基于GIS和RS的沈阳城市潜在人口分布特征

基于QuickBird卫星影像,采用阴影长度法对城市居住建筑面积进行测算,结合社会经济统计数据对沈阳城市潜在人口分布特征进行分析.结果表明: 2015年,沈阳市三环内各行政区潜在人口分布不均;三环内潜在人口空间分布呈现典型的圈层结构特征;各行政区潜在人口数量为铁西区＞沈河区＞皇姑区＞于洪区＞和平区＞大东区＞东陵区;各行政区潜在人口密度为铁西区＞和平区＞沈河区＞皇姑区＞于洪区＞大东区＞东陵区;城市西部潜在人口密度高于东部,南部高于北部.居住建筑及人口的空间分布与区域的自然条件、经济状况以及基础设施建设等因素紧密相关.在未来城市规划建设中,应考虑加强铁西区以及中心城区的基础设施建设,适当增加公园绿地数量,合理开发城市南部的居住用地,适当控制居住人口数量,避免造成较大的环境压力.     

基于QuickBird和GIS的沈阳市城市潜在人口空间分布特征

人口是城市发展中最活跃的因素,了解城市人口分布特征对制定城市政策及城市各项设施规划布局具有重要意义.本文基于QuickBird卫星影像提取城市居住建筑信息,结合社会经济统计数据对沈阳市三环以内人口空间分布的特征进行分析.结果表明:2010年沈阳市三环以内各居住用地建筑类型的人口密度依次为:高层片块＞混合片块＞混合花园＞老式多层＞高层花园＞多层片块＞多层花园＞别墅片块＞矮房及棚户＞别墅花园;三环内居住建筑空置率高达30％以上,房地产市场存在严重过剩;沈河区的潜在人口密度在城市5区中最大,铁西区和大东区较小.基于人口重心分析测算的城市人口重心及各行政区人口重心为城市商业设施选址及基础设施规划提供了重要的参考信息.     

Predicting forest grouse distribution taking account of spatial autocorrelation

Spatially explicit, multi-scale models for predictions of species potential distribution can be useful tools for integrating biodiversity considerations in planning and strategic environmental assessment. In such models, the occurrences of focal species are related to habitat and landscape variables, which in urbanising areas should also include effects of urban disturbances. Moreover, the accuracy of the spatial predictive models may be affected by spatial autocorrelation, which means that a part of the variance is explained by neighbouring values. The aim of this study was to explore the effects of habitat and disturbance patterns on the distribution of two forest grouse species, Tetrao urogallus and Bonasa bonasia, and to detect and model the effects of spatial autocorrelation. The distribution of the two species could be explained in terms of reduction of a main predator, habitat quality, quantity and connectivity, including urban disturbances. The residuals of the initial regressions showed positive spatial autocorrelation that could be quantified by using a spatial probit model. The application of the spatial probit model revealed strongly significant spatial dependencies for both species. Furthermore, the model fit could be increased for T. urogallus by applying this model. The results implied that both species distributions might be affected by both reactions to the underlying land-use pattern, but also by interaction with neighbours. The use of the spatial probit model is a way to incorporate spatial interactions that otherwise cannot be captured by the independent variables.     

Applying the results of ecological studies to land-use policies and practices

Summary

• 1. 

  Good progress has been made in bringing the importance of high-nature-conservation-value farming systems to the attention of a wider audience. However, simply having a broad appreciation of which farming systems are good for certain species or species assemblages is of little use without a detailed understanding of how each particular farming system functions and integrates with the species reliant upon that system as a whole.
• 2. 

  Many species have intimate and complex interactions with the annual farming cycle, and their presence on any one piece of farmland is determined not only by the farm management occurring at that time but also by the management practised over the previous weeks and months. Since their exact farm management requirements are not fully understood, it would currently be difficult (if not impossible) to put in place the exact set of conditions necessary to ensure the continued occurrence of many desired species.
• 3. 

