甘肃酒泉荒漠戈壁灌木群落优势物种生态位特征

了解物种利用资源和占据生态空间的能力，对维持完善和科学保育荒漠戈壁植物群落的多样性具有重要意义。在综合反映各生态因子作用的群落类型和海拔梯度组合而成的两条资源轴上，测度分析了甘肃酒泉荒漠戈壁灌木群落主要优势种的生态位特征。结果表明：(1)在群落类型和海拔梯度两条资源轴上，红砂（Reaumuria songarica）、泡泡刺（Nitraria sphaerocarpa）和合头草（Sympegma regelii）的重要值和生态位宽度均较大，说明这些物种适应能力强,能够较好地利用环境资源，分布范围大，作为荒漠戈壁灌木群落中的广域种具有重要的生态地位和作用。(2)荒漠戈壁优势物种间的生态位重叠值多数较小，在群落类型和海拔梯度资源轴上生态位重叠值小于0.5的分别占总种对的62.63%和77.89%。生态位宽度大的物种之间一般生态位重叠值较高，物种利用资源能力强且存在竞争关系；然而，生态位宽度较小的物种与其他物种之间的生态位重叠程度较低，不同物种在环境资源的需求上产生互补，可以和谐共存；生态位宽度小的物种之间生态位重叠值仍较高，物种分布呈斑块现象；因此，生态位重叠与生态位宽度之间无显著相关性。(3)荒漠戈壁优势物种间总体表现为不显著的正关联，表明该植被群落结构及其物种之间处于稳定共存的状态。     

A case study on Landscape Component Niche based on Landscape Pattern Indices: Yanchi,Ningxia Province,China

Yanchi County is located in the agro-pastoral ecotone and belongs to the ecologically fragile area of Northwest China.It is important to study the evolution of landscape pattern to curb its environmental degradation.In order to intuitively show how the landscape pattern of the study area changes over time,Landsat Thematic Mappers(TM)and Landsat Operational Land Imager(OLI)data of 1991,2000,2010 and 2017 were used.This paper attempts to apply niche theories and methods into landscape ecology,and constructs a niche model of landscape components by using"n-dimentional hypervolume niche theory"and landscape pattern indices.By evaluating the spatial and temporal evolution of niche from the perspective of two-dimensional space to reflect the changes of landscape pattern in the study area over the past 26 years,new theories and methods were introduced for the characterization of landscape pattern.The results indicate that:1)The larger the attribute and dominance value of landscape components,the higher the ecological niche and the stronger the control effect on the overall landscape.2)The ecological niche of each landscape component was significantly different,just as its control effect on the overall landscape.3)The dynamic change of the ecological niche of each landscape component was different,with grassland,unused land and arable land always in a high dominant position,although the ecological niche of construction land and water area was always low.In general,the introduction of niche theory into the landscape ecology provided a new method to study the changes in regional landscape pattern.     

Genetic Diversity in Marine Molluscs: A Test of the Niche-Width Variation Hypothesis

Abstract. A test of the niche width variation hypothesis was conducted in the three Mediterranean littoral species of the family Trochidae: Monodonta turbinata, M. turbiformis and Gibbula richardi. Allozymic variation encoded by 26 gene loci was analyzed, and the levels of polymorphism (P), heterozygosity (H) and allele diversity per locus (A) were estimated and appear to support the niche-width variation hypothesis. The broad-niche species, M. turbiformis and G. richardi are more polymorphic and heterozygous than the relatively narrow-niche M. turbinata (P = 0.571; 0.731 and 0.417; H = 0.108; 0.116 and 0.078; A = 2.025; 2.489 and 1.965, respectively).     

Spatio-temporal differentiation of landscape ecological niche in western ecological frangible region: A case study of Yan’an region in northwestern China

In this study, we attempt to put forward a conception of landscape ecological niche, enlightened by international scholars on extending the ecological niche theory from spatial niche to functional niche. That is helpful for comprehensively appraising landscape spatial patterns and ecological functions, also, presents a new method for analyzing landscape fea-tures from multidimensional aspects. The practice process is demonstrated by taking Yan’an region in northwestern China as a case. Firstly, the indices system including spatial attribute and functional attribute is established for assessing landscape ecological niche. Additionally, two-dimensional figures are drawn for comparing the spatio-temporal features of landscape ecological niche in 1987 and 2000 among the 13 administrative counties. The results show that from 1987 to 2000, towards Yan’an region, spatial attribute value of landscape ecological niche changes from 1.000 to 1.178 with an obvious increment, and functional attribute value changes from 0.989 to 1.069 with a little increment, both of which enhance the regional landscape ecological niche. Towards each county, spatial attribute value of landscape eco-logical niche increases to different extent while functional attribute value changes dissimilarly with an increment or a decrement.     

