漓江上游土地利用与覆盖变化及其驱动力研究

漓江上游是漓江流域主要的水源林区域,也是漓江风景名胜区重要的生态安全屏障。借助Arc GIS和ENVI软件,对2002年和2013年两期遥感影像数据进行解译,结合土地利用和覆盖研究方法,分析了漓江流域上游土地利用类型结构的变化以及土地变化的人文驱动因子。研究表明:2002~2013年漓江上游土地利用结构稳定,生态环境保持良好。在整体结构中,土地利用类型主要以林地和耕地为主。土地利用和覆盖变化呈现林地、耕地减少,草地、湿地和人工表面增加的趋势。在短时间尺度上,人类的社会经济活动是漓江流域土地利用/覆盖变化最主要的驱动因素。     

疏勒河中下游绿洲土地利用变化及其驱动力分析

通过1990、2000、2005和2010年4期遥感影像解译结果,获取了近20年来疏勒河流域中下游绿洲的土地利用变化数据,进一步利用土地利用动态变化模型,对疏勒河流域中下游绿洲土地利用变化过程、趋势及其驱动机制进行了深入分析。结果表明:近20年来疏勒河流域中下游绿洲土地利用类型仍以草地、水域和耕地为主,土地利用整体特征未发生显著改变,但不同土地利用类型的变化差异较大;其中,研究期内耕地呈持续高速增长态势,草地出现较大的波状起伏,水域面积于2000年后持续减少;1990—2005年草地和水域面积减少引起绿洲缓慢萎缩,2005—2010年草地和耕地面积增大导致绿洲缓慢扩张;人口、政策方向、城市化程度和技术水平等人文因子是绿洲变化的主要驱动力。     

土地利用时空变化及其驱动因子分析——以宁波市鄞州区为例

进入21世纪,土地利用/土地覆盖变化(LUCC)成为重点研究领域。文章通过Arcgis软件支持对鄞州共7年的土地利用的土地利用动态度,地类之间的转换方向以及土地利用时空变化等三方面进行分析,并对主要地类变化的驱动力因子进行了量化分析。研究结果表明:(1)鄞州区土地利用呈现高速、复杂的变化;(2)耕地呈现出高度的单向不平衡转移,转移方向呈多方向性;(3)建设用地空间变化最大,呈现出了不可逆的高度扩张性;(4)总人口的增长,工业的发展,国内生产总值和财政收入的增加是鄞州建设用地扩张的主要驱动因子;人口的增长,特别是非农业人口的增长日益成为鄞州耕地变化的主要驱动因素。     

土地利用／土地覆盖变化与土地利用规划——以安徽马鞍山市为例

利用马鞍山市1983、1996、2010年的土地详查、土地现状和土地规划数据,分析了马鞍山市1983—1996年以及1997-2010规划年土地利用类型结构的变化及其土地变化的驱动因子。通过相关分析揭示出：马鞍山市1983年以来土地利用／土地覆盖变化主要表现为耕地减少和建设用地的增加,耕地减少的主要驱动因子是人口增加、工业和农业的发展;规划期土地利用／土地覆盖变化的驱动因子是土地管理、人口和社会经济的发展;新的土地管理法的严格施行,将使今后我国区域土地利用／土地覆盖变化不同程度的向着有利于经济、社会和生态环境的方向发展。     

山东半岛北部海岸带土地利用变化与驱动力——以龙口市为例

海岸带土地利用/覆盖变化是“海岸带陆-海相互作用计划“的重要研究领域,利用1992.6、2002.6两期Landsat TM影像,采用监督分类和人机交互解译相结合的方法完成土地利用/覆盖类型的计算机解译,采用叠加分析方法,研究了山东半岛北部海岸带地区龙口市10年间土地利用的变化特征.结果表明:研究时段内园地、水浇地、水体、林地面积都有不同程度的减少;城乡用地、旱地、草地面积增加,其中城乡用地增幅最大,年变化率为5.34%;土地利用转换类型复杂多样,转换比例相对较大.相关性分析和主成分分析表明,该区土地利用变化主要受经济因素影响.     

