简单、复杂与地理分布模型的选择

地理分布的数学建模是空间分析的基本途径之一,但空间维度建模素为科学研究的难题。由于数学新方法的发展和复杂性研究的兴起,地理空间建模的一些传统困难有望解决。本文通过两类地理分布的对比分析,论述地理建模的关键在于简单分布的特征尺度和复杂分布的标度。地理分布包括空间分布和规模分布,其本质均为概率分布和广义的数学空间分布,而概率分布可以分为简单分布和复杂分布。简单分布具有特征尺度,平均值有效,概率结构清楚;复杂分布没有特征尺度,平均值无效,概率结构不明确。对于简单分布,应该采用有尺度分布函数开展尺度分析;对于复杂分布,理当采用无尺度分布函数开展标度分析。分形几何学、异速生长理论和无尺度网络理论都是复杂系统分析的定量方法,这些方法的综合集成,可望为地理分布建模和地理系统的空间分析提供有效的数理工具。     

红树植物外来种无瓣海桑对乡土种秋茄形态特征与生物量的影响

本文研究红树植物外来种无瓣海桑对乡土种秋茄形态可塑性、生物量积累、生物量分配的影响。实验样地设在福建省漳州市漳浦县"东山湾滨海湿地互花米草防控与生态修复示范基地",共设置4种样地类型,秋茄种植间距为0.25 m×0.25 m(Ⅰ)的秋茄人工纯林、种植间距分别为0.5 m×0.5 m(Ⅱ)、1 m×1 m(Ⅲ)、2 m×2 m(Ⅳ)外来种无瓣海桑与秋茄(种植间距为25 cm×25 cm)人工混交林。结果表明:种植无瓣海桑,导致3种混交林样地秋茄的形态指标(H、D)、生物量(AGB、BGB、TB、R/S)在不同季节均表现出显著或极显著低于秋茄纯林对照样地;随着无瓣海桑种植间距的减小,秋茄形态指标、生物量也会发生显著的减小趋势;秋茄的形态特征、R/S、BGB与AGB之间均表现出极显著的异速生长关系,混交林的异速生长关系指数和决定系数均显著小于秋茄纯林,随着无瓣海桑种植间距的不断减小;BGB与AGB之间的斜率发生显著减小的趋势。说明:种植无瓣海桑在一定程度上导致秋茄明显发生个体发育漂变,并在一定程度上显著抑制秋茄的形态可塑性、生物量的积累、增长速率和分配格局。随着无瓣海桑种植间距的减小,在一定程度上,使秋茄个体发育漂变程度更加明显,对秋茄形态可塑性、生物量的积累、增长速率和分配格局的抑制作用显著加强。研究结果表明种植外来种无瓣海桑对乡土种秋茄具有一定程度的入侵倾向。     

南极菲尔德斯半岛两侧南极帽贝种群结构比较分析

本文对南极乔治王岛菲尔德斯半岛东、西海岸的帽贝种群的个体分布特征进行了研究,样品于2003年2月南半球夏季在菲尔德斯半岛东面的长城湾长城站一侧和企鹅岛西侧潮间带以及半岛西岸地理湾潮间带采集。在上述三个站点作断面随机取样,分别统计了南极帽贝(Na-cella concinna Strebel,1908)密度和个体大小。结果表明,除了半岛两侧帽贝种群密度不同外,半岛东、西两侧帽贝个体大小也存在较大的差异,西海岸地理湾帽贝壳长明显较大,大于企鹅岛帽贝平均壳长1cm以上,其他生长指标也大于东海岸的帽贝。西海岸帽贝个体的腹足面积和壳高的回归直线的斜率均大于东海岸帽贝的对应值。东、西海岸帽贝的腹足与帽贝的壳高存在异速生长状况(allometry),西海岸帽贝异速生长差异高于东海岸的帽贝。分析结果进一步证明,当地低密度帽贝种群与西海岸比较恶劣的自然环境有关,环境差异导致西岸产生大个体帽贝。菲尔德斯东、西海岸环境因子,如风浪、冰块冲击作用以至生物捕食产生的环境压力,不仅作用于种群个体的生长状态,而且也作用于种群结构。     

Predicting forest structural parameters using the image texture derived from WorldView-2 multispectral imagery in a dryland forest,Israel

