Dynamics of photosynthetic pigments in an Andean lake in Colombia

Guatavita Lake is a small, sheltered tropical high mountain lake located in the Colombian Andes, with a closed watershed and a maximum depth of 25 m. It is the freshwater source for human consumption in nearby small towns, as well as being a site of cultural value for the country, as it was a sacred place to indigenous peoples until about five centuries ago. As the structure and function of this aquatic ecosystem is poorly understood, this study provides initial knowledge on its phytoplankton biomass dynamics, which should be useful in designing efficient management plans with environmental baseline information for similar lakes elsewhere. Physical and chemical data, and photosynthetic pigment concentrations, were measured for the period November 1999–November 2000 at the central vertical axis of Guatavita Lake. The vertical profile of the chlorophyll‐a concentration was closely related to the dissolved inorganic nitrogen concentrations and the thermal stratification characteristics. The maximum chlorophyll‐a concentration in the metalimnion was recorded for the thermal stratification period (November 1999–June 2000). Deepening of the maximum chlorophyll‐a concentration began in February, continuing to June, when it reached its lowest value at the 15 m depth. The phytoplankton biomass values showed an increment within the entire water column at the beginning of the mixing period (July). The relation between the metalimnetic peak of chlorophyll‐a and the dissolved inorganic nitrogen concentration suggests the growth of the phytoplankton community is limited mainly by the availability of nitrogen.     

变化环境下河流健康评价研究进展

全球以温度升高为主要特征的气候变化耦合人类活动影响,造成了全球性变化环境背景下大范围的水资源危机、水环境污染和水生态退化问题,威胁河流健康,已成为当今世界各国急需解决的难题。针对变化环境背景,分别从河流健康的概念和内涵、河流健康评价的内容、方法及应用等方面,评述近年来国内外河流健康评价的研究进展。将河流健康定义为,特定时期一定的社会公众价值体系下,在保障河流自身基本生存需求的前提下,能够持续地为人类社会提供高效合理的生态服务功能,并实现服务功能综合价值最大化。在前人研究基础上,指出变化环境下河流健康评价研究存在的主要问题,如河流健康概念及内涵仍存在争议,河流健康变化的驱动机制尚不明确,河流健康评价的理论及方法有待完善,河流健康评价实践滞后及评价结果未能有效指导河流管理等。提出变化环境下河流健康评价的发展趋势:以流域为基本空间尺度结合多时间尺度开展河流健康评价与调控研究,因地制宜开展河流健康评价指标体系及评价标准研究,开展基于3S等技术的河流健康评价研究,建立长期且全面的河流健康监测网络,科学界定河流健康的"基准点",以及开展河流健康评价与水资源调控的集成研究等。     

云南热区种植草果的生态经济效益分析

本文介绍了云南热区种植草果的概况及经营技术，并对所产生的生态经济效益进行了分析。     

Sustainable resource use,economic development,and public regulation

The role of production technology for sustainable economic growth and resource management in the multispecies renewable resources industries is a neglected issue, particularly in complex tropical ecosystems. Given the still rudimentary understanding of biological interactions among species, even in most temperate ecosystems, the importance of under-standing the technological and economic interactions is heightened for sustainable economic growth and public regulation. This paper evaluates these interactions for the multiproduct gill net fisheries of Peninsular Malaysia. Standard price and quantity controls may have little promise. Gear regulations, a policy of constant escapement, and managing the entire mix of species as a single stock for economic rather than biomass yield appear the most promising management tools given the limited regulatory options.     

Reassessing the risk conditions for political instability in the light of the Arab Spring

In today’s globalized world, multinational firms contend with a diverse set of risk factors in their worldwide operations. The recent regime changes in northern African countries, also called the Arab Spring, have highlighted that political instability is one of these factors. As researchers and existing indices of political instability largely failed to predict those developments, firms had not incorporated them into their risk calculations and hence incurred losses while having to adapt their operations. This paper examines the conditions that contributed to the recent instability in North Africa using Tunisia and Egypt as case studies. It evaluates the extent to which existing measures of political instability incorporate those conditions. The analysis reveals that the main conditions contributing to the political turmoil can be seen in socio-economic factors, namely inequality, poverty, youth unemployment, a growing youth population, and especially in the case of Egypt an independent military. These findings reveal gaps in current measures of political instability, whose dominant focus is on factors describing violence and changes in the political system while neglecting the influence of a country’s socio-economic environment.     