基于土地转移流的干旱区河谷城市土地系统稳定性评价——以兰州市近郊四区为例

以位于西北的河谷型城市兰州市市区为例,引入流分析和土地利用活跃度分析,基于Landsat遥感影像数据,采用土地利用变化测度模型和主成分分析方法对研究区土地利用时空动态特征及其驱动机制进行了分析。研究表明:①研究区未利用土地资源较少,后备土地资源严重不足,林地、草地、水域比例较低,存在较大生态风险;②建设用地与耕地、草地、林地之间的转移关系是土地利用转移的关键关系,决定着研究区土地利用变化特征;③土地利用变化具有阶段性,随着社会经济高速发展,城镇化的快速推进导致土地系统熵值增加,稳定性降低。     

建三江垦区土地利用/覆盖变化与生态环境效应作用机理研究

以黑龙江省建三江垦区为研究区,以1989年和2006年两期TM遥感影像为主要信息源,利用遥感与地理信息系统相结合的方法,提取研究区土地利用/覆盖信息,运用数学模型计算土地利用/覆盖变化度并分析其总体特征,探讨选取用地类型变化的生态贡献率参数和生态环境指数,反映和揭示研究区土地利用/覆盖变化与生态环境响应。结果表明:土地利用/覆盖变化与生态环境相互作用和相互影响。1989-2006年,研究区土地利用/覆盖发生了很大的变化,水田和草地覆盖类型变化最为频繁、速度也最快,建设用地变化最慢。期间生态环境有恶化也有改善。在各种用地类型的变化中,沼泽湿地减少的生态贡献率最大,造成了生态环境的负面效应。研究表明,人们不合理的开发利用土地,会造成生态环境的恶化,从而使原有土地利用/覆盖方式被迫发生相应改变。     

巢湖流域土地利用/覆盖变化态势及生态系统服务价值时空变化研究

以巢湖流域为研究案例区,利用1991～2001年的土地利用详查和变更调查数据为主要数据源,分析了巢湖流域土地利用/覆盖变化的数量和流向特征以及引起的生态系统服务价值动态特征。结果显示:巢湖流域近10年来土地利用整体特征并未发生重大改变,以耕地和水域为主,耕地面积减少最多,建设用地占用是巢湖流域耕地减少的主要原因。流域利用与土地覆盖类型在流向转移过程中,主要集中在耕地与其他地类的相互转化上。巢湖流域生态系统服务价值以2002年为界,大体分为两个阶段,水域和林地生态系统服务价值在变化过程中起决定性作用。除了巢湖市以外,其他地市生态系统总服务价值与该地市面积之间成统一关系。肥东县和无为县的生态系统服务价值变化最大,巢湖市2001年之前变化不明显。     

北京市土地利用变化特征及驱动机制

以北京市为例,利用1985、2000和2010年三期土地利用数据,从土地利用变化幅度、土地利用变化速度、土地利用转移方向等方面,揭示了北京市1985—2010年的土地利用变化特征及相关驱动因子。结果表明:11985—2010年,北京市土地利用空间格局发生了较大变化,林地面积有一定程度的增加,耕地面积、水域面积减少较为迅速,建设用地扩张最为明显。21985—2000年,北京市土地利用综合动态度为0.99,土地利用变化速度较为平缓;2000—2010年,北京市土地利用综合动态度为1.64,土地利用类型变化速度呈加速趋势;从单一土地利用动态度来看,林地与建设用地的增加速度不断提升,由1985—2000年间的0.1383%、3.7808%增长到2000—2010年间的0.2078%、4.0088%;耕地、草地、水域面积不断减少,其中水域面积的减少速度最快。3从转移矩阵来看,1985—2000年,74.54%的耕地转化为建设用地,13.30%、11.24%的耕地转化为林地与水域;2000—2010年,耕地依然是各类用地增量的重要来源,建设用地向其他类型用地的转化面积是前一阶段的13.8倍。4从人口增长、经济发展、政府政策等方面研究了土地利用变化的驱动机制。     

基于三维景观格局指数的张家界市土地利用格局时空演化

在RS和GIS技术的支持下,基于三维景观方法选取面积/密度、边缘/形状、多样性3个方面的景观格局指数对典型山区张家界市1995—2015年的土地覆盖及其景观格局时空演化特征进行了分析。结果表明:20年来,研究区土地利用景观要素类型发生了明显变化,表现为耕地、草地面积大幅度减少,林地和建设用地面积大幅度增加,水域面积先增加后减少;耕地的主要去向是建设用地、林地和水域,林地增加的来源主要是草地和耕地。研究区景观格局20年来的总体变化情况是多样性指数先下降后升高,破碎度先减少后增加,景观异质性先降低后升高。同时,本研究显示,利用传统二维景观指数在进行定量描述该区景观格局变化时,低估了景观要素平均斑块面积,而三维景观格局指数由于引入了地形特征,对研究区景观格局及其动态变化反映则相对精确。     

