基于随机森林的耕地利用效率测度模型构建及其应用

构建合适的量化分析模型是科学把握耕地利用状况及利用效率的基础性工作,可为制定合理有效的耕地资源管控政策,实现耕地利用与生态环境的协调发展提供决策依据。为了更准确地反映耕地利用系统的复杂性、动态性及差异性等特征,鉴于随机森林的基本思想,运用随机抽样Bootstrap法在合理构建分类树的基础上,构造了耕地利用效率测度的RF模型,进而以中国粮食主产区172个城市为例训练该模型并将其运用至2003-2015年的耕地利用效率测度中,同时将BP神经网络和熵权法作为对比验证其一致性、代表性和优越性。结果表明：（1）耕地利用效率测度的RF模型不受量纲限制,运行所需参数少,运算过程简化,能够较为精确地模拟各评价指标间的复杂联系,科学量化各评价指标对耕地利用效率的贡献。（2）对同一空间单元的效率值而言,RF>BPNN>EW,RF与BPNN所得效率值的总体分布格局相似,且均与EW的测度结果存在较大差异。（3）从评价结果与现实的匹配度和精度表征参数来看,RF的测度结果与自然和社会经济发展等客观事实更相符,具有较高的适用性与可靠性。同时,与其余两种常用模型相比,RF能够降低计算复杂度,提高训练效率,其测度结果的相关系数R为0.8685,M_RPD为2.3533,且具有最小M_MSE0.0174和M_MAE0.0211,更适用于复杂非线性特征的耕地利用效率研究。     

京津冀及周边地区大气污染综合立体观测网的建设与应用

京津冀及周边地区大气染污综合立体观测网针对的是大气重污染发生-演变-消散全过程的核心科学问题,通过制定适用于京津冀及周边地区的大气污染综合观测技术规范,建立了区域大气污染综合立体观测网,开展了近地面及大气边界层气象和大气化学过程的同步观测,构建了监测数据综合分析及共享应用平台,实现了大气环境多源数据综合管理业务化,为大气重污染成因研究提供精准数据集,提升了京津冀秋冬季重污染成因机制研究和精细化源解析的能力,推动了京津冀及周边地区空气质量的持续改善.京津冀及周边地区大气污染综合立体观测网开展了传输通道的加密观测,增加了背景站和手工采样点观测,建立了包括黑碳、氨和重金属等多要素的关键站点,并充分利用了服务于科学研究的超级站和垂直梯度观测技术.京津冀及周边地区大气污染综合立体观测网和数据平台的建立,实现了业务部门与科研部门数据的有效融合与综合管理业务化,具有效率高、代表性好、目的性强的特点,能够很好地应对决策部门不断提高的管理需求.观测网络和平台充分吸取了国外的先进技术和观测经验,保证了观测网长期稳定运行;通过综合环境空气质量监测预警和发布平台,为环境空气质量监测和污染成因综合研究提供技术支撑,最终为实现我国空气质量的全面改善奠定了坚实的基础.      

Overall Planning of Development of Urban-Rural Areas:A Policy Mechanism for Urban-Rural Coordinated Growth

While analyzing overall planning and coordinated development of urban-rural areas, this paper shows that overall planning for the development of urban-rural areas is a requirement for the best use of productive forces. It means the setting up of a policy mechanism for coordinated growth. Recognizing this, the government should set up a way to lead and manage a unified program to increase service and decrease controlling administration power, while safeguarding and fulfilling the farmers' ownership to the means of production.     

我国东部沿海地区差距状况以及经济低谷地区的崛起

我国是区域发展差异巨大的大国之一，存在着多种尺度的区域发展差异。从中小尺工区域差异的角度，分析了我国东部沿海地区内部发展差距扩大趋势有其影响，可以看出，东部沿海地区在经济快速发展的同时，也存在着经济相对落后的低谷地区。沿海经济低谷地区分布相对集中于香港－－珠江三角洲、上海－长江三角洲、京津唐－环渤海三个经济隆起带之间，处于省际交界处。按照类型可以分为黄泛平原区、丘陵山区和沿海库区。东部经济低谷地区区位条件相对比较落后，交通可达性较差，产业结构单一，城市化水平发展严重滞后，社会经济发展比较缓慢，这些不利因素制约着该地区经济和社会的发展。根据崛起机制和途径，低谷地区发展呵以分为资源转换型、非国有经济推动型和外资推动型。建议国家修筑贯穿沿海经济低谷地区的东部沿海铁路大通道，降低沿海经济低谷地区设定标准，加快农业产业化发展，对特殊贫困地区实行特殊优惠政策，从而促进东部沿海地区经济协调发展。     

山区发展与特色经济研究--以湖北省恩施自治州为例

以湖北省恩施自治州为例，探讨了山区发展特色经济的重要途径。对其资源环境结构与产业结构作了对应分析，得出该区经济发展的优势在“山林”，而不在“耕地”，在地方“特色资源”，而不在“大众资源”。并采取经济区位商法，对本区众多资源进行了优势评价。根据其资源优势特点，指出恩施的优势在“山上”，应走以“绿色农业”为基础、以轻型加工业为主的发展道路，使本地区的经济结构由长期以来的一、二、三产业低位的传统排序逐步变为高层面的二、一、三的新排序。构建符合山区特色的产业结构。     