Wholly owned foreign subsidiary relation-based strategies in volatile environments

Drawing from dynamic capability, institutional, nonmarket strategy, and social-network literatures, we detail wholly owned subsidiary (WOFSs) relation-based strategies (RBSs). We explain how deploying RBSs with key nonmarket and market actors will create competitive advantages for WOFSs operating in volatile emerging market environments. We posit that dynamic capabilities will drive the deployment of RBSs by WOFSs, and argue that the positive relationship between dynamic capabilities and RBS deployment will strengthen as perceived institutional uncertainty increases. We further suggest that the greater the strength and frequency of RBS deployment, the more likely that a WOFS will establish a combination of nonmarket-based and market-based embedded assets. Also, our theory proposes that greater integration of nonmarket-based and market-based assets will enhance WOFS financial performance outcomes. Implications for future research are discussed.     

The impact of relative residence times on the distribution of heavy drinkers in highly distinct environments

Alcohol consumption is a function of social dynamics, environmental contexts, individuals' preferences and family history. Empirical surveys have focused primarily on identification of risk factors for high-level drinking but have done little to clarify the underlying mechanisms at work. Also, there have been few attempts to apply nonlinear dynamics to the study of these mechanisms and processes at the population level. A simple framework where drinking is modeled as a socially contagious process in low- and high-risk connected environments is introduced. Individuals are classified as light, moderate (assumed mobile), and heavy drinkers. Moderate drinkers provide the link between both environments, that is, they are assumed to be the only individuals drinking in both settings. The focus here is on the effect of moderate drinkers, measured by the proportion of their time spent in “low-” versus “high-” risk drinking environments, on the distribution of drinkers.A simple model within our contact framework predicts that if the relative residence times of moderate drinkers are distributed randomly between low- and high-risk environments then the proportion of heavy drinkers is likely to be higher than expected. However, the full story even in a highly simplified setting is not so simple because “strong” local social mixing tends to increase high-risk drinking on its own. High levels of social interaction between light and moderate drinkers in low-risk environments can diminish the importance of the distribution of relative drinking times on the prevalence of heavy drinking.     

Cost-effective compensation to avoid carbon emissions from forest loss: An approach to consider price-quantity effects and risk-aversion

Analyses were carried out on financial compensation to avoid loss of tropical forests and related carbon (C) emissions when marginal financial yield declined for land-use options with extended areas, and when a risk-averting perspective (modeled according to financial theory around the capital asset pricing model) is assumed. The approach in this study was to consider natural forest, forest plantation, pasture, and cropland simultaneously to investigate how an optimized land-use distribution may reduce the amount of compensation necessary to avoid C emissions from forest loss.The financial compensations derived were as high as US$ 176 per hectare per year when comparing natural forests only with the most profitable alternative (croplands). However, compensation decreased to US$ 124 for risk-neutral decision-makers, who would strive for optimized land-use allocation, and to only US$ 47 per hectare per year for risk-avoiders, who would look to maximize the reward-to-variability ratio. Sensitivity analyses indicated that the compensation under risk-aversion increased much less than under risk-ignoring when increased productivity of agricultural land-use or growing demand for agricultural products was simulated. It was concluded that considering appropriate diversification strategies and the well documented human behavior to avoid risks is an important step in developing cost-effective compensation policies.     

制度环境、政治联系与民营企业债务期限结构

以2007-2009年在沪深上市的民营上市公司为研究样本,对制度环境、政治联系如何影响企业债务期限结构进行分析。研究发现:在法律环境较差、地区金融发展水平落后、政府干预较强的地区,民营企业长期债务的比重越大。在考虑企业家政治背景后发现,政治联系有助于民营企业获得更多的长期债务,特别是在制度环境较差地区,政治联系的这种效应更显著。这表明,政治联系是制度环境不完善条件下的一种替代机制。     

海南热带观光农业发展现状与建议

介绍海南省热带观光农业发展的现状,将之同台湾热带观光农业进行了对比分析,建议要充分利用农业科技优势,合理规划热带农业资源,挖掘热带农业文化内涵,加强对海南热带农业资源的保护;以及琼台合作,进一步发展海南热带观光农业产业。