Spatial dynamics of Norwegian tetraonid populations

Different species in a given site or population of a given species in different sites may fluctuate in synchrony if they are affected similarly by factors such as spatially autocorrelated climate, predation, or by dispersal between populations of one species. We used county wise time series of hunting bag records of four Norwegian tetraonid species covering 24 years to examine patterns of interspecific and intraspecific synchrony. We estimated synchrony at three spatial scales; national, regional (consisting of counties with similar climate), and county level. Ecologically related species with overlapping distributions exhibited strong synchrony across Norway, but there was much variation between the different regions and counties. Regions with a long coastline to both the North Sea and the Norwegian Ocean exhibited an overall stronger synchrony than those consisting of more continental areas. Intraspecific synchrony was generally low across all counties, but stronger synchrony between counties within regions defined by climatic conditions. Synchrony was negatively related to distance between populations in three of four species. Only the synchrony in willow ptarmigan showed a clear negative relationship with distance, while the other species had both strong positive and negative correlations at short distances. Strong interspecific synchrony between some species pairs within regions and weak intraspecific synchrony across counties within regions suggest a stronger synchronizing effect from environmental factors such as weather or predation and less effect from dispersal. Our results suggest that the complete tetraonid community is structured by environmental factors affecting the different species similarly and causes widespread interspecific synchrony. Local factors affecting the population dynamics nevertheless frequently forces neighbouring populations out of phase.     

极端干旱区绿洲生态用地规划

从保障极端干旱区生态安全、生物多样性以及土地资源的合理配置的目的出发,采用最小累积阻力模型,分析于田县生态源地空间扩张的最小阻力分布,在此基础上对生态用地保护的重要性进行分级,进而设置生态用地规划情景,同时对影响于田县生态用地空间分布的驱动因素进行了探讨。结果表明:(1)于田县生态用地分为生态核心区、生态控制区、生态过渡区、生态保护区4种类型,其面积分别为9622.20、1078.45、10846.70、8322.65 km~2,其中生态核心区和生态控制区主要分布在研究区南部昆仑山谷地和克里雅河及相关支流水域等沿岸;生态过渡区和生态保护区主要分布在东部和北部广大的荒漠戈壁区域。(2)于田县生态用地规划受到自然和社会经济因素多方面的制约,具体表现在受绿洲经济的发展、环境绿化建设、城镇化以及人口和收入等主要因子的影响。于田县生态用地规划以期为极端干旱区绿洲生态用地合理开发和保护提供了重要科学依据。     

Trends and scenarios of the carbon budget in postagricultural Puerto Rico (1936–2060)

Contrary to the general trend in the tropics, Puerto Rico underwent a process of agriculture abandonment during the second half of the 20th century as a consequence of socioeconomic changes toward urbanization and industrialization. Using data on land‐use change, biomass accumulation in secondary forests, and ratios between gross domestic product (GDP) and carbon emissions, we developed a model of the carbon budget for Puerto Rico between 1936 and 2060. As a consequence of land abandonment, forests have expanded rapidly since 1950, achieving the highest sequestration rates between 1980 and 1990. Regardless of future scenarios of demography and land use, sequestration rates will decrease in the future because biomass accumulation decreases with forest age and there is little agricultural land remaining to be abandoned. Due to high per‐capita consumption and population density, carbon emissions of Puerto Rico have increased dramatically and exceeded carbon sequestration during the second half of the 20th century. Although Puerto Rico had the highest percent of reforestation for a tropical country, emissions during the period 1950–2000 were approximately 3.5 times higher than sequestration, and current annual emission is almost nine times the rate of sequestration. Additionally, while sequestration will decrease over the next six decades, current socioeconomic trends suggest increasing emissions unless there are significant changes in energy technology or consumption patterns. In conclusion, socioeconomic changes leading to urbanization and industrialization in tropical countries may promote high rates of carbon sequestration during the decades following land abandonment. Initial high rates of carbon sequestration can balance emissions of developing countries with low emission/GDP ratio. In Puerto Rico, the socioeconomic changes that promoted reforestation also promoted high‐energy consumption, and resulted in a net increase in carbon emissions.     

