地图线状要素自动注记的算法设计与实现

在地图自动注记的研究中,线状要素由于其形状复杂、灵活性大,难度较大,在注记自动研究问题中占有较大的比重。本文探讨了线状要素自动注记的问题,提出了一种解决线状要素自动注记问题的思路和方法。     

植物气候生态位及三维空间分布的图示化--以水青冈属为例

以水青冈属为例,应用多元统计分析方法和原理,借助计算机作图软件,实现了植物分布在综合气候因素中的直观表达,使不同物种的气候生态位的比较成为可能,应用空间统计学方法和原理,在计算机空间分析软件和作图功能的支持下,实现了植物三维空间分布的表达。     

Relative importance of estuarine nurseries for species of the genus Diplodus (Sparidae) along the Portuguese coast

The relative importance of estuarine nursery areas for species of the genus Diplodus and their relations with several environmental variables was evaluated along the Portuguese coast. Nine estuarine systems were sampled with beam trawl surveys. Species of the genus Diplodus were only present in estuaries south of the Ria de Aveiro (40°38′). A latitudinal gradient of increasing species richness and abundance towards the south was found. Estuarine nurseries of Diplodus vulgaris, Diplodus sargus and Diplodus puntazzo were characterized by mud substrate, lower salinity and lower dissolved oxygen, with the exception of Ria Formosa. Diplodus bellottii was associated with estuaries with large areas and high volumes, the Tejo and the Sado. Diplodus bellottii nursery grounds were characterized by low depth. Diplodus annularis was associated with seagrass and saltmarsh habitats, certainly because it is the only species of the genus Diplodus which recruits exclusively to seagrass meadows. Diplodus annularis nursery grounds were also characterized by sand substrate, higher salinity and higher dissolved oxygen. Niche breath varied widely amongst species and location. Diplodus vulgaris generally presented the highest values of niche breath, except when D. bellottii was present. Niche overlap was not high, the highest value being that between D. vulgaris and D. sargus in the Mira estuary, with 76% spatial niche overlap. Considerations were made on these species progress towards the north in a climate warming context, taking into account the habitat associations described here.     

龙门山北段观雾山组地层时代分布、沉积充填及其古地理意义

自四川盆地西北部(川西北)泥盆系观雾山组油气勘探取得重要进展以来,观雾山组的沉积储层研究受到了广泛重视。然而,由于观雾山组地层划分方案的变动和地层的穿时性,导致目前对观雾山组的时代分布和充填过程认识不清,从而影响了沉积古地理格局的恢复。本文以四川广元西北乡、潜溪河剖面泥盆系观雾山组牙形石生物地层研究为基础,结合区域古生物地层资料,认为江油马角坝以北的观雾山组绝大多数沉积于晚泥盆世早—中弗拉期,且地层沉积时间自南西向北东逐渐变晚。龙门山北段观雾山组具有自西向东、自南向北地层厚度减薄和地层时代变新的特征,表明来自扬子地台西部的古特提斯洋海水向东侵入龙门山地区,因地形差异和渐进式海侵形成了自南西向北东的超覆沉积。由于岩相分异,超覆沉积形成的观雾山组与金宝石组在区域上既表现为上下叠置关系,也表现为同期异相的相变关系。该研究不仅对约束川西北地区观雾山组地层时代提供了可靠的古生物证据,而且对认识龙门山地区泥盆系的充填过程、沉积古地理格局均具有重要意义。     

人工鱼礁区三种习见肉食性软体动物营养生态位研究

以小黑山岛人工鱼礁区为研究区,利用稳定同位素技术分析该海域三种习见肉食性软体动物长蛸（Octopus minor）、短蛸（Octopus fangsiao）和脉红螺（Papana venosa）的营养生态位,进而判断物种种间关系。分析结果显示：食物来源范围由大到小依次为长蛸、脉红螺、短蛸,其中长蛸食物来源包含短蛸食物来源范围,但脉红螺与两种蛸类食物来源无交叉;营养级由高到低依次为长蛸、短蛸、脉红螺。长蛸与短蛸营养生态位重叠比例较高,存在明显的竞争关系,与短蛸相比,长蛸营养级更高,食物来源范围更广,在竞争中处于优势地位;脉红螺的营养生态位与两种蛸类无重叠,其营养级比两种蛸类更低且无捕食或竞争关系。     

长江下游沿江湿地升金湖越冬水鸟觅食集团结构及生态位特征

集团结构和生态位特征是量化动物群落组织过程的重要指标,鸟类集团结构及其食物资源分割的分析对于理解群落中不同鸟种生态适应性具有重要意义.越冬水鸟集团结构和生态位特征取决于食物资源的丰富度和可获得性.本文通过对升金湖越冬水鸟的觅食生境和觅食行为的观察,对水鸟群落的集团结构进行划分,采用Levins指数和Pianka指数计算...     

The existence of a chaotic region due to the overlap of secular resonances ν5 and ν6

A nonlinear theory of secular resonances is developed. Both terms corresponding to secular resonances ₅ and ₆ are taken into account in the Hamiltonian. The simple overlap criterion is applied and the condition for the overlap of these resonances is found. It is shown that in given approximation the value p = (1 - e²)^1/2(1 - cosI) is an integral of motion, where the mean eccentricity e and mean inclination I are obtained by eliminating short-period perturbations as well as the nonresonant terms from the planets. The overlap criterion yields a critical value of parameter p depending on the semi-major axis a of the asteroid. For p greater than the critical value, resonance overlap occurs and chaotic motion has to be expected. A mapping is presented for fast calculation of the trajectories. The results are illustrated by level curves in surfaces of section method.     

Partitioning of temperature resources amongst an estuarine fish assemblage

Temperature (i.e. habitat at any given temperature) is an ecological resource for which organisms compete to maximise growth and other fitness measures, but the temperature (thermal habitat)-resource concept has not been widely applied to the study of estuarine fish. Temperature–abundance relationships for 16 fish and four invertebrate species from the Thames estuary were analysed to test hypotheses regarding temperature resource partitioning. Significant temperature–abundance models were apparent, explaining >65% of the variability in 13 fish species and 50% of variability in three invertebrate species. Fish demonstrated differential responses to temperature across the range. Invertebrates generally preferred warmer conditions than fish. Calculated thermal niche breadths indicated species preferenda spread across the recorded temperature range and some separation along the thermal niche axis within the same functional guild or taxonomic group. Calculated overlap coefficients and resource separation ratios provided some evidence for resource separation and demonstrated that species closely aligned on other niche axes (e.g. physical habitat use, feeding type) were most likely to be separated in terms of their use of thermal habitat resources, suggesting where other niche axes variables are not separating species, division of the temperature resources may be preventing competition between fish species. Few fish species demonstrated significant overlap with potential invertebrate prey, suggesting facultative use of the estuary to exploit optimal thermal habitat rather than food supply. The temporal migration pattern of fish in estuaries is therefore interpreted as a response to resource separation along the temperature axis which limits potential competition between functionally or taxonomically similar species. Thermal resource partitioning in estuaries has temporal rather than spatial dimensions and provides an example of the niche compression/expansion hypothesis.