ENSO classification indices and summer crop yields in the Southeastern USA

This research uses a quantitative methodology for directly comparing the responses of observed crop yields in the SE USA to ENSO phenomena classified using dissimilar ENSO indices. ENSO condition has been related to agricultural yields in many parts of the world. It has been generally recognized that the strongest effects on spring and summer crops occur during the boreal winter, and therefore most directly affect spring-summer field crops in the southern hemisphere. However, some ENSO effects on northern hemisphere spring and summer crops have been found, particularly when researchers have used sub-annual indicators of ENSO conditions that, unlike annual ENSO indices, distinguish between continuity and change prior to or during the crop season. To evaluate the utility of such sub-annual ENSO indicators for agriculture in the SE USA, a tercile-based scoring system was devised to compare four distinct ENSO indices: three monthly ENSO indices and the JMA annual ENSO index. Each index was scored in its ability to predict crop yields differing from the historically normal tercile for corn (Zea mays L.), cotton (Gossypiumhirsutum L.), and peanut (Arachis hypogaea L.). Annual crop yield data were used from selected counties in five Southeastern USA states. No geographic differentiation among the data was included in the analysis. This aggregation of county data increased the sample size for each crop, to address the limitation of a short time-series (47 years) distributed among up to 9 ENSO categories. Statistical significance was compared using contingency tables and the Fisher exact test. Peanut and corn yield response matched best to the Multivariate ENSO Index (MEI) and cotton, to the Oceanic Niño Index (ONI). The MEI and ONI are quantitative indices, while the lower-scoring JMA and Modified-JMA indices are categorical. Therefore, future efforts may reduce the focus on categorical (Niño, Niña, Neutral) classification, and explore the response of crop yields to quantitative ENSO data.     

SOIL SALINITY AND SODICITY APPRAISAL BY ELECTROMAGNETIC INDUCTION IN SOILS IRRIGATED TO GROW COTTON

In the Far West Texas region in the USA, long‐term irrigation of fine‐textured valley soils with saline Rio Grande River water has led to soil salinity and sodicity problems. Soil salinity [measured by saturated paste electrical conductivity (EC_e)] and sodicity [measured by sodium adsorption ratio (SAR)] in the irrigated areas have resulted in poor growing conditions, reduced crop yields, and declining farm profitability. Understanding the spatial distribution of EC_e and SAR within the affected areas is necessary for developing management practices. Conventional methods of assessing EC_e and SAR distribution at a high spatial resolution are expensive and time consuming. This study evaluated the accuracy of electromagnetic induction (EMI), which measures apparent electrical conductivity (EC_a), to delineate EC_e and SAR distribution in two cotton fields located in the Hudspeth and El Paso Counties of Texas, USA. Calibration equations for converting EC_a into EC_e and SAR were derived using the multiple linear regression (MLR) model included in the EC_e Sampling Assessment and Prediction program package developed by the US Salinity Laboratory. Correlations between EC_a and soil variables (clay content, EC_e, SAR) were highly significant (p ≤ 0·05). This was further confirmed by significant (p ≤ 0·05) MLRs used for estimating EC_e and SAR. The EC_e and SAR determined by EC_a closely matched the measured EC_e and SAR values of the study site soils, which ranged from 0·47 to 9·87 dS m⁻¹ and 2·27 to 27·4 mmol^1/2 L^−1/2, respectively. High R² values between estimated and measured soil EC_e and SAR values validated the MLR model results. Results of this study indicated that the EMI method can be used for rapid and accurate delineation of salinity and sodicity distribution within the affected area. Copyright © 2012 John Wiley & Sons, Ltd.     

对美国渔业管理模式的初步探讨

美国的渔业法规体系经过几十年的制定和修订已趋完善。目前的管理现状首先是重视立法和执法，并实现了由生产型向管理型、由对资源和一半的管理转为对人的管理，并用科研指导管理，设立渔区管理理事会，发挥群众的管理作用。与美国的管理模式相比， 中国首先应该改善管理体制、加强科研投入、建立渔民协会发挥群众的管理作用。试图通过探讨美国的渔业管理模式，和我国目前所应用的渔业管理进行对比分析，从中找出可供我国学习并借鉴的方面，并得出一些初步的设想与建议，以供有关渔业管理部门参考。     

Crop yield and rooting as affected by fragipan depth in loess soils in the southeast USA