  Consequently, a detailed understanding of the ecological relationships involved is essential before advice can be provided on how best to develop any individual farming system (and the associated policies) so that the ecological characteristics of the system of value to the wildlife assemblages are maintained.
• 4. 

  These issues are highlighted and illustrated with reference to the findings from research into the ecology and requirements of the chough Pyrrhocorax pyrrhocorax and the effects of farm management practices on ground beetles (Coleoptera: Carabidae) and leatherjackets (Diptera: Tipulidae), which together can form important prey items for birds associated with grassland habitats.

     

Can traits predict species' vulnerability? A test with farmland passerines in two continents

Species' traits have been used both to explain and, increasingly, to predict species' vulnerability. Trait-based comparative analyses allow mechanisms causing vulnerability to be inferred and, ideally, conservation effort to be focused efficiently and effectively. However, empirical evidence of the predictive ability of trait-based approaches is largely wanting. I tested the predictive power of trait-based analyses on geographically replicated datasets of farmland bird population trends. I related the traits of farmland passerines with their long-term trends in abundance (an assessment of their response to agricultural intensification) in eight regions in two continents. These analyses successfully identified explanatory relationships in the regions, specifically: species faring badly tended to be medium-sized, had relatively short incubation and fledging periods, were longer distant migrants, had small relative brain sizes and were farmland specialists. Despite this, the models had poor ability to predict species' vulnerability in one region from trait-population trend relationships from a different region. In many cases, the explained variation was low (median R(2) = 8%). The low predictive ability of trait-based analyses must therefore be considered if such trait-based models are used to inform conservation priorities.     

Population and agricultural intensity in the humid tropics

A review of models of agricultural intensification and their application to the agricultural systems of the humid tropics is presented. Taken into account are the distributions of these systems at various population densities, available data on labor efficiencies, the costs of establishing continuous cropping, and data regarding soils under cultivation and various types of fallow. The findings that fallows much longer than 10 or 15 years serve no known agronomic function, that given preindustrial technology, grass fallows are disadvantageous, even environmentally destructive, and that continuous cropping usually entails a considerable amount of environmental modification support the interpretations that agricultural intensification in the humid tropics is best understood in terms of ecologically optimal strategies at different population densities. Points needing further investigation are highlighted: the reasons for very long fallows, and the comparative labor efficiencies of fallow and continuous cropping systems where crops and environments are similar.     

What drives the positive correlation between human population density and bird species richness in Australia?

Aim To test six hypotheses that could explain or mediate the positive correlation between human population density (HPD) and bird species richness while controlling for biased sampling effort. These hypotheses were labelled as follows: productivity (net primary productivity, NPP); inherent heterogeneity (diversity of vegetation types); anthropogenic heterogeneity (diversity of land uses); conservation policy (proportion of conservation land); increased productivity (human‐induced productivity increases); and the reduced‐slope hypothesis (which predicts that humans have a negative impact on species numbers across the full range of variation in HPD). Location Australia. Methods All data were collected at a spatial resolution of 1° across mainland Australia. Bird species richness was from 2007 atlas data and random subsampling was used to account for biased sampling effort. HPD was from the 2006 census. All other data were from government produced geographic information system layers. The most important biotic or abiotic factors influencing patterns in both species richness and HPD were assessed using simultaneous autoregressive models and an information theoretic approach. Results NPP appeared to be one of the main factors driving spatial congruence between bird species richness and HPD. Inherent habitat heterogeneity was weakly related to richness and HPD, although an interaction between heterogeneity and NPP indicated that the former may be an important determinant of species richness in low‐productivity regions. There was little evidence that anthropogenic landscape heterogeneity or human‐induced changes in productivity influenced the relationship between species richness and HPD, but conservation policy appeared to act as an important mediating factor and species richness was positively related to the proportion of conservation land only in regions of high HPD. Main conclusions The spatial congruence between bird species richness and HPD occurs because both respond positively to productivity and, in certain circumstances, habitat heterogeneity. Our results suggest that conservation policy could mediate this relationship, but further research is required to determine the importance of conservation reserves in supporting species in regions densely populated by humans.