Spatio-temporal differentiation of landscape ecological niche in western ecological frangible region： A case study of Yan＇an region in northwestern China

In this study, we attempt to put forward a conception of landscape ecological niche, enlightened by international scholars on extending the ecological niche theory from spatial niche to functional niche. That is helpful for comprehensively appraising landscape spatial patterns and ecological functions, also, presents a new method for analyzing landscape features from multidimensional aspects. The practice process is demonstrated by taking Yan＇an region in northwestern China as a case. Firstly, the indices system including spatial attribute and functional attribute is established for assessing landscape ecological niche. Additionally, two-dimensional figures are drawn for comparing the spatio-temporal features of landscape ecological niche in 1987 and 2000 among the 13 administrative counties. The results show that from 1987 to 2000, towards Yan＇an region, spatial attribute value of landscape ecological niche changes from 1.000 to 1.178 with an obvious increment, and functional attribute value changes from 0.989 to 1.069 with a little increment, both of which enhance the regional landscape ecological niche. Towards each county, spatial attribute value of landscape ecological niche increases to different extent while functional attribute value changes dissimilarly with an increment or a decrement.     

中国西部生态脆弱地区景观生态位的时空差异——以陕北延安地区为例

In this study, we attempt to put forward a conception of landscape ecological niche, enlightened by international scholars on extending the ecological niche theory from spatial niche to functional niche. That is helpful for comprehensively appraising landscape spatial patterns and ecological functions, also, presents a new method for analyzing landscape features from multidimensional aspects. The practice process is demonstrated by taking Yan’an region in northwestern China as a case. Firstly, the indices system including spatial attribute and functional attribute is established for assessing landscape ecological niche. Additionally, two-dimensional figures are drawn for comparing the spatio-temporal features of landscape ecological niche in 1987 and 2000 among the 13 administrative counties. The results show that from 1987 to 2000, towards Yan’an region, spatial attribute value of landscape ecological niche changes from 1.000 to 1.178 with an obvious increment, and functional attribute value changes from 0.989 to 1.069 with a little increment, both of which enhance the regional landscape ecological niche. Towards each county, spatial attribute value of landscape ecological niche increases to different extent while functional attribute value changes dissimilarly with an increment or a decrement.     

基于微观视角的农村居民点发展评价与布局优化——以陕西省重点示范镇沙河子镇为例

将生态位态势理论应用于农村居民点布局研究,从发展水平和发展潜力两方面选取指标分别作为发展"态"和发展"势"的评价因素,构建农村居民点发展评价模型,对居民点的发展实力划分等级。然后结合加权Voronoi图,明确各发展等级居民点的搬迁去向,从而实现全镇整治分区规划。沙河子镇农村居民点的发展实力可划分为高、中、低和不适宜发展4个等级;农村居民点整体发展较好,高、中发展实力级的居民点用地面积为304.07hm2,占全区的84.23%;具有明显的地形分异特征,其发展等级呈现由中部向南北两侧递减的趋势;全镇以农村居民点城镇化为整理重点,划分为城镇化区、优先发展区、改造发展区和控制发展区4种整治分区。结合生态位态势理论和加权Voronoi图的农村居民点合理布局研究具有较强的现实指导意义。     

Land use changes and sea level rise may induce a “coastal squeeze” on the coasts of Veracruz,Mexico

“Coastal squeeze” refers to the process in which coastal ecosystems are threatened by the combination of sea level rise (SLR) and the presence of a physical barrier, such as human infrastructure. This situation prevents the landward migration of ecosystems and species, as the coastline moves inland, and they are thus exposed to local extinction. Our objective was to explore coastal squeeze in the state of Veracruz, Mexico, through the study of urban expansion on the coast, an analysis of coastline geodynamics, and a projection of the potential effect of SLR on the distribution of two focal plant species which are endemic to the coastal dunes of Mexico. Urbanization of the coast, parallel to the shoreline, has been taking place increasingly rapidly, displacing ecosystems, both natural (mangroves, beaches and coastal dunes) and transformed (cultivated fields and pastures). Taking into consideration the geodynamic trends of the coastline and an analysis of its historical evolution, it can be seen that the coastal strip is eroding at rates that vary from slow to very rapid. Finally, the results of ecological niche modeling indicate that, under scenarios of SLR, the potential distribution of the two focal species would diminish: Chamaecrista chamaecristoides by 6–28%, and Palafoxia lindenii by 2–15%. These results indicate that “coastal squeeze” is likely in the study area, and that measures to limit or mitigate this process are required. Such measures could include urbanization programs which limit development to appropriate zones, the restoration and rehabilitation of deteriorated ecosystems and the conservation of those ecosystems which are still healthy.     

Analysis of coprolites from the extinct mountain goat Myotragus balearicus

Humans colonized the Balearic Islands 5–4 ka ago. They arrived in a uniquely adapted ecosystem with the Balearic mountain goat Myotragus balearicus (Bovidae, Antilopinae, Caprini) as the only large mammal. This mammal went extinct rapidly after human arrival. Several hypotheses have been proposed to explain the extinction of M. balearicus. For the present study ancient DNA analysis (Sanger sequencing, Roche-454, Ion Torrent), and pollen and macrofossil analyses were performed on preserved coprolites from M. balearicus, providing information on its diet and paleo-environment. The information retrieved shows that M. balearicus was heavily dependent on the Balearic box species Buxus balearica during at least part of the year, and that it was most probably a browser. Hindcast ecological niche modelling of B. balearica shows that local distribution of this plant species was affected by climate changes. This suggests that the extinction of M. balearicus can be related to the decline and regional extinction of a plant species that formed a major component of its diet. The vegetation change is thought to be caused by increased aridity occurring throughout the Mediterranean. Previous hypotheses relating the extinction of M. balearicus directly to the arrival of humans on the islands must therefore be adjusted.