型农户的风险应对策略——以陕南秦巴山区为例

为探究不同资本匮乏型农户在面临不同生计风险冲击时如何应对,以陕南秦巴山区414份农户调查数据为例,在判断农户生计资本类型并测算生计风险的基础上,采用有效性评价和Logistic回归分析方法,对农户风险应对策略的影响因素进行了研究。结果表明:不同类型农户偏好的风险应对策略组合不同;并且,“社会保险及社会救济”与“改进生产技术”的策略有效性评价较好,综合评价值分别为2.41、2.39;生计风险-生计资本类型的交互项对农户风险应对策略影响显著,且不同生计资本类型、不同抗风险能力的交互效应存在差异。因此,为实现农户稳定脱贫、巩固脱贫攻坚成果,应结合农户自身生计资本类型及外部生计风险,制定差异化的扶贫措施以实现防风险与强生计相结合的稳定脱贫战略。     

粤北地区模拟酸雨对油菜部分品质的影响

粤北地区酸雨频发,为了对粤北地区油菜种植提供指导建议,我们以花油8号、华杂62、华协102三个品种为试验材料,在温室条件下,通过区间试验的方法,模拟粤北地区酸雨发生情况,以foss-3700近红外品质分析仪试验样品检测工具,展开了酸雨对油菜品质的影响研究。结果表明,模拟酸雨对油菜品质,包括硫甙含量、芥酸含量、含油量、蛋白质含量、油酸含量等影响不显著。     

The history and survival of traditional heirloom vegetable varieties in the southern Appalachian Mountains of western North Carolina

Southern Appalachia is unique among agroecological regions of the American South because of the diverse environmental conditions caused by its mountain ecology, the geographic and commercial isolation of the region, and the relative cultural autonomy of the people that live there. Those three criteria, combined with a rich agricultural history and the continuance of the homegardening tradition, make southern Appalachia an area of relatively high crop biodiversity in America. This study investigated the history and survival of traditional heirloom vegetable crops in western North Carolina and documented 134 heirloom varieties that were still being grown. I conducted interviews with 26 individuals from 12 counties in western North Carolina. I used a snowball sampling method to identify individuals or communities that maintained heirloom vegetable varieties, and used the “memory banking” of farmers’ knowledge as a strategy to complement the gathering of seed specimens. Most of the varieties were grown and saved by homegardeners; beans were the most numerous. Results indicate that usually only one or two individuals in a community maintained significant numbers of heirloom varieties and that many communities have lost their heirloom vegetable heritage altogether. The decline of the farming population combined with a lack of cultural continuance in family seed-saving traditions threatens the ability of communities to maintain crop biodiversity. Some of the cultivars may represent the last (small) populations of endangered varieties.

Geophysics from triton to the deep blue sea: new quake forecast: north by northwest

Geophysics is closing out the 1980s with a bang. October's Loma Prieta earthquake grabbed the spotlight at this month's American Geophysical Union's annual fall meeting in, of all places, San Francisco; the quake also closed down one of the official hotels, depriving hundreds of the 4500 attendees of rooms. Other hot topics of the late 1980s-Voyager's tour of the outer solar system and the greenhouse effect-got their share of attention as well.