塔里木河中游主要植物种群的生态特征分析

根据新疆塔里木河中游植物样地的监测数据,计算了19种主要植物在土壤含水率与土壤盐分资源维上的生态位宽度及生态位重叠值,作出了反映它们相似程度的最小生成树图;探讨了19种植物的生态位特征及各物种在二维环境因子上的相似关系。结果表明:建群种对环境变化的生态适应性较强,在二维生态因子上的生态位宽度值较大,乔灌植物普遍具有较大的生态位宽度(个别物种除外),草本植物除建群种外生态位宽度相应较小,并对个别物种生态位的变化进行了分析。由于环境条件的影响和胁迫,塔里木河中游物种间的生态位重叠值普遍较低。根据最小生成树图分析了19种植物在二维环境因子上的生态相似关系     

Size‐based differences in isotopic niche width (δ13C and δ15N) of green turtles (Chelonia mydas) nesting on Príncipe Island,Gulf of Guinea

Within the same population, nesting green turtles (Chelonia mydas) might exploit different niches by exhibiting polymorphic foraging strategies and/or inhabiting geographically distinct foraging areas. This is crucial information for the conservation of this species. Here, we used stable carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) to test for differences in a population of green turtles nesting on Príncipe Island (1°37′N; 7°24?′E), Central Africa. A total of 60 nesting females were sampled on the two main nesting beaches of the island in December 2012. Minimum curved carapace length (CCL) was recorded, and δ¹³C and δ¹⁵N values were measured in the epidermis of each individual. Overall, CCL varied from 87.0 to 108.0 cm (mean ± SD =100.0 ± 5.1), δ¹³C values from ?19.4 to ?8.6‰ (?17.3 ± 1.8) and δ¹⁵N values from 7.9 to 17.3‰ (13.6 ± 1.5). Despite the large variation in both isotopic ratios, their distributions were unimodal, showing an absence of polymorphic foraging strategies and isotopically distinct foraging areas. However, smaller females (< median, 100.8 cm) occupied a much larger isotopic niche (i.e., four times greater) than larger females. These results suggest that nesting green turtles may forage opportunistically on the resources available in each of their foraging home ranges, with smaller females venturing to more isotopic‐diversified areas and/or exhibiting broader foraging strategies than larger females. In addition, and in accordance with other studies, findings suggest that the foraging grounds used by the Príncipe green turtle nesting females are distributed mainly throughout the Gulf of Guinea.     

Research on the Suitability Evaluation of the Development and Utilization of Regional Selenium-rich Soil Resources and Spatial Zoning based on Niche Theory

Relying on the advantages of selenium-rich soil resources, the development of special selenium-rich agricultural industry is an effective measure to implement the rural revitalization strategy. This paper took Yuanzhou district as the research area, based on ecological niche theory, creatively determines the dominant and limiting factors of selenium-rich soil resources development and utilization from three aspects of natural resources endowment, land use conditions and ecological protection, constructed the evaluation index system of selenium-rich soil resources development and utilization and ecological niche suitability index measurement model, and explored the suitability of regional selenium-rich soil resources development and utilization and zoning. The research results show that: (1) The area suitable for exploitation of selenium-rich soil resources in the study area is 174658.4 ha, accounting for 68.83% of the total area, mainly distributed around Yuan River and in the central, northern, northwestern and northeastern areas of the study area. (2) Based on the evaluation results of the suitability of selenium-rich soil resources development and utilization and the development of related agricultural industries, the study area was divided into four functional zones of selenium-rich industrial development: core zone, key zone, development zone and radiation zone. The core zone and key zone are suitable for building selenium-rich agricultural industry demonstration area and selenium-rich products breeding production base, and the development zone and radiation zone can vigorously develop selenium-rich modern agriculture and selenium-rich recreation tourism, which will accelerate the development trend of multi-level and diversified selenium-rich industry in study area.This study can provide scientific, reasonable and feasible ideas and methods for the development and utilization of selenium-rich soil resources and the planning and development of selenium-rich industries in similar areas.     

Effects of the invasive plant Lupinus polyphyllus on vertical accretion of fine sediment and nutrient availability in bars of the gravel-bed Paloma river

Floodplain vegetation is fundamental in fluvial systems, controlling river corridor geomorphology and ecology through a series of hydraulic, sedimentological, and biological processes. Changes caused by introduced plant species can thus result in shifts in river regime, succession trajectories and nutrient availability, affecting native biodiversity. The exotic bigleaf or marsh lupine Lupinus polyphyllus, introduced in Patagonia in the last decades, is aggressively invading fluvial corridors. It fills unoccupied ecological niches in southern Chilean rivers, due to its capacity for nitrogen fixation, its perennial habit, and high shoot density and leaf surface area.We investigated the effects of L. polyphyllus on vertical accretion of fine sediment, and soil carbon and nitrogen content, on gravel bars of the Paloma river, Chilean Patagonia, where lupine is believed to have been introduced in 1994. We sampled plot pairs with and without lupine, with each pair located at the same elevation above river stage, and plots distributed over the reach scale. We measured the thickness of the fine soil horizon, grain size distribution, and soil carbon and nitrogen content. We also compared aerial photographs to evaluate changes in spatial coverage of lupine along the study reach.Presence of lupine was strongly correlated with a thicker layer of finer sediment, in turn characterized by higher organic carbon, carbon to nitrogen ratio, and inorganic carbon content. Contrary to our expectations, we did not find any significant differences in total nitrogen. Aerial photographs did not reveal important differences in coverage between 2007 and 2010, but plant density appears to have increased between the two dates, and invaded gravel bars also appear to be more stable. Lupine dominance of otherwise sparsely vegetated gravel bars in Patagonian rivers appears to have greatest consequences on bar physical structure (increased rates of accretion of fines) and secondary repercussions on soil quality (increase in recalcitrant organic matter), with potential transient effects on nutrient availability (possible increased soil metabolism, followed by carbon mineralization and loss of lupine nitrogen subsidy).     