Forecasting the price of gold

This article seeks to evaluate the appropriateness of a variety of existing forecasting techniques (17 methods) at providing accurate and statistically significant forecasts for gold price. We report the results from the nine most competitive techniques. Special consideration is given to the ability of these techniques to provide forecasts which outperforms the random walk (RW) as we noticed that certain multivariate models (which included prices of silver, platinum, palladium and rhodium, besides gold) were also unable to outperform the RW in this case. Interestingly, the results show that none of the forecasting techniques are able to outperform the RW at horizons of 1 and 9 steps ahead, and on average, the exponential smoothing model is seen providing the best forecasts in terms of the lowest root mean squared error over the 24-month forecasting horizons. Moreover, we find that the univariate models used in this article are able to outperform the Bayesian autoregression and Bayesian vector autoregressive models, with exponential smoothing reporting statistically significant results in comparison with the former models, and classical autoregressive and the vector autoregressive models in most cases.     

Planned adaptation in risk regulation: An initial survey of US environmental, health, and safety regulation

In principle, we want regulatory programs to be based on current realities, as reflected for example in the best knowledge of relevant experts. That would imply that old rules now on the books should be consistent with today's knowledge base, not just what was known when a rule or standard was originally set. This paper reports on a survey of US programs, examining how often existing rules are actually updated in light of better knowledge, and identifies five programs that attempt to make policy routinely adaptive. These programs exhibit what we term Planned Adaptation: they both revise rules when relevant new knowledge appears, and take steps to produce such improved knowledge. While Planned Adaptation is rare, it is used in several nationally prominent programs, including air pollution, airplane safety, and drug safety. Planned Adaptation is a policy tool that deserves more attention.     

The greenhouse effect: Damages,costs and abatement

The buildup of so-called greenhouse gases in the atmosphere — CO₂ in particular-appears to be having an adverse impact on the global climate. This paper briefly reviews current expectations with regard to physical and biological effects, their potential costs to society, and likely costs of abatement. For a worst case scenario it is impossible to assess, in economic terms, the full range of possible non-linear synergistic effects. In the most favorable (although not necessarily likely) case (of slow-paced climate change), however, it seems likely that the impacts are within the affordable range, at least in the industrialized countries of the world. In the third world the notion of affordability is of doubtful relevance, making the problem of quantitative evaluation almost impossible. We tentatively assess the lower limit of quantifiable climate-induced damages at $30 to $35 per ton of CO₂ equivalent, worldwide, with the major damages being concentrated in regions most adversely affected by sea-level rise. The non-quantifiable environmental damages are also significant and should by no means be disregarded.The costs and benefits of (1) reducing CFC use and (2) reducing fossil fuel consumption, as a means of abatement, are considered in some detail. This strategy has remarkably high indirect benefits in terms of reduced air pollution damage and even direct cost savings to consumers. The indirect benefits of reduced air pollution and its associated health and environmental effects from fossil-fuel combustion in the industrialized countries range from $20 to $60 per ton of CO₂ eliminated. In addition, there is good evidence that modest (e.g. 25%) reductions in CO₂ emissions may be achievable by the U.S. (and, by implication, for other countries) by a combination of increased energy efficiency and restructuring that would permit simultaneous direct economic benefits (savings) to energy consumers of the order of $50 per ton of CO₂ saved. A higher level of overall emissions reduction — possibly approaching 50% — could probably be achieved, at little or not net cost, by taking advantage of these savings.We suggest the use of taxes on fossil fuel extraction (or a carbon tax) as a reasonable way of inducing the structural changes that would be required to achieve significant reduction in energy use and CO₂ emissions. To minimize the economic burden (and create a political constituency in support of the approach) we suggest the substitution of resource-based taxes in general for other types of taxes (on labor, income, real estate, or trade) that are now the main sources of government revenue. While it is conceded that it would be difficult to calculate the optimal tax on extractive resources, we do not think this is a necessary prerequisite to policy-making. In fact, we note that the existing tax system has never been optimized according to theoretical principles, and is far from optimal by any reasonable criteria.During the academic year 1989–90 Dr. Ayres was at the International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.During the summer of 1989 Mr. Walter was a member of the Young Scientists' Summer Program at IIASA.     

SCIENCE AND INDUSTRY: TRACING THE FLOW OF BASIC RESEARCH THROUGH MANUFACTURING AND TRADE

This paper describes flows of basic research through the US economy during the late 20th century. In addition, the paper studies the effect of the flows on scientific papers in industries and fields. This article differs from others in its use of measures of science rather than technology. Together, its results present a picture of the structure of basic research flows in a modern, science-intensive economy. Basic research flows are large within petrochemicals and drugs, and within software and communications. Flows of chemistry, physics, and engineering are common throughout all industries – biology and medicine are almost confined to petrochemicals and drugs; and computer science is nearly as restricted to software and communications. In general, basic research flows are more concentrated within scientific fields than within industries. Our findings concerning the production of scientific papers indicate that the effect of a 1% change in academic R&D spillovers significantly exceeds that of industrial spillovers. In addition, within-field effects exceed effects between-fields, while within- and between-industry effects are roughly equal. It follows that scientific fields limit basic research flows more than industries do, perhaps because large firms implicitly span a range of industries.     