Is Yield Increase Sufficient to Achieve Food Security in China?

Increasing demand for food, driven by unprecedented population growth and increasing consumption, will keep challenging food security in China. Although cereal yields have substantially improved during the last three decades, whether it will keep thriving to meet the increasing demand is not known yet. Thus, an integrated analysis on the trends of crop yield and cultivated area is essential to better understand current state of food security in China, especially on county scale. So far, yield stagnation has extensively dominated the main cereal-growing areas across China. Rice yield is facing the most severe stagnation that 53.9% counties tracked in the study have stagnated significantly, followed by maize (42.4%) and wheat (41.9%). As another important element for production sustainability, but often neglected is the planted area patterns. It has been further demonstrated that the loss in productive arable land for rice and wheat have dramatically increased the pressure on achieving food security. Not only a great deal of the planted areas have stagnated since 1980, but also collapsed. 48.4% and 54.4% of rice- and wheat-growing counties have lost their cropland areas to varying degrees. Besides, 27.6% and 35.8% of them have retrograded below the level of the 1980s. The combined influence (both loss in yield and area) has determined the crop sustainable production in China to be pessimistic for rice and wheat, and consequently no surprise to find that more than half of counties rank a lower level of production sustainability. Therefore, given the potential yield increase in wheat and maize, as well as substantial area loss of rice and wheat, the possible targeted adaptation measures for both yield and cropping area is required at county scale. Moreover, policies on food trade, alongside advocation of low calorie diets, reducing food loss and waste can help to enhance food security.     

Drinking Water in Transition: A Multilevel Cross-sectional Analysis of Sachet Water Consumption in Accra

Rapid population growth in developing cities often outpaces improvements to drinking water supplies, and sub-Saharan Africa as a region has the highest percentage of urban population without piped water access, a figure that continues to grow. Accra, Ghana, implements a rationing system to distribute limited piped water resources within the city, and privately-vended sachet water–sealed single-use plastic sleeves–has filled an important gap in urban drinking water security. This study utilizes household survey data from 2,814 Ghanaian women to analyze the sociodemographic characteristics of those who resort to sachet water as their primary drinking water source. In multilevel analysis, sachet use is statistically significantly associated with lower overall self-reported health, younger age, and living in a lower-class enumeration area. Sachet use is marginally associated with more days of neighborhood water rationing, and significantly associated with the proportion of vegetated land cover. Cross-level interactions between rationing and proxies for poverty are not associated with sachet consumption after adjusting for individual-level sociodemographic, socioeconomic, health, and environmental factors. These findings are generally consistent with two other recent analyses of sachet water in Accra and may indicate a recent transition of sachet consumption from higher to lower socioeconomic classes. Overall, the allure of sachet water displays substantial heterogeneity in Accra and will be an important consideration in planning for future drinking water demand throughout West Africa.     

Open Space Loss and Land Inequality in United States' Cities, 1990–2000

Urban growth reduces open space in and around cities, impacting biodiversity and ecosystem services. Using land-cover and population data, we examined land consumption and open space loss between 1990 and 2000 for all 274 metropolitan areas in the contiguous United States. Nationally, 1.4 million ha of open space was lost, and the amount lost in a given city was correlated with population growth (r(272) = 0.85, P<0.001). In 2000, cities varied in per capita land consumption by an order of magnitude, from 459 m²/person in New York to 5393 m²/person in Grand Forks, ND. The per capita land consumption (m²/person) of most cities decreased on average over the decade from 1,564 to 1,454 m ²/person, but there was substantial regional variation and some cities even increased. Cities with greater conservation funding or more reform-minded zoning tended to decrease in per capita land consumption more than other cities. The majority of developed area in cities is in low-density neighborhoods housing a small proportion of urban residents, with Gini coefficients that quantify this developed land inequality averaging 0.63. Our results suggest conservation funding and reform-minded zoning decrease per capita open space loss.     

