Restoration of palatable grasses: A study case in degraded rangelands of central Argentina

Restoration of palatable grasses on degraded rangelands dominated by unpalatable grasses in central Argentina is limited by low availability of seeds and safe sites for seedling establishment. The objective of our study was to determine how mechanical disturbance of unpalatable grasses (Stipa spp.) in combination with seeding of a palatable grass (Poa ligularis) influenced species composition in a degraded rangeland excluded from livestock grazing. In April 2001 10 blocks were uniformly distributed on a previously burned site dominated by unpalatable grasses, and treatments applied in 8 m×8 m experimental plots. Treatments were ‘disked and seeded’ and control (no disking, no seeding). Perennial plant cover and end-of-season standing crop, at species or species group level, were assessed in December 2002/2003 and in December 2004/2006, respectively. P. ligularis out-competed both tillers of unpalatable grasses that survived mechanical disturbance and seedlings of unpalatable grasses established after mechanical disturbance. The cover and end-of-season standing crop of unpalatable grasses was higher in the control than in the ‘disked and seeded’ treatment, whereas the cover and end-of-season standing crop of P. ligularis was higher in the latter than in the former treatment. Our results suggest that a rapid transition from a state dominated by unpalatable grasses to a state dominated by palatable grasses can be achieved by mechanical disturbance of unpalatable grasses in combination with seeding of palatable grasses in semiarid rangelands of central Argentina.     

Effects of overgrazing and rainfall variability on the dynamics of semiarid banded vegetation patterns: A simulation study with cellular automata

The effects of factors acting at small scale (grass/grass and grass/shrub biological interactions) and landscape scale (overgrazing and rainfall changes) on the development and permanence of banded vegetation patterns (VB) are assessed with a spatially explicit cellular automaton model. In particular, the influence of two environmental factors that are changing in many VB arid lands (rainfall and grazing pressures) is studied. Three rainfall regimes (representing 0.5, 1.0, and 2.0 times the long-term rainfall average), five grazing intensities, two types (reversible and irreversible) of grazing disturbance, two grazing periodicities (chronic and pulse), two levels of grass colonization ability, positive and negative interactions between shrubs and grasses, and the efficiency of endozoochorous seed dispersal are simulated.The results show that the permanence of undisturbed VB depends on the interaction of two factors, rainfall regime and grass colonization ability. Type and intensity of grazing also modify VB cover and permanence; furthermore, long-term overgrazing may convert mixed grass/shrub plant communities to pure scrublands dominated by endozoochorous-dispersed shrubs due to competitive interactions between shrubs and grasses.Besides providing an adequate representation of the system’s dynamics, the model is a useful tool that may be used to explore the consequences of climate change on management scenarios.     

The replacement of arborescent cactus species along a climatic gradient in the southern Chihuahuan Desert: competitive hierarchies and response to freezing temperatures

In the southern region of the southern Chihuahuan Desert three common species of arborescent cacti are distributed over a north-west to south-east climatic gradient; Opuntia leucotricha, O. streptacantha, and Myrtillocactus geometrizans. In general, O. leucotricha is more abundant in the colder north-west section; M. geometrizans in the warmer south-east zone, not occurring in the north-west; and O. streptacantha reaches its greatest abundance in the centre of the region. We studied the potential replacement process between the three species due to canopy interference as well as the effect of a disturbance, freezing temperature, on their survivorship. Canopy interference between adjacent individuals of M. geometrizans/O. streptacantha and O. streptacantha/O. leucotricha indicated a potential replacement sequence of O. leucotricha replaced by O. streptacantha which, in turn, is replaced by M. geometrizans. In contrast, the damage caused by an extreme low-temperature event hardly affected O. leucotricha. It did however cause severe damage to individuals of O. streptacantha in the north-west of its distribution with little or no damage to individuals in the more south-eastern populations studied. M. geometrizans had a similar pattern of damage to O. streptacantha over its range in the region but at each site where the two species occurred together, that damage was more severe. Our observations suggest that disturbance in the form of extreme freezing temperatures is the mechanism that limits the distribution of these three arborescent cacti in the southern Chihuahuan Desert and allows their co-existence regionally.     

