Spatial-temporal dynamics of desert vegetation and its responses to climatic variations over the last three decades:a case study of Hexi region in Northwest China

Analysis of spatial-temporal variations of desert vegetation under the background of climate changes can provide references for ecological restoration in arid and semi-arid areas. In this study, we used the Global Inventory Modeling and Mapping Studies （GIMMS） NDVI data from 1982 to 2006 and Moderate Resolution Imaging Spectroradiometer （MODIS） NDVI data from 2000 to 2013 to reveal the dynamics of desert vegetation in Hexi region of Northwest China over the past three decades. We also used the annual temperature and precipitation data acquired from the Chinese meteorological stations to analyze the response of desert vegetation to climatic variations. The average value of NDVImax （the maximum NDVI during the growing season） for desert vegetation in Hexi region increased at the rate of 0.65x10-3/a （P〈0.05） from 1982 to 2013, and the significant increases of NDVImax mainly appeared in the typical desert vegetation areas. Vegetation was significantly improved in the lower reaches of Shule and Shiyang river basins, and the weighted mean center of desert vegetation mainly shifted toward the lower reaches of the two basins. Almost 95.32% of the total desert vegetation area showed positive correlation between NDVImax and annual precipitation, indicating that precipitation is the key factor for desert vegetation growth in the entire study area. Moreover, the areas with non-significant positive correlation between NDVImax and annual precipitation mainly located in the lower reaches of Shiyang and Shule river basins, this may be due to human activities. Only 7.64% of the desert vegetation showed significant positive correlation between NDVImax and annual precipitation in the Shule River Basin （an extremely arid area）, indicating that precipitation is not the most important factor for vegetation growth in this basin, and further studies are needed to investigate the mechanism for this phenomenon.

Soil Properties and Characteristics of Soil Aggregate in Marginal Farmlands of Oasis in the Middle of Hexi Corridor Region, Northwest China

The composition and stability of soil aggregate are closely related to soil quality, soil erosion, and agricultural sustainability. In this study, 49 soil samples at the 0-10 cm surface layer were collected from four soil types （i.e., Ari-Sandic Primosols, Calci-Orthic Aridosols, Siltigi-Otrthic Anthrosols, and Ustic Cambosols） in the marginal farmland in the oasis of the middle Hexi Corridor region and was used to determine the characteristics of soil aggregates. The composition of dry- and wet- sieved aggregates and the physical and chemical properties （including soil particle distribution, soil organic carbon （SOC）, calcium carbonate （CaCO3）, and oxides of Fe^3＋ and Al^3＋） of the selected soils were analyzed. The results show that soil particle size distribution is dominated by fine sand fraction in most of soils except Ustic Cambosols. Soil organic carbon concentration is 5.88 ± 2.52 g kg^-1 on average, ranging from 4.75 g kg^-1 in Ari-Sandic Primosols to 10.51 g kg^-1 in Ustic Cambosols. The soils have high calcium carbonate （CaCO3） concentration, ranging from 84.7 to 164.8 g kg^-1, which is increased with soil fine particle and organic carbon content. The percentage of 〉0.25 mm dry aggregates ranges from 65.2% in Ari-Sandic Primosols to 94.6% in Ustic Cambosols, and large dry blocky aggregates （〉5 mm） is dominant in all soils. The mean weight diameter of dry aggregates （DMWD） ranges from 3.2 mm to 5.5 mm. The percentage of 〉0.25 mm water-stable aggregate is from 23.8% to 45.4%. The percentage of aggregate destruction （PAD） is from 52.4% to 66.8%, which shows a weak aggregate stability. Ari-Sandic Primosols has the highest PAD. The distribution and characteristics of soil aggregates are in favor of controlling soil wind erosion. However, the stability of aggregate of all soils is weak and soils are prone to disperse and harden after irrigation. The mass of macro-aggregates and DMWD are positively significantly correlated with the contents of soil clay and silt, soil organic carbon （SOC）, CaCO3, and oxides of Fe^3＋ and Al^3＋. Soil fine silt and clay, SOC and CaCO3 are important agents of aggregation in this region, and the effect of SOC and CaCO3 on aggregate stability is more significant than that of soil silt and clay. Converting cropland to alfalfa forage land can increase SOC concentration, and in turn, enhance the formation of aggregates and stability. For the marginal farmlands in this fragile ecological area, converting cropland to alfalfa grassland or performing crop-grass rotation is an effective and basic strategy to improve soil structure and quality, to mitigate soil wind erosion, and to enhance oasis agricultural sustainability.