长江三角洲大都市周边地区城市定位研究——以苏州、南通为例

本文以大都市理论和区位理论为基础 ,从区域分工与协作的角度 ,探讨了在经济全球化和市场一体化背景下 ,上海大都市周边的大城市苏州和南通未来发展的城市定位以及实现定位的途径 ,为长江三角洲都市连绵区诸城市之间的协调发展提供借鉴。     

论北京城市建设的综合减灾问题

本文针对北京城市建设面临的自然与人为灾害背景,简要论述了北京地震、水灾、火灾及“新致灾源”的历史及现状,强调开展首都圈灾害研究及减灾规划设计的重要性,并提出了系统的减灾方略及相应的管理构想。     

基于GIS的东辽河流域生态安全空间差异评价研究

生态安全建设是协调经济开发与生态保护的重要战略.区域生态安全评价与预警研究具有空间特性、非线性、随机性,研究过程中必须处理大量的空间信息,而空间分析和空间数据管理正是GIS的优势,它使各环境要素的分布态势及彼此间的拓扑关系一目了然,并且图文并茂地展示全流域的生态安全格局.在充分研究辽河流域生态环境状况基础上,选取东辽河流域11个县市区,借助GIS格网赋值技术,讨论了基于GIS的东辽河生态安全空间差异的评价方法.首先,拟定"压力-状态-响应"(P-S-R)指标体系,实地调查并收集资料;然后,数字化流域,运用模糊AHP法赋权并量化计算;最后,建立东辽河流域生态安全指数GRID数据库,进行GIS的空间Interpolate运算和Assembly分析.结果表明,公主岭市是生态安全区,约占全流域面积的10.78%;西丰市和东辽县是生态不安全区,约占流域面积的13.07%;其余8个地区为生态安全中等区,约占全流域面积的76.15%.评价结果与各地区现状生态环境评价基本-致.提出了相应的生态保护建议.     

Detecting deterrence from patrol data

The threat posed to protected areas by the illegal killing of wildlife is countered principally by ranger patrols that aim to detect and deter potential offenders. Deterring poaching is a fundamental conservation objective, but its achievement is difficult to identify, especially when the prime source of information comes in the form of the patrols’ own records, which inevitably contain biases. The most common metric of deterrence is a plot of illegal activities detected per unit of patrol effort (CPUE) against patrol effort (CPUE-E). We devised a simple, mechanistic model of law breaking and law enforcement in which we simulated deterrence alongside exogenous changes in the frequency of offences under different temporal patterns of enforcement effort. The CPUE-E plots were not reliable indicators of deterrence. However, plots of change in CPUE over change in effort (ΔCPUE-ΔE) reliably identified deterrence, regardless of the temporal distribution of effort or any exogenous change in illegal activity levels as long as the time lag between patrol effort and subsequent behavioral change among offenders was approximately known. The ΔCPUE-ΔE plots offered a robust, simple metric for monitoring patrol effectiveness; were no more conceptually complicated than the basic CPUE-E plots; and required no specialist knowledge or software to produce. Our findings demonstrate the need to account for temporal autocorrelation in patrol data and to consider appropriate (and poaching-activity-specific) intervals for aggregation. They also reveal important gaps in understanding of deterrence in this context, especially the mechanisms by which it occurs. In practical applications, we recommend the use of ΔCPUE-ΔE plots in preference to other basic metrics and advise that deterrence should be suspected only if there is a clear negative slope. Distinct types of illegal activity should not be grouped together for analysis, especially if the signs of their occurrence have different persistence times in the environment.     

Boosting freshwater fish conservation with high-resolution distribution mapping across a large territory

The lack of high-resolution distribution maps for freshwater species across large extents fundamentally challenges biodiversity conservation worldwide. We devised a simple framework to delineate the distributions of freshwater fishes in a high-resolution drainage map based on stacked species distribution models and expert information. We applied this framework to the entire Chinese freshwater fish fauna (>1600 species) to examine high-resolution biodiversity patterns and reveal potential conflicts between freshwater biodiversity and anthropogenic disturbances. The correlations between spatial patterns of biodiversity facets (species richness, endemicity, and phylogenetic diversity) were all significant (r = 0.43–0.98, p < 0.001). Areas with high values of different biodiversity facets overlapped with anthropogenic disturbances. Existing protected areas (PAs), covering 22% of China's territory, protected 25–29% of fish habitats, 16–23% of species, and 30–31% of priority conservation areas. Moreover, 6–21% of the species were completely unprotected. These results suggest the need for extending the network of PAs to ensure the conservation of China's freshwater fishes and the goods and services they provide. Specifically, middle to low reaches of large rivers and their associated lakes from northeast to southwest China hosted the most diverse species assemblages and thus should be the target of future expansions of the network of PAs. More generally, our framework, which can be used to draw high-resolution freshwater biodiversity maps combining species occurrence data and expert knowledge on species distribution, provides an efficient way to design PAs regardless of the ecosystem, taxonomic group, or region considered.