社区尺度下流动人口聚居区空间识别与尺度效应——以北京市为例

以北京市为案例区,以土地利用与人口分布的同一性为基础,通过建立基于空间配置法的流动人口聚居区识别方法,实现了社区尺度流动人口聚居区的空间识别。在此基础上,对比街道尺度和社区尺度流动人口聚居区的识别结果,判断流动人口聚居区的空间尺度效应,探析流动人口聚居区空间尺度效应的形成原因,明确选择社区尺度作为识别空间单元的必要性。研究发现：基于空间配置法的社区尺度流动人口聚居区识别方法具有较高的准确度,能够有效识别案例区约90%的流动人口聚居区。流动人口聚居区具有显著的空间尺度效应,主要原因包括：较大空间尺度容易忽略区域内部社会空间差异、城乡分割的二元社会经济体制和高速城市化进程。研究结论将为流动人口聚居区系统化、精细化研究提供技术支撑和方法借鉴,为政府相关部门进行流动人口聚居区顶层制度设计提供科学依据。     

Annual growth rings of the shrub Anarthrophyllum rigidum across Patagonia: Interannual variations and relationships with climate

Annual growth rings are well-defined in some shrubby species distributed along the Patagonian steppe and provide useful information to identify the environmental factors that influence the radial growth of shrubs in the region. However, little is known about variations in ring width from these species and their relationships with local environment. In this paper we present 18 growth ring width chronologies covering the last 2–3 decades from the shrub Anarthrophyllum rigidum (Fabaceae) encompassing most of its natural range of distribution in Argentina. Interannual variations in growth were first analyzed collectively to identify common regional patterns. In addition, shrub growth at each site was compared with local climate records and site-specific characteristics. Based on a principal component analysis (PCA), sites were joined in four major groups related to the site proximity to the Andes (foothills versus Patagonian plateau) and latitude (north versus south Patagonia). The relatively similar percentage of PCA variance associated with each group reflects environmental differences among sites. Consistent with this observation, we noted large variability in the responses of the A. rigidum woody growth to regional climatic fluctuations. At most sites, this species is favored by abundant winter precipitation, warmer spring and autumn temperatures (controlling the duration of the growing season), cool summers, or a combination of these factors. However, deviations from these patterns are also recorded. Our study represents the first large-scale dendroclimatological analysis of a shrubby species in southern South America. The results presented here provide information on the main patterns and factors affecting the growth of A. rigidum in Patagonia, and may be useful for determining well-suited practices for management and conservation of this ubiquitous species.     

Topographical relief characteristics and its impact on population and economy: A case study of the mountainous area in western Henan,China

Topographical relief is a key factor that limits population distribution and economic development in mountainous areas. The limitation is especially apparent in the mountain-plain transition zone. Taking the transition zone between the Qinling Mountains and the North China Plain (i.e. the mountainous area in western Henan Province) as an example and based on the 200-m resolution DEM data, we used the mean change-point analysis to determine the optimal statistical unit for topographical relief, and thereafter extracted the relief degree. Taking the 1:100,000 land use data, township population and county-level industrial data, population and economic spatial models were constructed, and 200-m resolution grid population and economic density maps were generated. Afterwards, statistical analysis was carried out to quantitatively reveal the impact of topographical relief on population and economy. In addition, the impacts of other topographical factors were discussed. The results showed the following. (1) The relief degree in western Henan is generally low, where 58.6% of the regional topography does not exceed half the height of a reference mountain (relative elevation ≤250 m). Spatially, the relief degree is high in the west while low in the east, and high in the middle while low in the north and south. There is a positive correlation between relief degree and elevation, and a much stronger correlation between relief degree and slope. (2) The linear fitting degree between the population and economic validation data and the corresponding simulation data are 0.943 and 0.909, respectively, indicating that the spatialized results can reflect the actual population and economic distribution. (3) The impact of topographical relief on population and economy was stronger than that of other topographical factors. The relief degree showed a good logarithmic fit relationship with population density (0.911) and economic density (0.874). Specifically, 88.65% of the population lives in areas where the topographical relief is ≤0.5 and 88.03% of the gross regional product was from areas where the relief is ≤0.3. Compared with the population distribution, the economic development showed an obvious agglomeration trend towards low relief areas.     

环境整治与农业经营矛盾中的农户行为和行政调控——基于日本佐渡岛农户调查

随着我国经济的高速发展,生态环境问题越来越突出。在推进国内区域研究的同时,从微观的角度,研究发达国家面临的促进持续发展和保护环境的实际问题对完善我国区域发展理论和施政思路意义重大。本研究基于2006～2008年在日本佐渡岛的实地调研和深度访谈,揭示了政府推进朱鹳野生环境治理的过程中,农户农业经营条件的恶化以及农户的意识...     