THOUGHTS ON CONSTRUCTING THE DEMONSTRATING AREAS OF THE ECOLOGICAL REBUILDING AND ECONOMIC SUSTAINABLE DEVELOPMENT IN HEXI REGION

Based on the field investigations, this paper analyzes systematically the achievements and problems of constructing the demonstrating areas of the ecological rebuilding and economic sustainable development in Hexi, Gansu Province, and then the thoughts on constructing the demonstrating areas are brought forward. It is considered that all kinds of ecological demonstrating areas should be merged in order to construct large scale characterized demonstrating areas which go beyond the district. In other words, in Hexi Region, Zhangye District should be constructed as the largest ecoagriculture demonstrating area of high technology; Wuwei District should be constructed as the largest ecological demonstrating area of agricultural comprehensive exploitation; JiuJia District, which is the shortened form of Jiuquan and Jiayuguan, should be constructed as the largest ecotourism demonstrating area; and Jinchang City should be constructed as the largest ecoindustry demonstrating area. At the same time, the constructing pattern should be selected according to the actual circumstances; science and technology should be applied to construct the demonstrating areas and accelerate the industrialization in the big market. Additionally, it is important to smooth the constructing system and implement the flexible and efficacious running mechanism, and it is suggested that the committee should be organized to administer the ecological demonstrating areas in Hexi Region.

Estimation Study of New Cancer Cases and Deaths in Wuwei, Hexi Corridor Region, China, 2018

Population-based cancer registration data were collected to estimate the cancer incidence and mortality in Wuwei, Hexi Corridor Region, China in 2018. We used the 2011-2013 data to predict the number of new cases and deaths in 2018 and the 2003-2013 data to analyze trends in cancer incidence and mortality. The goal is to enable cancer prevention and control directions. Our results indicated that stomach cancer is the most common cancer. For all cancers combined, the incidence and mortality rates showed significantly increasing trends（＋2.63% per year; P 〈 0.05 and ＋1.9% per year; P 〈 0.05）. This study revealed a significant cancer burden among the population of this area. Cancer screening and prevention should be performed after an epidemiological study of the cause of the cancer is completed.

Environmental Conditions of Barchan Dune and Barchan Chain-A Case Study from the Hexi Desert Area of Gansu

[Objective] The paper was to discuss why the top of tall barchan dunes and barchan chains widespread in single prevailing wind area had not been leveled by wind erosion. [Method] Based on the preliminary survey of distribution status,the morphological characteristics and environmental conditions of barchan dunes and barchan chains in Hexi desert area of Gansu were investigated in details. The significance of difference between samples and significance of correlation between indicators were examined via variance test. [Result] Barchan dunes and barchan chains in Hexi desert area of Gansu distributed at the leeward direction of desert fringe,generally in patch distribution. The distribution area was gravelly beach or cohesive gravel beach,with broader dune slack; winds in distribution area of barchan dunes and barchan chains blew obviously from one direction,while winds at other directions were light or occasionally strong but with low frequency;the barchan dune in the desert fringe of Hexi desert area of Gansu was relatively tall,while barchan chain was even more taller and larger. Coincidence or separation of the dune peak and the sand ridge might be related to distribution frequency of dominant prevailing wind or wind at opposite direction and the observation seasons.[Conclusion]Studying top stability of barchan dune has an important academic value in revealing blowing sand movement rule at desert fringe,invasion of sand flow,and expansion of desert.

Comparisons between Movement Speed of Main Types of Dunes:A Case Study of Desert Areas in Hexi Region of Gansu Province

In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.