Estimation of forest structural parameters by field-based data collection methods is both expensive and time consuming. Satellite remote sensing is a low-cost alternative in modeling and mapping structural parameters in large forest areas. The current study investigates the potential of using WordView-2 multispectral satellite imagery for predicting forest structural parameters in a dryland plantation forest in Israel. The relationships between image texture features and the several structural parameters such as Number of Trees (NT), Basal Area (BA), Stem Volume (SV), Clark-Evans Index (CEI), Diameter Differentiation Index (DDI), Contagion Index (CI), Gini Coefficient (GC), and Standard Deviation of Diameters at Breast Heights (SDDBH) were examined using correlation analyses. These variables were obtained from 30 m × 30 m square-shaped plots. The Standard Deviation of Gray Levels (SDGL) as a first order texture feature and the second order texture variables based on Gray Level Co-occurrence Matrix (GLCM) were calculated for the pixels that corresponds to field plots. The results of the correlation analysis indicate that the forest structural parameters are significantly correlated with the image texture features. The highest correlation coefficients were calculated for the relationships between the SDDBH and the contrast of red band (r = 0.75, p < 0.01), the BA and the entropy of blue band (r = 0.73, p < 0.01), and the GC and the contrast of blue band (r = 0.71, p < 0.01). Each forest structural parameter was modeled as a function of texture measures derived from the satellite image using stepwise multi linear regression analyses. The determination coefficient (R²) and root mean square error (RMSE) values of the best fitting models, respectively, are 0.38 and 109.56 ha⁻¹ for the NT; 0.54 and 1.79 m² ha⁻¹ for the BA; 0.42 and 27.18 m³ ha⁻¹ for the SV; 0.23 and 0.16 for the CEI; 0.32 and 0.05 for the DDI; 0.25 and 0.06 for the CI; 0.50 and 0.05 for the GC; and 0.67 and 0.70 for the SDDBH. The leave-one-out cross-validation technique was applied for validation of the best-fitted models (R² > 0.50). In conclusion, cross-validated statistics confirmed that the structural parameters including the BA, SDDBH, and GC can be predicted and mapped with a reasonable accuracy using the texture features extracted from the spectral bands of WorldView-2 image.     

Seasonal, Geographical and Size Differences in Oxygen Consumption, Digestive Gland and Gills in Carcinus maenas (L), a Study of Condition for Ecologists

Abstract. The excited rate of oxygen consumption, and the wet weights of the digestive gland and the gills were studied in relation to overall size. One experiment was made in Roscoff, France, one in Portaferry, N. Ireland, and three in Wicklow, Ireland. Higher levels of oxygen consumption were found in Roscoff together with greater gill weight. Seasonal changes in the level of oxygen consumption in Wicklow may be influenced by the dry wt/wet wt ratio of the gills - probably an index of condition for the crabs as a whole. The power functions for allometric growth were virtually constant for each factor in all five experiments. All levels of factors were reduced in males weighing more than 60 g. Disproportions in the weights of the chelae marked the populations in Roscoff and Portaferry, compared with Wicklow. These suggest a genetic basis for the geographical differences in oxygen consumption and gill weight. The importance of local experiments for local conditions and the possibilities for predicting physiological rates from morphology are discussed.     

多枝柽柳和疏叶骆驼刺幼苗生物量分配及根系分布特征

以塔克拉玛干沙漠南缘荒漠-绿洲过渡带上两种主要建群种植物多枝柽柳(Tamarix ramosissima)和疏叶骆驼刺(Alhagi.sparsifolia SHAP.)的一年生幼苗为研究对象,采用人工壕沟全根挖掘法,研究同一生境条件下两种植物幼苗在生物量分配、根冠比、根系分布特征对极端干旱环境的适应特征.结果表明:(1)两种植物幼苗生物量分配策略明显不同.多枝柽柳幼苗把更多的生物量分配到地上,其根冠比为0.75;而疏叶骆驼刺幼苗把更多的生物量分配到地下,其根冠比为1.73.(2)两种植物幼苗地上/地下生物量属于典型的幂函数异速生长关系,异速生长模型的相关系数都在0.83以上.(3)两种植物幼苗根系分布各异.多枝柽柳幼苗根系多由垂直的主根和水平扩展的侧根组成,根长在垂直剖面上近似"丰"字形分布;骆驼刺幼苗根系在土壤中呈网状分布,根长在垂直剖面上近"古"字形分布.