青藏高原市域综合交通优势度评价及空间特征——以林芝市为例

青藏高原的特殊性长期约束着交通设施的建设与功能,科学评价其交通状况具有重要意义.论文以林芝市为例,考虑自然特征、多种交通方式及交通稳定性,构建综合交通优势度评价体系进行实证探讨.研究发现:①综合交通优势度以巴宜区、米林县、工布江达县得分较高,其中中心乡镇尤其明显,分别在内部交通功能、对外交通功能、区位优势度方面具有优势...     

Water balance and vegetation change in the Sahel: A case study at the watershed scale with an eco-hydrological model

The Sahel, a semiarid area set in a fragile context, has been undergoing dramatic climate and land-use changes since the middle of the 20th century. The effects of these changes on the water cycle are analyzed using a coupled eco-hydrological model at the scale of a small representative catchment. Three land cover situations, corresponding to the 1950, 1975, and 1992 states, are simulated with two contrasted rain seasons, to produce the respective and combined effects of these two factors on the catchment water balance. The latter is largely dominated by rain-season evapotranspiration, representing some 60–65% of annual rainfall for the wet year in the three land use situations, but over 85% for the dry year. In absolute terms, evapotranspiration appears more sensitive to land-use changes than to the climate, but with variations that remain below 10%. These evapotranspiration figures are corroborated by field observations. Relative runoff sensitivity is much higher, nearly in the same 1.5:1 ratio as the annual rainfall for the climate effect, and with an increase by a factor of about 2.6 for the land-use effect. Confronting long-term runoff and water table dynamics evidences a direct linkage between these two processes.     

中国城市用地与人口规模分布时空动态比较——以环渤海地区为例

复合1992-2012年DMSP/OLS稳定夜间灯光等多源遥感数据和统计数据,运用多种城市规模分布理论方法,对城市用地与人口规模分布时空演变特征进行系统比较。结果表明：环渤海地区城市用地规模增长速度明显快于城市人口规模增长速度,城市人口规模分布比城市用地规模分布更为均衡;城市用地规模呈首位型分布但首位优势在减弱,城市人口规模呈位次型分布但首位优势在增强;位序迅速上升的城市主要位于山东省和河北省,位序显著下降的城市主要位于辽宁省。环渤海地区城市规模空间分布呈显著的区域差异和空间极化特征,且城市用地规模分布空间特征比城市人口规模分布更为突出。研究结论可为优化区域城市空间开发格局、促进人地系统可持续发展提供参考。     

Analysis of city centrality based on entropy weight TOPSIS and population mobility: A case study of cities in the Yangtze River Economic Belt

Based on statistical data and population flow data for 2016,and using entropy weight TOPSIS and the obstacle degree model,the centrality of cities in the Yangtze River Economic Belt(YREB)together with the factors influencing centrality were measured.In addition,data for the population flow were used to analyze the relationships between cities and to verify centrality.The results showed that:(1)The pattern of centrality conforms closely to the pole-axis theory and the central geography theory.Two axes,corresponding to the Yangtze River and the Shanghai-Kunming railway line,interconnect cities of different classes.On the whole,the downstream cities have higher centrality,well-defined gradients and better development of city infrastructure compared with cities in the middle and upper reaches.(2)The economic scale and size of the population play a fundamental role in the centrality of cities,and other factors reflect differences due to different city classes.For most of the coastal cities or the capital cities in the central and western regions,factors that require long-term development such as industrial facilities,consumption,research and education provide the main competitive advantages.For cities that are lagging behind in development,transportation facilities,construction of infrastructure and fixed asset investment have become the main methods to achieve development and enhance competitiveness.(3)The mobility of city populations has a significant correlation with the centrality score,the correlation coefficients for the relationships between population mobility and centrality are all greater than 0.86(P<0.01).The population flow is mainly between high-class cities,or high-class and low-class cities,reflecting the high centrality and huge radiating effects of high-class cities.Furthermore,the cities in the YREB are closely linked to Guangdong and Beijing,reflecting the dominant economic status of Guangdong with its geographical proximity to the YREB and Beijing's enormous influence as the national political and cultural center,respectively.     