Characteristics and Driving Forces of Spatial Expansion of Oasis Cities and Towns in Hexi Corridor, Gansu Province, China

This paper presents an integrated study of urban spatial expansion in the Hexi Corridor, Gansu Province, China based on TM, ETM remote sensing data in 1987, 1990, 1995, 2000, 2006 and 2011. The study explores the characteristics of urban spatial expansion and dynamic mechanism by using expansion speed index, expansion intensity index, compact index, fractal dimension, and extended flexibility index. We built the index system of influencing factors of urban spatial expansion by using the grey incidence model. The results showed that urban spatial expansion rate in the Hexi Corridor has been on the upward trend since 1987. Expansion intensity showed an obvious upward trend, however, the upward trend varied in different urban areas. In addition, the urban structure was loose relatively, but the urban compactness was more obvious. The urban spatial form tended to be simple, and the urban land use tended to become more intensive. Urban spatial expansion experienced several stages: padding internally, external expansion and padding internally. The main driving factors of urban spatial expansion are not the urban water resources and the oasis scale, but one or several factors such as economy, traffic, population, resource and national policy.

Regional Economic Types and Development Strategy of Small Towns in Suburb Beijing

The purpose of this article is to classify the regional economic types and development dynamics of small towns in suburb Beijing by applying the classification methods developed by Nelson's method and Location Quotient method into 183 small towns in Beijing.Four types of small towns are thus identified,including urban agriculture dominated towns,manufacturing dominated towns,service industry dominated towns and comprehensive type towns with balanced economic development.Within the environment of geographical information system,the spatial distribution pattern of four types of small towns with their evolution trend is analyzed.The results indicate that four types of small towns have obvious'core-periphery'spatial structure but with different functional orientations and evolution mechanisms.Based on this,the different development strategies for each type of small towns are summarized,providing a scientific reference for the differentiating planning and development strategies of these small towns.

Overall Image Design of Small Townships in Guangxi

Since the 21st century, the construction of small towns in Guangxi Zhuang Autonomous Region has been accelerated obviously and has already taken shape, but there are still some problems such as old towns not being well protected, new towns constructed in unified style, regional culture not being excavated and town features without characteristics. Thus, this paper analyzed some actual cases in Guangxi which are successful in designing the overall image of small towns, including Cendou Xincun, Xing'an County and Yangshuo Dongling, found that all constructions show rich elements of traditional houses, characteristics of local houses and distinctive cultures of folk houses, and concluded that tradition was the source to construct the features of small towns, innovation was the basis to develop small towns and culture was the core to sublimate the features of small towns. It was considered that traditional architectures could only be integrated with modern architectures by fully excavating cultural characteristics of regional architectures, combining with regional tourism industry and motivating local people to participate in reconstruction, to enhance local styles and national features, and create a beautiful, comfortable and harmonious living environment, so the overall regional styles and features of small towns can be represented and proceeded, comprehensive competitiveness and strong vitality can be given to those towns.

Urban River Landscape Design Based on Regional Characteristics——A Case Study of Jinxi River in Hushan Town

River is an important resource for human survival and development, and also a material carrier for cultural inheritance. In recent years, with the further urbanization of China, more efforts have been devoted in economic construction, but protection of local ecological pattern and inheritance of historic context have been overlooked. Taking landscape design of Jinxi River in Hushan Town for example, local resources were analyzed on the basis of regional characteristics to explore the future development trend. Colorful traditional cultures of south Fujian should be introduced into the design of waterfront landscapes, so historic and cultural elements of south Fujian will be inherited and demonstrated in new means by combining with modern landscape design techniques.

Urban Spatial Expansion Characteristics in China’s Rapid Urbanization Region—A Case Study of SXC Region

Urban spatial expansion characteristics are the responses of urbanization acts on the geographical space. Analyzing the characteristics can reveal the process of urban expansion and mechanism which is one of useful methods to find out the sustainable land use strategy balancing development and protection. In this paper, two main methods have been deployed in analyzing the spatial expansion characteristics of rapid urbanization region. One is the expansion index method and the other is fractal dimension method. And the results show that town-level urban sprawl has increased in a non-linear way since 1985, and even the increments of the urban expansion intensity are fluctuated. Morphology transformation from scatter to concentration is common phenomenon in the process of urbanization in the towns. From the morphology point of view, downtowns are more homogenous than towns with less variation. The concentration is the leading development trend in downtowns. And the more distance from the downtown is, the more spatial pattern morphology will be observed. These characteristics indicate that macro-scale policies of economic development and land use management have great impacts on the formation and characteristics of spatial patterns of urban dynamic patterns.

