政府决策和管理体制在草地健康发展中的作用

草地资源退化不能仅仅归谬于全球变化、人口压力和放牧强度的增加,政府的决策和现行的体制对草地的健康发展同样起到决定性的作用。如果没有合理的政策法规和有效的实施体制,单纯的技术管理往往不能根本改变目前草地退化的现状。从中国草地管理的发展历程及主要存在问题、草地科研体制与方向对草地生态系统的影响与作用、草地管理的组织机构以及美国草地管理政策启示等几个方面,系统分析了政府决策和体制对草地健康发展的影响,提出了促进草地可持续发展的一系列政策建议。     

Modeling the spatially dynamic distribution of humans in the Oregon (USA) Coast Range

A common approach to land use change analyses in multidisciplinary landscape-level studies is to delineate discrete forest and non-forest or urban and non-urban land use categories to serve as inputs into sets of integrated sub-models describing socioeconomic and ecological processes. Such discrete land use categories, however, may be inappropriate when the socioeconomic and ecological processes under study are sensitive to a range of human habitation. In this paper, we characterize the spatial dynamic distribution of humans throughout the forest landscape of western Oregon (USA). We develop an empirical model describing the spatial distribution and rate of change in historic building densities as a function of a gravity index of development pressure, existing building densities, slope, elevation, and existing land use zoning. We use the empirical model to project changes in building densities that are applied to a 1995 base map of building density to describe future spatial distributions of buildings over time. The projected building density maps serve as inputs into a multidisciplinary landscape-level analysis of socioeconomic and ecological processes in Oregon's Coast Range Mountains. This revised version was published online in July 2006 with corrections to the Cover Date.     

中美农产品质量安全检验检测体系比较研究

通过对中美农产品质量安全管理体制、检测机构组成和布局、检测机构管理机制以及运行情况等方面的比较研究,分析了我国农产品检验检测体系存在的差距,并在此基础上提出完善我国农产品质量安全检验检测体系的建议。     

美国金门公园漫游

金门公园位于美国西部加利福尼亚州三藩市的西部太平洋海岸,属地中海型温暖气候。曾于1894年举办世界博览会,现今已成为三藩市一块可供玩乐、休闲、陶冶身心和市民求知识的好地方。主要活动景点有:植物园,日本庭园,温室花园;加州科学院内的天文馆、水族馆、热带雨林馆和自然历史博物馆;世博会遗迹迪杨艺术纪念博物馆及一些具有历史意义的建筑物;还有众多提供娱乐、体育活动场所。     

美国的城市林业概念及管理

1 美国的城市林业概念体系 1．1 城市森林的定义与特点 城市森林可以定义为：分布在密集人口聚居区的树木和相关植被的综合,在空间上既包括城乡结合部的乡村,也包括城市建成区域。Clegg在研究美国城市森林时认为,城市森林不仅包括行道树、也包括停车点、校园、城市公园、河岸边、墓地以及自由通道的交叉处的树木,既包括了人工精细护理的矮灌木,也包括城市郊区街道的天然乔木。     

Behavior as a tool for assessing a managed landscape: a case study of the Karner blue butterfly

In an increasingly human-dominated landscape, effective management of disturbance-maintained ecosystems, such as grasslands and savannas, is critical to the conservation of biodiversity. Yet, the response of individual organisms to landscapes created by disturbances and management is rarely studied. In this study, we examined the endangered Karner blue butterfly, Lycaeides melissa samuelis, in a heterogeneous oak savanna. Our objective was to quantify the butterfly’s habitat use and behavior to assess the effects of prescribed burning. The oak savanna management in Ohio, USA divides each Karner blue site (n = 4) into three units. Each one-third unit is then burned, mowed, or unmanaged in an annual rotation within each site, and the result is a fire return interval of ~3 years. Our surveys measured habitat use, while behavior observations quantified reproduction and foraging for the two annual broods. Our habitat use results showed burned treatments were recolonized quickly, but there was not a clear selection for burned treatments. Foraging rates were similar in all treatments; however, females oviposited significantly less in unmanaged treatments (only 5 of 127 ovipositions). This oviposition preference was likely due to habitat degradation and the availability of recently burned, early successional habitat. Since Karner blues avoided reproduction in units unburned for ≥4 years, these units could be burned to create high quality early successional habitat. These results demonstrate how behavioral decisions can be pivotal forces driving spatial population dynamics. Our case study demonstrates how a fine-scale landscape perspective combined with measurements of behavioral processes can assist with management decision-making.     

美国大豆生产、科研、推广和市场体系(续六)

(接续五)在美国,如果一笔现货交易在期货市场上没有相应的保值头寸,银行可能拒绝向其提供购买现货的贷款,所以农业合作社与农民之间都会遵守诚信,加之农民又是合作社的股东,彼此有长期的合作关系,所以在上述市场运作过程中很少出现违约事件.     

美国大盐湖卤虫业情况及我国卤虫产业状况

本文介绍了美国大盐湖卤虫业情况,同时介绍了我国卤虫卵生产状况,并就国内卤虫生产情况和国际形势提出了看法。     

美国农业政策演变阶段、趋势和启示

美国作为世界上最大的农业生产和贸易国,其农业政策对世界农产品市场有重要影响。梳理了美国农业政策演变阶段,展望了其未来趋势和对中国农业政策的启示,并根据美国农业政策主要内容的差异,可将其演变分为四个阶段;未来美国农业政策将更加注重完善农业保险补贴政策,重视保护资源和环境,农业政策将逐渐由"黄箱"向"绿箱"政策转变。对于中国来说,应借鉴美国农业政策的一些措施,如从法制高度完善中国农业政策体系,根据社会经济和国际农业规则的发展变化调整农业政策,农业政策的制定要秉承"以人为本"和可持续发展的理念。     

Key factors influencing transport of white shrimp (Litopenaeus setiferus) post-larvae into the Ossabaw Sound system, Georgia, USA

We examined conditions under which white shrimp (Litopenaeus setiferus) post‐larvae enter an estuarine channel receiving high freshwater discharge and one receiving negligible discharge in the Ossabaw Sound system of Georgia, USA, during 1997 and 1998. We used surface nets to collect plankton over several 14‐day periods, during which consecutive tows were made at night against the flooding current at stations in the inlet channels. During these sampling periods, additional intensive periods of around‐the‐clock surface and near‐bottom (using a bottom sled) plankton tows were made. Data on oceanographic conditions were obtained from moored instrument arrays and shipboard sampling. We identified three key factors that influenced the densities of post‐larval white shrimp in time and space within the Ossabaw inlet system. The first factor was a critical minimum temperature of coastal waters of 27–28°C. Once the threshold temperature was reached, lunar tidal stage became a key factor when the full duration of the flood tide coincided with darkness during peak ingress. This peak also coincided with an increase in water level within the system by more than 0.2 m, which induced an additional influx of water that reinforces the flood current over the ingress period. Our results suggest that the direction of subtidal currents (into or out of the system) becomes a significant factor in post‐larval ingress when influx of water coincides with the time of favorable temperature conditions and nighttime flood tides.