区县生态系统健康评价方法——以东莞市各镇区为例

现有城市生态系统健康研究多集中在城市及城市群层面,未能深入探究城市内部特征。鉴于此,聚焦区县生态系统健康状况,进一步探究城市内部的健康分布特征;提出了"发展水平-服务功能-抵御干扰-自我维育"四维区县生态系统健康评价框架,并建立了相应的多层级指标体系,构建了区县生态系统健康评价模型;在分析区县生态系统健康变化过程及空间分异特征的基础上,识别区县生态系统健康的主要贡献因子。针对东莞各镇区的研究结果表明：1995-2015年间,各镇区生态系统健康状态总体趋于恶化,其中西南地区生态系统的退化比东南地区更为明显。自我维育对各镇区生态系统健康变化具有重要影响,主要瓶颈在于快速发展过程中土地资源的稀缺及较低的利用效率。对区县生态系统健康的研究可以帮助决策者了解城市生态系统复杂的内部特征,在此基础上更好地平衡区域发展、维护城市生态系统健康。     

Influence of primary care physician availability and socioeconomic deprivation on breast cancer from 1988 to 2008: a spatio-temporal analysis

Background

Breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer death among women in the United States. It is unclear how county-level primary care physician (PCP) availability and socioeconomic deprivation affect the spatial and temporal variation of breast cancer incidence and mortality.

Methods

We used the 1988–2008 public-use county-based data from nine Surveillance, Epidemiology, and End Results (SEER) programs to analyze the temporal and spatial disparity of PCP availability and socioeconomic deprivation on early-stage incidence, advanced-stage incidence and breast cancer mortality. The spatio-temporal analysis was implemented by a novel structural additive modeling approach.

Results

Greater PCP availability was significantly associated with higher early-stage incidence, advanced-stage incidence and mortality during the entire study period while socioeconomic deprivation was significantly negatively associated with early-stage incidence, advanced-stage incidence, and mortality up to 1992. However, the observed influence of PCP availability and socioeconomic deprivation varied by county.

Conclusions

We showed important associations of PCP availability and socioeconomic deprivation with the three breast cancer indicators. However, the effect of these associations varied over time and across counties. The association of PCP availability and socioeconomic deprivation was stronger in selected counties.     

Where Are Socioeconomically Deprived Immigrants Located in Chile? A Spatial Analysis of Census Data Using an Index of Multiple Deprivation from the Last Three Decades (1992-2012)

Introduction and Purpose of the Study

Immigrants in Chile have diverse characteristics and include socioeconomically deprived populations. The location of socioeconomically deprived immigrants is important for the development of public policy intelligence at the local and national levels but their areas of residence have not been mapped in Chile. This study explored the spatial distribution of socioeconomic deprivation among immigrants in Chile, 1992–2012, and compared it to the total population.

Material and Methods

Areas with socioeconomically deprived populations were identified with a deprivation index which we developed modelled upon the Index of Multiple Deprivation (IMD) for England. Our IMD was based upon the indicators of unemployment, low educational level (primary) and disability from Census data at county level for the three decades 1992, 2002 and 2012, for 332, 339 and 343 counties respectively. We developed two versions of the IMD one based on disadvantage among the total population and another focused upon the circumstances of immigrants only. We generated a spatial representation of the IMD using GIS, for the overall IMD score and for each dimension of the index, separately. We also compared the immigrants´ IMD to the total population´s IMD using Pearson´s correlation test.

Results

Results showed that socioeconomically deprived immigrants tended to be concentrated in counties in the northern and central area of Chile, in particular within the Metropolitan Region of Santiago. These were the same counties where there was the greatest concentration of socioeconomic deprivation for the total population during the same time periods. Since 1992 there have been significant change in the location of the socioeconomically deprived populations within the Metropolitan Region of Santiago with the highest IMD scores for both the total population and immigrants becoming increasingly concentrated in the central and eastern counties of the Region.

Conclusion

This is the first study analysing the spatial distribution of socioeconomic deprivation among international immigrants and the total population in a Latin American country. Findings could inform policy makers about location of areas of higher need of social protection in Chile, for both immigrants and the total resident population in the country.     