Research on central village selection in western underdeveloped region:a case study of Lidian Town,Jingning County,Gansu Province,China

Central village selection is the priority of small town construction.Depending on the development potential analysis,classification analysis,and quantitative and qualitative analysis,this article systematically proposes the specific methods of central village selection and also constructs the indicator system used in central village selection in small towns of western underdeveloped region in China.The article also puts forward ideas and methods for selection of central village in the western underdeveloped region through an empirical research on Lidian Town,Jingning County,Gansu Province.In the final part,suggestions and recommendations on how to develop central village for Lidian Town are made.

The Livability Perception of Residents in Rural Areas and Its Influencing Factors: A Case Study of Doumen Town of Zhuhai

Abstract The rural region is an important spatial unit for rural revitalization and urban-rural integration in the new era, strengthening the livability study has important practical significance for guiding the hard environment construction of rural regions. The evaluation index system of livability perception of residents in rural regions was constructed. Based on the questionnaire survey and in-depth interview of Doumen Town of Zhuhai City, this paper revealed the livability characteristics of rural residents and its influencing factors. The research showed that:① Residents of rural regions were quite satisfied with natural environment and built environment, but less satisfied with public service and infrastructure, and showed the social differentiation in livability perception;② The livability perception evaluation of rural residents was significantly affected by livable factors, showing the decreasing characteristics of “public service factors>social and humanistic environment factors>infrastructure factors>built environment factors>natural environment factors”;③ Individual and family attributes of rural residents were also important factors affecting their livability perception, but less important than the livable factors.

风景名胜区影响下的城镇建设与发展路径探析

风景名胜区是最具中国特色的一类保护地,多年来在保护资源并发展旅游的同时,带动了城镇建设发展。按照城市型、近郊型和独立型3种类型梳理244个国家级风景名胜区与城镇的关系,揭示风景名胜区带动城镇建设与发展的路径,即通过管控区内建设用地、划定外围保护地带、调整边界及布局旅游服务基地等规划措施,在防止自身被城市化的同时,促进相关城镇的空间建设、经济发展及职能转变。指明景城之间已形成相辅相成的关系,以期为新时期新需求下的保护地与城镇协调发展提供参考。

唐代中国西南边疆拓南、开南二城的建置考论

经过了天宝战争及随后的军事扩张,位于唐代中国西南边疆的南诏国在较短的时期先后建置了拓东、开南、镇西、宁北四个王国边境的重要治所城镇,其中开南城与拓南城的考释自元末以后已多现舛误,造成了史实混淆。事实上,唐代中国西南边疆的拓南城与开南城确为南诏国开拓建置的两座新城,而非“开南亦称拓南”,元末以后,“拓南”名号逐渐隐没于原地,同时被移置于“开南”地望,开始混用一起。厘清二城地望考释,不难发现拓南城的建置开拓了南诏国的西南辖境,开南城的建置开拓了南诏国的南境,从而把中原的“郡县制”文化辐射到了西南边境区域,客观上促进了区域内各民族的交往交流交融,奠定了唐代及后世中国西南边境、边界形成和发展的历史基础,为唐代中国西南边境区域各民族铸牢中华民族共同体意识做出了贡献。

区域视角下历史村镇集群区划与保护研究——以重庆欠发达地区为例

随着我国乡村振兴战略的全面推进,历史村镇保护作为实施乡村文化振兴的基础工作越发受到关注。目前城乡历史文化遗产保护理论虽日臻完善,但常规的孤点保护模式却难以解决偏远地区大数量历史村镇的保护问题。立足区域视角,在借鉴历史村镇保护相关理论实践的基础上,文章提出了定义、原则和任务三位一体的历史村镇集群区划理论架构。针对历史村镇集群划归的关键工作,选取重庆欠发达地区的72个历史村镇作为实证对象,依循“筛选集聚中心—构建区划体系—识别集群特性”的技术路径,构建了7大集群区划,并针对集群区内的村镇弱项从空间、产业和文化3大维度提出了适应性保护对策。