国家需求结构演变理论及其应用——以中俄北极合作为例

首先,提出国家需求概念,在总结国家需求结构及其演变特点的基础上,提出双边关系中国家需求结构演变的三个模型：相对稳定型、合作优化型、关系紧张型。认为国家需求和人的需求一样,存在由低层次向高层次跃升的演变趋势。“低层次需求得到满足”是需求层次升级的前提条件,但这种满足具有方向性、主观性、阶段性。其次,运用国家需求结构演变模型分析了中俄北极开发合作的地缘政治环境,提出了维持中俄北极合作良好态势的对策建议：美国是中俄北极合作发生变数的能动力量,妥善处理好中美关系是重中之重;政治互信是中俄北极合作的决定性因素,加强双方在国际关系理论研究领域的合作是行之有效的政策工具;提高合作项目的透明度,向国际社会分享项目对生态环境和原住民影响的相关数据;加强战略沟通扩大共同利益,维持与美国盟友的合作伙伴关系;作为非北极国家,中国应该坚持对北极事务“有所为有所不为”的原则。最后,本研究得出如下几点结论：国家需求结构演变理论能够解释西方国际关系理论三大学派的核心观点;双边国家需求结构演变模型关注国际关系发生突变的规律性;国家需求结构演变理论能够为不同层次不同规模国家制定外交政策提供理论参考。     

旅游影响下的地方音乐及其对地方的建构——以丽江古城为例

在旅游业发展影响下,丽江古城传统纳西古乐的主体地位迅速地被现代民谣音乐所取代。音乐是地方文化的重要组成部分,地方音乐的变化折射出地方文化的整体变迁。本文利用观察法、文本分析法对丽江古城的地方音乐形式、表达内容及展演场所进行调查,采用访谈法对音乐表演者、经营者与游客进行了深入的采访。研究发现：在旅游影响下,原本作为本地居民精神伴侣、融入在地方社会生活中的传统古乐转变为服务于游客的各类商业演艺活动,在场所和游客认同方面表现出“不得其所”的特征;而以现代民谣音乐为代表的流行音乐成为丽江古城的主流音乐形式,在丽江古城中“安适其位”。传统古乐建构了丽江古城的独特感,激发了游客的异乡感,现代民谣音乐更加渲染了丽江古城的“小资情调”,两种音乐均在游客的情感建构中起到了重要作用。研究旨在丰富旅游地文化变迁的研究视角,反思旅游与地方传统文化的关系,亦是对音乐与地方人地关系研究成果的有益拓展与补充。     

民间信仰载体的地域格局及其影响因素——以兰州市榆中县祠庙文化为例

以祠庙祭祀为主体且祠庙保存良好的民间信仰是甘肃陇中地区民间文化的重要组成。甘肃陇中地区的民间信仰具有很强的趋同性,本文以陇中地区的榆中县为例,以各村的祠庙为民间文化载体,通过核密度分析、Logistic回归等方法探讨榆中县民间文化载体的空间分布及其影响因素对于探讨陇中地区人地关系,保护和弘扬民俗文化有着重要意义。研究结果表明：（1）根据已有研究将榆中县民间信仰归纳为山神信仰、水神信仰、天地信仰、女性信仰、英雄崇拜和祖先崇拜,祖先崇拜的祠庙数量占有重要地位;（2）榆中县祠庙主要分布在西北黄河南岸、中部陇海铁路沿线及南部风景名胜集聚区,村级层面空间差异不显著、乡镇空间差异相对较大。通过核密度分析,不同类别民间信仰空间分布热点各有不同;（3）榆中县民间信仰空间分布受到区位条件限制,民间信仰的祠庙多位于海拔高度较低、人口密度较大、交通可达性较好的地区,坡度和到水源的距离成为山神信仰和水神信仰祠庙空间分布显著的影响因子,榆中县祠庙呈现出山神信仰类祠庙“依山”,水神信仰类祠庙“傍水”的空间特点。     

宁夏中部生态脆弱区土地利用变化及沙漠化响应——以宁夏盐池县为例

以宁夏中部生态脆弱区典型县为研究对象,利用1985、1995、2000年三期TM影像提取的土地利用数据,基于GIS空间统计分析功能,结合土地利用指数及分形模型、景观破碎度等景观分异测度指数,探讨近20年来该县土地利用时空分异特征及其沙漠化响应,结果表明:①土地利用变化整体上表现为中低覆盖度草场减少,林地为先破坏而后治理;②1985~2000年沙地扩展区域从北部风沙地貌区转移到中部波状高原区,尤其是扬黄灌渠附近需加强管理和防治;③草场沙化比例最大,中覆盖度草场沙化集中在北部农作活动密集区,其沙化斑块连通性强,低覆盖度草场沙化大部分紧临原沙地,受自然因素干扰更为明显;④中、低覆盖度草场斑块不稳定性程度较高,中覆盖度草场属该区域中对自然条件变化和人为干扰最为敏感的类型,需要加强管理和建立科学的生态恢复重建格局。     