Area-Based Socioeconomic Position and Adult Glioma: A Hierarchical Analysis of Surveillance Epidemiology and End Results Data

Background

Glioma rates vary by demographic factors and geo-political boundaries and this variation suggests higher glioma rates in groups of higher socioeconomic position. The primary goal of this analysis is to investigate the relationship between glioma and county socioeconomic position using U.S. Surveillance Epidemiology and End Results (SEER) data.

Methods

Cases were individuals 25+ years diagnosed with glioma between 2000 and 2006 and residing within the SEER-17 catchment area. County-, sex-, race-, age-specific rates were created in order to investigate individual-level associations (population data from U.S. Census 2000). A Bayesian hierarchical Poisson spatial conditionally autoregressive (CAR) model was utilized to simultaneously estimate individual- and county-level associations while controlling for county spatial dependence.

Results

Those residing in counties of the second, third, and fourth highest quartiles of socioeconomic position have glioma incidence rates that are 1.10 (95% CI: 1.02,1.19), 1.11 (95% CI: 1.02,1.20), 1.14 (95% CI: 1.05,1.23) times that of the first quartile, respectively. A CAR model properly controlled for error spatial dependence. Investigated lag times suggest year 2000 census data yields superior model fit.

Conclusion

Demographically adjusted rates of glioma are elevated in counties of higher socioeconomic position. More well-grounded theory concerning the glioma-socioeconomic position association along with socioeconomic data collected at multiple levels is recommended for future studies investigating this relationship.     

城市扩张过程中建设用地景观格局演变特征及其驱动力

剖析城市扩张过程中建设用地景观格局演变特征及其驱动力,不仅有助于城市生态环境问题的解决,而且为城市用地结构优化、城市景观规划等工作提供科学依据。以快速城市化的中型城市—扬州市为例,利用多期(1995、2000、2005、2010年和2015年)Landsat卫星影像、乡镇水平的扬州统计年鉴等数据,运用景观格局分析、增强回归树(Boosted regression trees)等方法,研究建设用地的扩张模式、形态及景观格局,定量探究地理、社会和经济因子对景观格局的影响机制,从而明晰景观格局演变特征及其驱动力。结果表明,1995—2015年,建设用地面积持续增加,填充式(Infilling)、边缘式(Edge-expansion)和跳跃式(Leapfrog)3种扩张模式在各时段均有出现,但其优势度随着城市发展而改变。建设用地的形态在城市扩张的过程中经历着"集聚"和"扩散"的交替变化过程,景观格局则出现了同质化倾向,景观破碎化下降、聚合度增加。地理因子(海拔和到县市中心的距离)对景观格局的综合影响虽然高于社会经济,但它的影响力却随着城市发展呈现出下降趋势,社会经济的作用则逐渐增强。海拔和人口密度的增加会促进景观的破碎化、抑制景观的集聚;人口数量的增加会促进景观的集聚、降低景观的破碎化;其余因子(到县市中心的距离、人均GDP和第二产业占比)的作用则随城市的发展而发生转变,如人均GDP对景观破碎化的作用表现为"促进→抑制"的转变、第二产业则为"抑制→促进"。     

