NaCl胁迫对花菖蒲叶片生长及几种生理指标的影响

[目的]探讨花菖蒲的抗盐能力。[方法]以取自江苏省宜兴苗圃的花菖蒲为材料,土壤盐化处理设5个盐度水平(0、0.2%、0.4%、0.6%、0.8%),采用盆栽法,研究不同NaCl胁迫强度条件下花菖蒲的生长及生理生化指标的变化情况。[结果]随着NaCl胁迫强度的增加,花菖蒲的叶片有不同程度的干枯、发黄、失绿、生长势衰退等现象。丙二醛含量、游离脯氨酸含量和SOD活性均随胁迫强度的增大和胁迫时间的延长而整体表现为上升的趋势,叶绿素含量随胁迫强度和胁迫时间的延长呈不断降低的趋势。通过对外观形态的观测以及生理指标的分析,推断出花菖蒲的耐盐阈值是0.4%,存活阈值是0.8%。[结论]该研究为改良土壤、绿化水体、湿地和盐碱地景观的营建提供了科学依据。     

基于阈值分析法的江淮流域汛期极端强降水变化特征分析

利用1951～2004年江淮流域91个测站汛期(5～9月)的逐日降水资料,采用阈值分析方法来确定强降水的阈值,对强降水阈值和日数的空间分布特征进行分析。结果表明,江淮流域中西部地区强降水阈值总体呈南高北低的分布特征,东部地区呈南高-中低-北高的分布特征;54年间江淮流域有4个年际变化突出的区域;强降水日数总体上呈南高北低的趋势,且54年的年际变化不明显。     

Effects of stream map resolution on measures of riparian buffer distribution and nutrient retention potential

Riparian ecosystems are interfaces between aquatic and terrestrial environments recognized for their nutrient interception potential in agricultural landscapes. Stream network maps from a broad range of map resolutions have been employed in watershed studies of riparian areas. However, map resolution may affect important attributes of riparian buffers, such as the connectivity between source lands and small stream channels missing in coarse resolution maps. We sought to understand the influence of changing stream map resolution on measures of the river network, near-stream land cover, and riparian metrics. Our objectives were: (1) to evaluate the influence of stream map resolution on measures of the stream network, the character and extent of near-stream zones, and riparian metrics; (2) to compare patterns of variation among different physiographic provinces; and (3) to explore how predictions of nutrient retention potential might be affected by the resolution of a stream map. We found that using fine resolution stream maps significantly increased our estimates of stream order, drainage density, and the proportion of watershed area occurring near a stream. Increasing stream map resolution reduced the mean distance to source areas as well as mean buffer width and increased the frequency of buffer gaps. Measures of percent land cover within 100 m of streams were less sensitive to stream map resolution. Overall, increasing stream map resolution led to reduced estimates of nutrient retention potential in riparian buffers. In some watersheds, switching from a coarse resolution to a fine resolution stream map completely changed our perception of a stream network from well buffered to largely unbuffered. Because previous, broad-scale analyses of riparian buffers used coarse-resolution stream maps, those studies may have overestimated landscape-level buffer prevalence and effectiveness. We present a case study of three watersheds to demonstrate that interactions among stream map resolution and land cover patterns make a dramatic difference in the perceived ability of riparian buffers to ameliorate effects of agricultural activities across whole watersheds. Moreover, stream map resolution affects inferences about whether retention occurs in streams or riparian zones.     

水果品质检测中的模糊阈值分割方法

为实现利用机器视觉技术进行水果检测分级，对水果检测图像的分割进行了研究。依据模糊集合理论，提出了先验知识引导的自适应模糊阈值分割算法，实验表明该方法应用效果较好。     

Efficient cooling of cities at global scale using urban green space to mitigate urban heat island effects in different climatic regions

In the context of rapid urbanization and global warming, how to use urban green space (UGS) with high-efficiency to mitigate the urban heat islands (UHIs) effect in different climate zones has become an urgent issue. However, few studies have provided specific guidance for urban vegetation planning adapting to different climate zones on a global scale. In this study, a cooling effect framework was employed to analyze the influence of UGS patch characteristics, natural and anthropogenic factors on its cooling effect across different climatic zones. We found that the urban cooling islands (UCI) intensity, extent, and gradient of UGS increased with latitude, with lower cooling effect concentrated in arid zones around 30 °N, while the largest (0.38 ha) and smallest (0.24 ha) threshold value of efficiency (TVoE) were found in the temperate and arid climate zones. The larger the UGS area, the better the cooling effect in all climate zones. Moreover, complex shapes have a greater UCI intensity in tropical and temperate zones than other regions, while the normalized difference vegetation index (NDVI) has a stronger effect in arid zones. In the continental zone, patch characteristics had little effect. The overall explanation rate of natural and anthropogenic factors on the cooling effect of UGS was 53.5 %, among which natural factors were approximately twice that of anthropogenic factors. Notably, natural factors dominated in the tropical and arid zones affecting UCI, and anthropogenic factors dominated in the temperate and continental zones. The findings of this study expand our understanding of the cooling effect of UGS in different climatic zones around the world and provide insights for urban sustainable development.     