基于地域文化的青莲古镇视觉形象设计

青莲古镇的视觉形象是古镇对外彰显其形象和特色的重要因素之一。从地域文化与古镇视觉形象设计的互生关系入手,梳理青莲古镇地域文化,着力分析基于地域文化背景下的青莲古镇视觉形象设计,为城市的视觉形象设计提供新的思考维度和独特视角,是本文的旨趣所在。

黄土高原河谷城镇“川—沟”融合单元发展路径研究

通过分析黄土高原河谷城镇独特的城乡关系与发展困境,认为川道与次沟空间结构一体化、功能结构差异化发展是振兴黄土高原丘陵沟壑区的重要突破口,由此提出“川—沟”融合单元的概念内涵与划定方法。以榆林市绥德县为例,打破镇域行政边界和小流域镇村体系,基于川道城镇和次沟乡镇的空间关联关系划定10个融合单元,并从用地形态结构、产业经济地理、服务设施配置等方面对融合单元的空间构型、功能类型和服务水平进行剖析,探讨川道与次沟协同视角下以融合单元为抓手推动黄土高原河谷城镇高效发展和管控治理的新路径。

从“依形套式”到“循章衍法”:构形机理导引的历史城镇空间基因整体识别与活态传承

针对历史城镇空间基因识别、保护实践“有形无态、重式轻法”问题,提出构形机理导引的空间基因整体识别与活态传承方法。以“原型特征+构形机理”的显隐属性和“城镇格局、地块形态、街巷形式、建筑风貌”四重空间尺度为历史城镇空间基因要素解析框架,以“要素特征与结构特征同步提取”和“原型解构到显型建构机理延续”为操作路径,通过川渝地区历史城镇/街区实证研究,提出历史城镇格局结构要素与建构逻辑、地块图底肌理与聚合关系、街巷局域特征与系统节奏、建筑绝对形态与相对尺度同步提取的空间基因整体识别方法,以及城镇格局结构要素保控+基质空间重构、地块空间图底肌理修补+立体形态调节、街巷空间典型断面整饬+系统节奏保持、建筑空间异化风貌矫正+建构传统赓续的空间基因活态传承方法,以促进历史城镇空间基因保护实践从“依形套式”到“循章衍法”的路径转变。

气候变化和土地利用覆盖变化对河西地区植被净初级生产力的影响

河西地区不仅是我国重要的生态安全保护优先区,而且是丝绸之路经济带核心地段,开展该地区植被净初级生产力(NPP)评估及驱动力定量分析对于陆地生态系统与大气碳交换、气候变化与人类活动对植被综合作用等研究具有重要的理论价值和现实意义。基于MOD17A3产品数据、土地利用覆盖数据和气象数据,采用R-贡献率和偏相关分析方法,分析了2000—2020年河西地区植被NPP变化特征及土地利用覆被和气候变化对NPP的影响,结果表明:(1)河西地区耕地、水域和居民建筑用地面积整体呈增加趋势,而草地和未利用土地面积有所减少,且2010年后的土地利用覆盖变化(LUCC)整体动态度显著提高,其中,草地、耕地、建设用地和未利用地主导了土地利用类型的相互转换。(2)河西地区整体植被NPP呈增长趋势,2000—2010年和2010—2020年的变化斜率分别为0.86和1.29,且植被NPP具有明显的区域异质性,由东南向西北递减。(3)2000—2020年河西地区LUCC对植被NPP的影响逐渐增大,且气候变化对植被NPP的贡献率普遍高于LUCC,但二者对不同土地利用覆盖类型所起的作用不同,表现为耕地、林地和草地的植被NPP影响因子以气候变化为主导,未利用土地和居民建筑用地的植被NPP影响因子逐步以LUCC为主导。