基于保护生态服务价值的县域城市扩展情景分析——以浙江省安吉县为例

县域城市的可持续发展是推动生态文明建设、实现特色新型城镇化战略目标的重要基础,以保护生态服务价值为目标的县域城市扩展研究具有重要理论和现实意义。运用SLEUTH模型,以两山理论发源地安吉县为例,并与毗邻的广德市进行对比,预置了两县市现有发展模式和生态保护模式两种不同的发展情景,并基于生态服务价值进一步将生态保护情景分为保护调节服务、供给服务、支持服务和娱乐服务4种情景。对不同情景下的2030年建设用地扩展进行模拟和对比分析,以探究生态保护情景下的建设用地扩展对县域经济的影响。结果显示：（1）现有发展模式下,两县市仍围绕当前建设用地向周围蔓延,在明显的外延式增长下还伴随着内部填充,集中扩张区均围绕县城及各镇政府所在地并呈现集中连片趋势,这种模式势必对生态环境产生负面影响;（2）生态保护情景下,两县市均在一定程度上抑制了建设用地的扩张,安吉县扩张面积最低减少1.43%,广德市扩张面积最低减少7.57%。（3）相比于现有发展模式,两县市对林地的占用量显著降低,安吉县对林地的占用减少了1.79km²,广德市减少了2.44km²;（4）安吉县相较广德市的建设用地扩展更多依赖耕地转换,因安吉县最先走生态保护道路,故生态保护情景对建设用地扩展的影响已明显小于广德市。     

Environmental and human demographic features associated with epizootic raccoon rabies in Maryland, Pennsylvania, and Virginia

We assessed land use and demographic data as predictors discriminating between counties experiencing large or small first epizootics of rabies among raccoons (Procyon lotor). Monthly county reports of raccoons testing positive for rabies were obtained from rabies surveillance databases from Maryland, Pennsylvania, and Virginia (USA). Environmental and demographic data for the three states were obtained from public sources. On the basis of total reports of raccoon rabies during the first defined epizootic period, the 203 counties were dichotomized at the 75th percentile as having a large epizootic (> or = 24 rabid raccoons in the first epizootic) (51 counties) or a small epizootic or no epizootic (152 counties). A high percentage of agricultural land use [OR = 9.1, 95% CI (3.6-23.1)], high water coverage in combination with low human population density [OR = 8.8, 95% CI (2.9-27.0)], and low water coverage with high human population density [OR = 11.7, 95% CI (4.0-34.1)] were positively associated with large rabies epizootics. Counties with more than 15% of mixed forest were less likely to experience large epizootics than were counties with < or = 15% of mixed forest [OR = 0.3, 95% CI (0.1, 0.9)]. A combination of land use and human population density measures provided the best model for determining epizootic size and may be important predictors of epizootic behavior and risk of exposure to this reservoir species.     

Climate amenity and BMI

Objectives: Our goal was to examine the relationship between BMI and climate amenable for physical activity at the county level in the U.S. Research Methods and Procedures: Using Geographic Information Systems tools and 6‐year National Oceanic and Atmospheric Administration station hourly weather records, an index of amenable climate was derived for all U.S. counties. This index was linked to individual BMI in a multi‐level analysis that accounted for other individual characteristics from the 2002 survey of the Behavioral Risk Factor Surveillance System. Results: There was an inverse relationship between climate amenable to physical activity and BMI at the county level after controlling for individual risk factors, county road density, and median household income and unemployment rate. Residents in high climate‐amenity counties tended to have a lower BMI. Discussion: The contribution of less amenable climate to overweight and obesity in the U.S. is likely to be substantial because it cuts across wide geographic areas. Health promotion strategies that promote mixed land use or other urban design conducive to walking and other physical activities should consider broader environmental disamenities to mitigate their influence. Strategies for outdoor physical activity should also be tailored for people of different racial groups and educational backgrounds due to observed differences in their response to climate amenity.     

生态足迹的模型修正与方法改进

生态足迹是测定人类活动的资源消费需求,判明自然资产是否被过度利用的有效工具。介绍了生态足迹的基本概念和模型,简单分析基本模型存在的主要缺陷和争论,重点解析了近年来生态足迹模型在参数调整、项目计算、账户扩展等方面的演变和修正。介绍生态足迹研究的传统方法:综合法和组分法,评述了生命周期评价,基于投入产出分析,三维模型,净初级生产力,能值理论,时序分析等的方法改进。对未来的研究方向提出自己的看法,期望对我国的生态足迹研究有一定的启示作用。     

Disparities in distribution of COVID-19 vaccines across US counties: A geographic information system–based cross-sectional study