Valuing Mangrove-Fishery Linkages – A Case Study of Campeche, Mexico

This paper explores the value of mangrove systems as a breeding and nursery habitat for off-shore fisheries, focusing on mangrove-shrimp production linkages in Campeche State, Mexico. We develop an open access fishery model to account explicitly for the effect of mangrove area on carrying capacity and thus production. From the long-run equilibrium conditions of the model we are able to establish the key parameters determining the comparative static effects of a change in mangrove area on this equilibrium. We then estimate empirically the effects of changes in mangrove area in the Laguna de Terminos on the production and value of shrimp harvests in Campeche over 1980–90. Our findings suggest that mangroves are an important and essential input into the Campeche shrimp fishery, but that the low levels of deforestation between 1980 and 1990 mean that the resulting losses to the shrimp fishery are still comparatively small. Over-exploitation of the fishery due to open access conditions remains the more pervasive threat, and without better management any long-run benefits of protecting mangrove habitat are likely to be dissipated.     

Zvi Griliches's contributions to the economics of technology and growth*

Zvi Griliches's contributions to the economics of technology and growth are identified. Included is a discussion of his contributions on: the determinants of differences in speed of adoption of innovations; the use of patents to measure technology; the private and social returns to R&D; and spillover effects from R&D. Griliches's own evaluation of his research contribution is compared to the evaluation of others in the field, using as evidence citation counts of his works collected from the online Web of Science. Griliches's most important contribution is his 1957 Econometrica hybrid corn paper that is a foundation of the economics of technological innovation. Remarkably, the trend in annual citations to the paper has continued to increase for over 40 years. Finally, we summarize Griliches's most recent views on the practice of economics and on the most important unanswered questions in the economics of technology and growth.     

Evidence on the impact of R&D and ICT investments on innovation and productivity in Italian firms

Both research and development (R&D) and information and communication technology (ICT) investment have been identified as sources of relative innovation underperformance in Europe vis-à-vis the USA. In this article, we investigate the R&D and ICT investment at the firm level in an effort to assess their relative importance and to what extent they are complements or substitutes. We use data on a large unbalanced panel data sample of Italian manufacturing firms constructed from four consecutive waves of a survey of manufacturing firms, to estimate a version of the CDM model of R&D, innovation, and productivity [Crépon–Duguet–Mairesse 1998. Research, innovation and productivity: An econometric analysis at the firm level. Economics of Innovation and New Technology 7, no. 2: 115–58] that has been modified to include ICT investment and R&D as the two main inputs into innovation and productivity. We find that R&D and ICT are both strongly associated with innovation and productivity, with R&D being more important for innovation, and ICT investment being more important for productivity. For the median firm, rates of return to both investments are so high that they suggest considerably underinvestment in both these activities. We explore the possible complementarity between R&D and ICT in innovation and production, but find none, although we do find complementarity between R&D and worker skill in innovation.     

新员工主动社会化行为与组织承诺关系研究——以社会资本为中介变量

为了探索新员工主动社会化行为影响组织承诺的过程,本文对来自企业的401个有效样本进行了实证分析。本研究运用层级回归的方法,控制了人口统计变量的影响后,发现员工的搜寻信息和搜寻绩效反馈行为对组织承诺有直接的正面影响,同时,通过员工社会资本对员工组织承诺产生了间接的正面影响。社会资本在员工搜寻信息和搜寻绩效反馈行为影响组织承诺的机制中起部分中介作用。员工的关系构建行为对组织承诺没有显著影响,但对员工社会资本存在显著的正面影响。     

An Economic Analysis and Simulation of Woodfuel Management in the Sahel

This paper presents an economic framework and a computationalmethodology for assessing the evolution of woodfuel supply costsand the spatial distribution of biomass in a Sahelian woodlandsetting. Spatial data on standing stock and the costs oftransport to market are used to construct a supply curve for fuelto a fuel-consuming location. Given an exogenously specifieddemand, the model simulates, period by period, the extraction,regeneration, and transport of wood fuels. The model is appliedto evaluate the benefits and ecological impacts of scenarios forwoodland management around the city of N'Djamena, Chad.