京津冀地区耕地利用转型时空分异及驱动机制   总被引：2，自引：0，他引：2  

付慧  刘艳军  孙宏日  周国磊 《地理科学进展》2020,39(12):1985-1998

耕地利用转型代表耕地利用形态的趋势性变化。论文以京津冀地区157个县域空间为基本研究单元,从显性形态与隐性形态双重属性出发构建耕地利用形态指标体系,运用冷热点、空间变差函数等方法分析1990—2015年耕地利用形态变化的时空特征,在此基础上,利用空间误差模型(spatial error model, SEM)对耕地利用转型的驱动机制进行了定量分析。结果表明：① 京津冀地区耕地利用形态指数空间分布呈东南高、西北低的格局,与该地区地形分布格局基本一致,且因坝上高原特色农业发展形成独立高值区。② 京津冀地区耕地利用形态指数空间分异呈现逐渐缩小的趋势,显著热点区与显著冷点区分布相对稳定且面积不断缩小,耕地利用转型较为平稳。显性形态值普遍呈现先升高后降低趋势,隐性形态值则呈升高趋势,表明京津冀耕地出现空间收缩、功能优化式转型。③ 高程是影响京津冀地区耕地利用形态空间特征的主要自然环境因素,二三产业占比、地均固定资产投资与城镇化率等经济发展和城镇建设因素则是驱动1990—2015年京津冀地区耕地转型的主导因素,但不同时段、不同县域单元耕地转型动力机制存在差异,各驱动因子作用强度也不完全一致。  相似文献   

山地旅游小镇功能转型与重构的时空特征研究——-以黄山风景区汤口镇为例   总被引：1，自引：0，他引：1  

杨周  杨兴柱  朱跃  郑义刚 《山地学报》2020,38(1):118-131

山地旅游小镇是新时代乡村发展的重要类型,功能转型与空间重构是山地旅游小镇转型发展的核心内容之一。本研究采取参与式农村评估方法、GIS空间分析和高清遥感影像相结合的方法,以汤口镇为例,从微观尺度研究山区旅游乡村功能转型与空间重构的过程与格局。研究显示:(1)汤口镇生活功能由传统型向现代型转变,生产功能由农业主导型过渡到农旅融合型再向旅游主导型转变,生态功能由单一型向多元复合型转变。(2)旅游经济发达镇区相较于边缘乡村社区,旅居综合混质度较低。其中,旅游与居住时间分配相对均衡,宅屋空间倾斜于旅游,社群上融合度高,各区域间各混质维度存在差异。(3)汤口镇经历了旅游空间引入、生成、快速重构和导控更新4个重构阶段。该研究可为汤口镇村镇建设和旅游发展提供参考,也为下一步研究其转型发展的模式与机制奠定基础。  相似文献   

多重压力对重点生态功能区农户生计资产可得性的影响——以甘南黄河水源补给区为例   总被引：1，自引：1，他引：0  

高志玉  赵雪雁  兰海霞  石育中 《地理研究》2020,39(5):1152-1165

重点生态功能区主要承担着提供持续、稳定生态服务的功能,农户作为维护其主体功能的最基础单元和该区最主要的经济活动主体,面临着自然、社会、政策等多重压力,其交互作用不仅加剧了农户的生计脆弱性,更影响到该区主体功能的发挥,当前急需辨明多重压力对农户生计的影响,以便寻求有效的生计脆弱性减缓对策。本文以甘南黄河水源补给区为例,运用入户调查数据与有序Logistic回归模型等方法在识别农户遭受关键压力的基础上,进一步探讨生计压力的交互作用对生计资产可得性的影响。结果显示：① 甘南黄河水源补给区大多数农户遭受自然+经济型多重压力,其中,重点保护区、恢复治理区及经济示范区农户遭受的多重压力分别以自然+经济型、自然+经济型、经济+社会型为主。② 在多重压力的冲击下,重点保护区与恢复治理区农户除了社会资产可得性变化处于稳定状态,其余各类资产可得性变化几乎处于降低态势,而经济示范区农户的金融资产与社会资产的可得性变化处于稳定状态,其余各类资产可得性变化均处于降低态势。③ 婚嫁支出高与农牧产品价格下降、牲畜患病与人畜饮用水困难、子女学费支出高+婚嫁支出高+农牧产品价格下降+养老无保障、建房开支高与生态政策、子女就业困难与农业病虫害等压力的交互作用分别对自然资产、物质资产、金融资产、社会资产、人力资产等的可得性变化影响最强烈。  相似文献   