BackgroundThe US Centers for Disease Control and Prevention has repeatedly called for Coronavirus Disease 2019 (COVID-19) vaccine equity. The objective our study was to measure equity in the early distribution of COVID-19 vaccines to healthcare facilities across the US. Specifically, we tested whether the likelihood of a healthcare facility administering COVID-19 vaccines in May 2021 differed by county-level racial composition and degree of urbanicity.Methods and findingsThe outcome was whether an eligible vaccination facility actually administered COVID-19 vaccines as of May 2021, and was defined by spatially matching locations of eligible and actual COVID-19 vaccine administration locations. The outcome was regressed against county-level measures for racial/ethnic composition, urbanicity, income, social vulnerability index, COVID-19 mortality, 2020 election results, and availability of nontraditional vaccination locations using generalized estimating equations.Across the US, 61.4% of eligible healthcare facilities and 76.0% of eligible pharmacies provided COVID-19 vaccinations as of May 2021. Facilities in counties with >42.2% non-Hispanic Black population (i.e., > 95th county percentile of Black race composition) were less likely to serve as COVID-19 vaccine administration locations compared to facilities in counties with <12.5% non-Hispanic Black population (i.e., lower than US average), with OR 0.83; 95% CI, 0.70 to 0.98, p = 0.030. Location of a facility in a rural county (OR 0.82; 95% CI, 0.75 to 0.90, p < 0.001, versus metropolitan county) or in a county in the top quintile of COVID-19 mortality (OR 0.83; 95% CI, 0.75 to 0.93, p = 0.001, versus bottom 4 quintiles) was associated with decreased odds of serving as a COVID-19 vaccine administration location.There was a significant interaction of urbanicity and racial/ethnic composition: In metropolitan counties, facilities in counties with >42.2% non-Hispanic Black population (i.e., >95th county percentile of Black race composition) had 32% (95% CI 14% to 47%, p = 0.001) lower odds of serving as COVID administration facility compared to facilities in counties with below US average Black population. This association between Black composition and odds of a facility serving as vaccine administration facility was not observed in rural or suburban counties. In rural counties, facilities in counties with above US average Hispanic population had 26% (95% CI 11% to 38%, p = 0.002) lower odds of serving as vaccine administration facility compared to facilities in counties with below US average Hispanic population. This association between Hispanic ethnicity and odds of a facility serving as vaccine administration facility was not observed in metropolitan or suburban counties.Our analyses did not include nontraditional vaccination sites and are based on data as of May 2021, thus they represent the early distribution of COVID-19 vaccines. Our results based on this cross-sectional analysis may not be generalizable to later phases of the COVID-19 vaccine distribution process.ConclusionsHealthcare facilities in counties with higher Black composition, in rural areas, and in hardest-hit communities were less likely to serve as COVID-19 vaccine administration locations in May 2021. The lower uptake of COVID-19 vaccinations among minority populations and rural areas has been attributed to vaccine hesitancy; however, decreased access to vaccination sites may be an additional overlooked barrier.

Inmaculada Hernandez and colleagues investigate the disparities in early-phase distribution of COVID-19 Vaccines across U.S. Counties.     

Environmental Predictors of US County Mortality Patterns on a National Basis

A growing body of evidence has found that mortality rates are positively correlated with social inequalities, air pollution, elevated ambient temperature, availability of medical care and other factors. This study develops a model to predict the mortality rates for different diseases by county across the US. The model is applied to predict changes in mortality caused by changing environmental factors. A total of 3,110 counties in the US, excluding Alaska and Hawaii, were studied. A subset of 519 counties from the 3,110 counties was chosen by using systematic random sampling and these samples were used to validate the model. Step-wise and linear regression analyses were used to estimate the ability of environmental pollutants, socio-economic factors and other factors to explain variations in county-specific mortality rates for cardiovascular diseases, cancers, chronic obstructive pulmonary disease (COPD), all causes combined and lifespan across five population density groups. The estimated models fit adequately for all mortality outcomes for all population density groups and, adequately predicted risks for the 519 validation counties. This study suggests that, at local county levels, average ozone (0.07 ppm) is the most important environmental predictor of mortality. The analysis also illustrates the complex inter-relationships of multiple factors that influence mortality and lifespan, and suggests the need for a better understanding of the pathways through which these factors, mortality, and lifespan are related at the community level.     