华北平原“杨上粮下”现象的驱动机制——以河北省文安县为例

以Landsat5TM遥感影像、农户调查数据和统计数据为基础数据,运用3S技术提取了案例区河北省文安县1995～2007年土地利用变化信息,分析了杨树扩张的时空格局;并从农户杨树种植决策行为视角,运用数理统计、投入产出法分析了杨树扩张占地的驱动因素。结论如下:(1)杨树林地扩张幅度大、速率快。(2)杨树扩张所用土地92.14%来源于耕地,"杨上粮下"现象突出。(3)杨树扩张速率的空间差异显著。杨树扩张受生产要素、土地产品市场及政策因素的综合驱动,其中劳动力因素和经济因素起主要作用。(4)非农从业人员比率和农民年人均收入越高,杨树扩张速度越快。在劳动力由富余转为相对稀缺的情况下,农户为提高经济收益,倾向选择耗工少,劳动生产率较大的杨树,是杨树扩张占地的根本原因。     

Understanding the change of land space utilization efficiency with different functions and its coupling coordination: A case study of Urban Agglomeration in the Middle Reaches of the Yangtze River,China

Journal of Geographical Sciences - Land spaces function in capacities of urban development, agricultural production, and ecological conservation, among many others. Research of land space...     

基于融入-隔离双向对比的流动人口主观社会融合及其影响因素研究——以福厦泉城市群为例

基于2017年流动人口动态监测数据,选取福厦泉城市群,构建融入-隔离对比的指标体系,探讨了流动人口在流入地的主观社会融合及其影响因素。研究发现：① 流动人口在流入地的主观社会融合程度较高,但融入与隔离并存,且以融入为主。② 流动人口主观社会融合受流迁模式、社会网络、生计资本、制度政策和人口特征等因素综合影响：宏观上基本公共服务均等化能显著地增强融入、削弱隔离,淡化了户籍制度造成的融入障碍;中观上在流入地加强社会交往和积极参加组织活动、改善住房和提高收入确实有助于流动人口在流入地增强融入、减弱隔离,但基于流出地方向的土地预期收益、家庭困难及乡土依恋等主客观因素则增强了流动人口在流入地的主观隔离、削弱了主观融入;微观上近距离、长时段和家庭化迁移的流动人口主观融入程度较高,受教育程度的提高有助于流动人口削弱主观隔离,更好地融入流入地。研究认为应促进流动人口客观融合并使其与主观融合相匹配,改变以流动人口融入当前流入地实现市民化的单向思维,统筹考虑流入地与流出地的双向影响,将流动人口市民化工作重心由落户转向基本公共服务的无差别覆盖,实现流动人口从主观“愿意”到客观“能够”的社会融合。     

制度变迁下农垦城镇空间演化及其动力机制研究——以湖北省五三农场为例

制度变迁是城镇空间演化的重要驱动,农垦城镇作为一类特殊且重要的城镇类型,受制度因素影响更直接、更显著。鉴于现有研究较少基于制度变迁探究农垦城镇空间演化,论文系统梳理了农场制度变迁的总体情况,并以湖北省五三农场为例,采用综合研究方法,揭示了制度变迁下农垦城镇空间演化及其动力机制。研究发现：① 农垦城镇空间演化主要体现在空间形态、空间关系和功能结构3个方面,即空间形态从缓变到剧变,空间关系从生产协作关系转为城乡关系,功能结构不断从公办到私营、从生产主导到消费主导、从单一化到多元化;② 制度变迁通过改变农场身份、利益关系和资源配置推动农垦城镇空间演化,其中农场身份变化直接影响农垦城镇空间的发展方向,利益关系变化促使农垦城镇空间产业化、市场化,资源配置变化通过改变资源配置主体、类型、尺度和速度作用于农垦城镇空间演化。通过研究,以期能更有针对性地指导农垦城镇在新时期的发展,同时也可丰富城镇空间演化的理论内涵。