Not developed yet? Alternative ways to include locations without changes in land use change models

Biogeographers have developed a new generation of statistical models called presence-only models, which require no data concerning the absence of a species and do not assume that the absence of a species indicates habitat unsuitability. Both characteristics are especially useful when modeling a species that is actively spreading across a landscape. Although urban expansion is sometimes equated to an invading species, the applicability of presence-only models has not yet been explored when modeling urban growth. This article compares predictions of urban growth using a presence-only model (ecological niche factor analysis) and a more traditional presence–absence model (logistic regression). An additional model used pseudo-absence sites, from the presence-only model output, as input into the presence–absence model. The models were applied to New Jersey's Barnegat Bay Watershed. Overall, the traditional presence–absence model performed the best, although the presence-only model was sufficiently similar to warrant further exploration of presence-only models when no reliable absence data (i.e., locations where no conversion occurred) exists. However, due to data-formatting requirements of the presence-only model, it is difficult to accommodate data pertaining to administrative boundaries, which are inherently Boolean. Finally, the output based on the pseudo-absence approach overpredicted urban conversion when compared to the other approaches.     

Linking Home to Work: Ethnic Labor Market Concentration in the San Francisco Consolidated Metropolitan Area

Different perspectives have been offered to explain ethnic labor market concentrations. In most studies, however, residential places are seldom included in the research framework. Using data from 5% Public Used Microdata Samples in 2000, this case study of the San Francisco Bay Area reveals that the robust growth of the new economy is dramatically segmenting the geography of employment and thereby the spatial division of labor in each ethnic group. Living arrangements, such as central-city residence and living in coethnic-concentrated-PUMAs, increase the chances of niche employment for most racial/ethnic groups, even after controlling for human capital and certain local context factors. However, there is a "substitution" effect between personal socioeconomic status and location factors. This study argues that living arrangements can provide a mechanism through which personal characteristics, social networking, and ethnic recourses interact with macroeconomic trends, and thus carve out local labor market experiences across the urban space.     

Abiotic,residual and functional components of landforms

The concept of functional ecogeomorphology developed originally from the study of fluvial systems represents an insightful framework for describing landforms as structures adjusting to external physical forces, and also as functional components contributing to the complex play of interactions and reciprocal adjustments between biotic and abiotic elements of ecosystems. In this commentary we propose to extend the model of functional ecogeomorphology by classifying landforms in three fundamental components: abiotic, residual and functional. The various possible combinations of these three components are presented and discussed in the scope of evolutionary geomorphology. Copyright © 2010 John Wiley & Sons, Ltd.     

额济纳绿洲植物群落种间关系和生态位研究

根据61个天然植物群落样地的野外调查资料,采用生态位测度、方差比率法和基于2×2列联表的χ2检验、Ochiai关联指数、Pearson积矩相关系数和Spearman秩相关系数等方法,对额济纳绿洲植物群落主要物种进行了生态位和种间关联分析。结果表明：（1）胡杨（Populus euphratica）、柽柳（Tamarix ramosissima）、苦豆子（Sophora alopecuroide）生态位宽度值大,分别为该区的泛化种和乔木层、灌木层及草本层的优势种;（2）额济纳绿洲植物群落物种的总体联结性为不显著的正联结,大多数种对间呈中性联结（χ2<3.841,p>0.05）,物种趋向于独立分布。（3）种间联结系数（Ochiai指数）与生态位重叠之间极显著正相关,而生态位宽度与生态位重叠之间并无直接线性关系。     

土地利用变化的地形梯度特征与空间扩展——以北京市海淀区和延庆县为例

选择北京市海淀区、延庆县作为研究区,利用1992年、2002年遥感影像数据,借用地形位梯度指数,研究了土地利用变化的地形梯度特征及其空间扩展形势。研究表明:(1)海淀区建设用地受到经济和社会发展驱动明显,表现出既向低地形梯度位也向高地形梯度位扩展;但农业用地、果园因建设用地扩展受到挤压,表现为向更高地形位扩展态势;林地在高地形位得到了明显恢复,也有向更低的地形位扩张的趋势,但灌草地和未利用地在中高地形位受到林地挤压,低地形位受到农业用地、果园挤压,优势地形位明显萎缩;(2)延庆县建设用地扩展受地形位驱动作用明显,主要集中在低地形位区域;农业用地主要分布在较低地形位上,变化不大;果园在经济发展需求驱动下,向更高地形位扩展;林地在较高地形位得到较好恢复,对灌草地、未利用地产生了挤压作用,使得灌草地、未利用地在中高地形位的优势度降低,优势分布区间趋于萎缩。     

基于生态位理论的河北平原地下水开采潜力评价

传统的地下水开采潜力评价方法主要采用单个指标进行评价,难以全面科学地反映地下水开采潜力的影响要素。地下水的空间分布、动态变化受到经济社会发展、开采技术等多个因素影响,也与自身调节有关,这与生态位理论的观念吻合。文中提出地下水生态位的定义、计算公式;对河北平原9个主要城市进行地下水生态位计算、聚类分析,分析其地下水开采潜力;并与传统方法的评价结果进行对比。结果表明：除保定、秦皇岛和廊坊外,其他城市的两种方法的评价结果大致相似;差异分析说明地下水生态位的评价方法更全面、科学合理且符合实际。生态位理论将为地下水开采潜力评价分析提供一种新的、甚至是根本性的尝试。