The combination of soil erosion and restrictive subsurface features can adversely influence root growth and crop productivity. The effects of depth to a restrictive layer on yield and root development were determined for soybean (Glycine max (L.) Merr.) and corn (Zea mays L.) grown on Grenada silt loam (Oxyaquic Fraglossudalfs) in West Tennessee. Seven sites were selected in a cropped field where depth to the fragipan ranged from 0 to 107 cm below the soil surface. Across-the-site comparisons involving bulk density, soil color, exchangeable acidity and organic carbon indicated that at the sites that were shallow to the fragipan, profile modification had occurred as a result of soil erosion. Soils were sampled to 120 cm depths in 15 cm increments within the row and 25 and 51 cm from the row. Roots were extracted and total root lengths were determined by the line-intercept method. Greater total root lengths were observed with increasing depth to the fragipan. Crop yields decreased significantly as depth to the fragipan decreased. Soybean yields ranged from 0.5 Mg ha⁻¹ on the 0 cm depth site to 2.8 Mg ha⁻¹ on the 107 cm depth site, whereas corn yields ranged from 5.5 Mg ha⁻¹ on the 0 cm depth site to 10.0 Mg ha⁻¹ on the 107 cm depth site. Erosion was not measured directly; however, the reduced soil depth due to erosion caused an easily demonstrated reduction in root growth and yield in both corn and soybean.     

美国教育理念的考察与启示

考察在高等教育普及化条件下,美国高校培养教育学生的理念,对大多数美国大学来说,教育理念就是培养能适应社会需要的、毕业后能尽快就业的学生;把国家利益至上和市场经济所要求的核心价值观的教育置于十分重要的位置;以培养创新型人才为坚定不移的目标;以法治、诚信为基础的价值观教育更注重行为教育。这些理念对走向高等教育普及化的我国高校有积极的启示作用：（1）尽快完善教育法律法规体系;（2）地方高校要提高为地方发展的自觉性;（3）高度重视思想道德的教育。     

美国有毒植物概述及其对畜牧业生产的影响

有毒植物在世界范围内影响着畜牧业发展和人类生活,甚至在有些地区特别是牧区草地发生严重的动物毒草中毒灾害,引起动物大批中毒死亡,给草地畜牧业生产造成重大损失,动摇了牧民对草地的安全感。美国等世界发达国家在有毒植物的生物学、生态学、毒理学、中毒病控制和综合利用研究方面起步早,已经取得一定成果。中国在有毒植物研究方面起步较晚,与美国等发达国家有很大差距,尤其是在有毒植物中毒病控制和综合利用方面。本文从美国有毒植物研究历史及现状、地理环境与有毒植物分布概况、有毒植物对畜牧业造成的灾害、有毒植物种类及主要有毒植物、有毒植物防治策略等方面做了简要论述。     

美国森林风景管理系统及其借鉴与应用

借鉴国际森林风景管理系统构建和应用实践,是提高中国森林风景资源管理水平、更好地满足公众对森林游憩需求的重要途径之一。文中概述了美国森林风景管理系统的发展历程、结构内容、特点、应用状况和发展趋势。该系统以科研成果和近40年的实践经验为依据,主要包括调查分析、规划设计、方案实施、监测评估4个步骤,强调融入生态系系统管理思想和公众参与,将在生态美学、城郊风景、场所感、动态管理、可视化和视觉模拟等方面不断优化发展。我国森林风景资源管理的观念、理论和技术基本处于初步发展阶段。从中国实际出发、积极吸收国际先进技术和管理理念、加快中国森林风景资源管理系统研发步伐,对于提高我国森林风景资源管理水平具有重要现实意义。     

美国国有林经营及对中国的启示

在介绍美国国有林经营政策的基础上, 针对中国国有林经营现状, 提出应借鉴的经验:减轻税费负担, 加强营造林基础; 提高林业科技水平, 发展高效林业; 构建国有林资源法制化管理体系; 重视跨部门跨学科的交流和合作; 采用生态系统管理方法, 开发和保护并重。     

美国高等教育模式对英国高等教育大众化的影响探析

作为率先实现高等教育大众化的成功典范,美国的高等教育模式在英国得以广泛传播并被关注、争议和借鉴。探析英国高等教育由精英型向大众型的转化过程,从理念、政策到实践,从数量扩张、结构调整到制度创新,其发展路径中均可见到美国影响的痕迹。透视其影响机制,可以为我国高等教育大众化的健康发展提供有益的借鉴。     

美国高尔夫球场狗牙根草坪杂草防除研究进展

根据文献报道,介绍了美国高尔夫球场狗牙根草坪杂草防除地进展,狗牙根草坪杂草防除的难点是禾本科杂草。用甲胂钠,阿特拉津或西玛津防除鼠尾粟,用费赛特及费赛特加灭草喹防除铺地黍,用甲胂钠及ｄｉｔｈｉｏｐｙｒ除草通,恶草灵,圃草定,黄草消防防马唐,用禾草灵,圃草定ｄｉｔｈｉｏｐｙｒ,除草通,恶草灵防除牛筋草;用灭草喹防除野草,供试狗牙根草坪品种为普通狗牙根,Ｔｉｆｗａｙ和Ｏｒｍｏｎｄ。还介绍了禾草灵,西玛