中国城市价值链功能分工及其影响因素     

盛科荣  王丽萍  孙威 《地理研究》2020,39(12):2763-2778

价值链的空间重组正在深刻的改变着城市体系的经济景观,建立在价值链分工基础上的城市功能结构的研究已经成为经济地理学的重要课题。将中国上市公司500强企业网络划分为公司总部、商务服务、研究开发、传统制造、现代制造、物流仓储和批发零售七种类型功能区块,研究了中国城市价值链功能分工及其影响因素。结果发现：沿着价值链的功能分工已经成为中国城市体系经济景观的显著特征,功能多样化城市和功能专业化城市并存于中国城市体系,东部地区和城市密集地区的城市在价值链分工中占据了更好的地位;中国城市按照价值链中的优势功能可以划分为九种类型,少数城市转变为承载公司总部、研究开发、商务服务等多样化功能的高等级中心城市,而大量中小城市则转变为传统制造专业化基地;市场潜力、关键资源、区位条件、营商环境等城市属性特征是城市功能分工的重要影响因素,城市资源、区位可达性等属性特征的增强将提高城市成为总部基地、商务中心和研究基地的概率,而降低城市成为传统制造基地的概率。  相似文献   

Spatial pattern formation of a ratio-dependent predator—prey model     

林望 《海洋学报(英文版)》2010,29(9)

This paper presents a theoretical analysis of evolutionary process that involves organisms distribution and their interaction of spatially distributed population with diffusion in a Holling-III ratio-dependent predator--prey model, the sufficient conditions for diffusion-driven instability with Neumann boundary conditions are obtained. Furthermore, it presents novel numerical evidence of time evolution of patterns controlled by diffusion in the model, and finds that the model dynamics exhibits complex pattern replication, and the pattern formation depends on the choice of the initial conditions. The ideas in this paper may provide a better understanding of the pattern formation in ecosystems.  相似文献   

Structural, electronic and optical properties of orthorhombic distorted perovskite TbMnO₃     

蔡鲁刚  刘发民  钟文武 《海洋学报(英文版)》2010,29(9)

This paper calculates the structural parameters, electronic and optical properties of orthorhombic distorted perovskite-type TbMnO₃ by first principles using density functional theory within the generalised gradient approximation. The calculated equilibrium lattice constants are in a reasonable agreement with theoretical and experimental data. The energy band structure, density of states and partial density of states of elements are obtained. Band structures show that TbMnO₃ is an indirect band gap between the O 2p states and Mn 3d states, and the band gap is of 0.48 eV agreeing with experimental result. Furthermore, the optical properties, including the dielectric function, absorption coefficient, optical reflectivity, refractive index and energy loss spectrum are calculated and analysed, showing that the TbMnO₃ is a promising dielectric material.  相似文献   

Structural, curvature and electronic properties of Rh adsorption on armchair single-walled carbon nanotube     

杨培芳  吴锋民  滕波涛  刘莎  蒋健中 《海洋学报(英文版)》2010,29(9)

This paper systematically studies the rolling effects of the (n, n) single-wall carbon nanotubes (SWCNT) with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs.  相似文献   

Altering intertidal sediment topography: effects on biodiversity and ecosystem functioning     

Diane Jones  & Chris L. J. Frid 《Marine Ecology》2009,30(S1):83-96

Sedimentary marine systems are often highly productive and perform important nutrient regeneration functions as they efficiently decompose organic material. In recent years the role of habitat effects and of species composition in ecosystem functioning has become of interest. Estuarine environments are frequently subject to considerable anthropogenic pressures whilst supporting a variety of habitats ranging from well sorted soft muds through biogenically stable sediments to highly mobile coarse sands. There is therefore considerable spatial complexity in habitat type and faunal composition. This study set out to observe the effects of altering the topographical habitat features of an estuarine mudflat on a range of porewater nutrient concentrations (NH₄⁺, NO₃⁻, NO₂⁻, PO₄³⁻ and SiO) collected from four depths (3, 5, 9, and 12 cm) and on faunal composition. Two treatments (Shelled Nets and Net Controls) were used to alter the topography from simple mud to a mussel shell crumble and were compared to un-manipulated Control areas. Sediment granulometry and organic matter content analyses alongside biological traits analysis of the fauna were also conducted.
Differences were observed in porewater nutrient concentrations between the Control and both netted treatments at 5 cm depth only; the species diversity and abundance were also different in the netted treatments compared to the Controls, although no difference between the two manipulated treatments were observed. The changes in faunal composition were attributed solely to the altered topography and the observed nutrient changes were attributed to the faunal alteration rather than the topographical manipulation.  相似文献   

海洋主体功能区划与海洋功能区划关系研究     

王倩  郭佩芳 《海洋湖沼通报》2009,(4)

开展海洋主体功能区划与海洋功能区划的关系和衔接研究,是保障两者在我国海洋事业中充分发挥各自作用的基础.本文从编制及实施2个方面理顺海洋主体功能区划与海洋功能区划的关系,促进两者在实际工作中的相互结合.  相似文献   

非线性Kuamoto-Sivashinsky方程的精确控制     

王水球 《成都信息工程学院学报》2009,24(3)

运用泛函分析性质以及Fourier变换的方法研究带有周期边界条件的非线性k-s方程在有限时间区间上的精确控制.首先研究线性化k-s方程的精确控制,证明对于任意给定的函数u0∈Hs,uT∈Hs,总能找到一个控制函数h使得线性化k-s方程有解u且满足u(x,0)=u0,u(x,T)=uT;然后结合线性化k-s方程的精确控制,通过定义Fredholm算子并应用Fredholm算子的一些理论找到非线性化k-s方程的控制函数,使其可精确控制.  相似文献