Hip dysplasia in Estrela mountain dogs: prevalence and genetic trends 1991-2005

Three hundred and thirteen Estrela mountain dogs were examined for hip dysplasia (HD) using the standard ventrodorsal hip extended view, and graded into five categories (A, B, C, D and E) using the Fédération Cynologique Internationale’s (FCI) scoring system. The Ortolani method was performed to evaluate hip joint laxity. Pedigree information was obtained from the Portuguese Kennel Club and the genetic trend was evaluated by calculating the mean breeding values (BVs) for the last 15 years, using the threshold model.HD was found in 66% of the dogs. There was low-moderate correlation between the results of the Ortolani test and FCI hip scores (r_s = 0.386; P < 0.001). Grades of hip dysplasia were equal in both males and females (P = 0.14) and in the animals’ right and left sides (P = 0.51). The mean BVs for HD were stable in dogs born between 1991 and 2003, and showed an improvement in 2004 and 2005. The data confirm the high prevalence and severity of HD in predisposed breeds that do not have breeding programmes in place. It also confirms an initial favourable change in BVs that is a likely consequence of the voluntary radiographic hip-screening programme.     

Two measures of landscape-graph connectivity: assessment across gradients in area and configuration

Landscape connectivity is critical to species persistence in the face of habitat loss and fragmentation. Graph theory is a well-defined method for quantifying connectivity that has tremendous potential for ecology, but its application has been limited to a small number of conservation scenarios, each with a fixed proportion of habitat. Because it is important to distinguish changes in habitat configuration from changes in habitat area in assessing the potential impacts of fragmentation, we investigated two metrics that measure these different influences on connectivity. The first metric, graph diameter, has been advocated as a useful measure of habitat configuration. We propose a second area-based metric that combines information on the amount of connected habitat and the amount of habitat in the largest patch. We calculated each metric across gradients in habitat area and configuration using multifractal neutral landscapes. The results identify critical connectivity thresholds as a function of the level of fragmentation and a parallel is drawn between the behavior of graph theory metrics and those of percolation theory. The combination of the two metrics provides a means for targeting sites most at risk of suffering low potential connectivity as a result of habitat fragmentation.     

The influence of research scale on bald eagle habitat selection along the lower Hudson River,New York (USA)

As the concepts of landscape ecology have been incorporated into otherdisciplines, the influence of spatial patterns on animal abundance anddistribution has attracted considerable attention. However, there remains asignificant gap in the application of landscape ecology theories and techniquesto wildlife research. By combining landscape ecology techniques withtraditionalwildlife habitat analysis methods, we defined an organism-centeredperspectivefor breeding bald eagles (Haliaeetus leucocephalus) alongthe Hudson River, New York, USA. We intensively monitored four pairs ofbreedingeagles during the 1999 and 2000 breeding seasons, and collected detailedinformation on perch and forage locations. Our analysis focused on threecritical habitat elements: available perch trees, access to foraging areas, andfreedom from human disturbance. We hypothesized that eagle habitat selectionrelative to each of these elementswould vary with the spatial scale of analysis, and that these scalingrelationships would vary among habitat elements. We investigated two elementsofspatial scale: grain and local extent. Grain was defined as the minimum mappingunit; local extent was defined by the size of an analysis window placed aroundeach focal point. For each habitat element, we quantified habitat use over arange of spatial scales. Eagles displayed scale-dependent patterns of habitatuse in relation to all habitat features, including multi-scale andthreshold-like patterns. This information supports the existence ofscale-dependant relationships in wildlife habitat use and allowed for a moreaccurate and biologically relevant evaluation of Hudson River breeding eagle habitat.This revised version was published online in May 2005 with corrections to the Cover Date.     

Genetic study of individual preweaning mortality and birth weight in Large White piglets using threshold-linear models

Individual records from 49,788 Large White piglets were used to evaluate preweaning mortality and its relationship with birth weight (BW). Preweaning mortality included farrowing mortality (TM) was also divided into stillbirth (SB), early (EM), late (LM) and total (ELM) preweaning mortality. Farrowing mortality was also studied as a sow's trait as number of piglets born dead (NBD). Threshold-linear models were used via MCMC. Traits included (1) TM-BW, (2) SB-ELM-BW, (3) SB-EM-LM and (4) NBD-ELM-BW. Model for BW included parity number, litter size, sex, contemporary group (farm-farrowing year-month), litter, and direct and maternal additive genetic effects. For mortality traits, litter effect was of the nursing litter for cross-fostered piglets (4.9%). Models for SB (2, 3) and NBD (4) excluded the effect of sex. In Model 3, BW was fitted as covariable for EM and LM. Estimates of direct and maternal heritability for BW were 0.03–0.06 and 0.14–0.19; and for mortality traits 0.03–0.12 and 0.08–0.12. Direct-maternal correlations were negative for all traits. Genetic correlations between all mortality traits were positive. Results confirmed the importance of BW for the genetic evaluation of piglet mortality. Early mortality is a good candidate for improvement of TM because of larger heritability and high genetic correlations with other mortality traits. It is most efficient to treat SB at sow level and preweaning mortality at the piglet level.