Global distribution patterns of highly pathogenic H5N1 avian influenza: Environmental vs. socioeconomic factors

In this report, we quantitatively analyzed the essential ecological factors that were strongly correlated with the global outbreak of highly pathogenic H5N1 avian influenza. The ecological niche modeling (ENM) was used to reveal the potential outbreak hotspots of H5N1. A two-step modeling procedure has been proposed: we first used BioClim model to obtain the coarse suitable areas of H5N1, and then those suitable areas with very high probabilities were retained as the inputs of multiple-variable autologistic regression analysis (MAR) for model refinement. MAR was implemented taking spatial autocorrelation into account. The final performance of ENM was evaluated using the areas under the curve (AUC) of receiver-operating characteristic. In addition, principal component analysis (PCA) was employed to reveal the most important variables and relevant ecological gradients of H5N1 outbreak. Niche visualization was used to identify potential spreading trend of H5N1 along important ecological gradients. For the first time, we combined socioeconomic and environmental variables as joint predictors in developing ecological niche modeling. Environmental variables represented the natural element related to H5N1 outbreak, whereas socioeconomic ones represented the anthropogenic element. Our results indicated that: (1) the high-risk hotspots are mainly located in temperate zones (indicated by ENM)—correspondingly, we argued that the “ecoregions hypothesis” was reasonable to some extent; (2) evaporation, humidity, human population density, livestock population density were the first four important factors (in descending order) that were associated with the H5N1 global outbreak (indicated by PCA); (3) influenza had a tendency to expand into areas with low evaporation (indicated by niche visualization). In conclusion, our study substantiates that both the environmental and socioeconomic variables jointly determined the global spreading trend of H5N1, but environmental variables played a more important role. Consequently, our study is consistent with the assumption that the natural element is more important than the anthropogenic element as the underlying ecological mechanisms explaining global H5N1 transmission.     

基于耕地能值-生态足迹的耕地休耕规模研究——以贵州省松桃县为例

区域耕地休耕规模测算是耕地休耕空间配置的重要组成部分,从资源承载力视角理解,其本质是将休耕空间布局于耕地资源承载力相对较低的区域。立足于从区域耕地生态经济系统探索耕地休耕规模,运用能值分析方法和生态足迹方法,以生态严重退化地区、国家第一批休耕试点县的贵州省松桃县为案例区,修正了耕地能值生态足迹改进模型（EC和EF,简称"修正模型"）与耕地能值可持续指数（ESI_cl）,测算了松桃县2016年休耕面积范围值。结果表明：（1）耕地能值生态盈亏可以作为乡镇是否应该休耕的判定标准,基于此测算的最大休耕面积关键在于测算生态耕地面积。总体来看,全县耕地能值生态赤字,应该安排耕地休耕;从分乡镇来看,有3个乡镇可以不休耕、25个乡镇应该休耕。按照全县平均统计（SCAL）和按照分乡镇统计（STL）,全县最大休耕面积分别19558.62hm²和17673.83hm²。最大休耕面积中等及以上等级的乡镇散布于4个区域的8个乡镇。（2）ESI_cl可以作为休耕乡镇时序的判定标准,其优先休耕乡镇的最大休耕面积之和即为全县最小休耕面积。全县ESI_cl偏低,应该适度休耕。优先休耕、适度休耕和暂不休耕的乡镇分别有2个、23个和3个。全县最小休耕面积1396.10hm²,占耕地面积的1.88%。按照全县平均统计（SCAL）,全县休耕面积范围值1396.10-19558.62hm²,占总耕地面积的1.88%-26.34%;按照分乡镇统计（STL）,全县休耕面积1396.10-17673.83hm²,占总耕地面积的1.88%-23.8%。修正模型和ESI_cl为测算区域休耕规模提供了更加科学的技术方法,以期为其他类似区域开展休耕实践提供借鉴。