Runoff initiation in a preserved semiarid Caatinga small watershed,Northeastern Brazil

This study analyses some hydrological driving forces and their interrelation with surface‐flow initiation in a semiarid Caatinga basin (12 km²), Northeastern Brazil. During the analysis period (2005 – 2014), 118 events with precipitation higher than 10 mm were monitored, providing 45 events with runoff, 25 with negligible runoff and 49 without runoff. To verify the dominant processes, 179 on‐site measurements of saturated hydraulic conductivity (Ksat) were conducted. The results showed that annual runoff coefficient lay below 0.5% and discharge at the outlet has only occurred four days per annum on average, providing an insight to the surface‐water scarcity of the Caatinga biome. The most relevant variables to explain runoff initiation were total precipitation and maximum 60‐min rainfall intensity (I₆₀). Runoff always occurred when rainfall surpassed 31 mm, but it never occurred for rainfall below 14 mm or for I₆₀ below 12 mm h^?1. The fact that the duration of the critical intensity is similar to the basin concentration time (65 min) and that the infiltration threshold value approaches the river‐bank saturated hydraulic conductivity support the assumption that Hortonian runoff prevails. However, none of the analysed variables (total or precedent precipitation, soil moisture content, rainfall intensities or rainfall duration) has been able to explain the runoff initiation in all monitored events: the best criteria, e.g. failed to explain 27% of the events. It is possible that surface‐flow initiation in the Caatinga biome is strongly influenced by the root‐system dynamics, which changes macro‐porosity status and, therefore, initial abstraction. Copyright © 2016 John Wiley & Sons, Ltd.     

How does DEM resolution affect microtopographic characteristics,hydrologic connectivity,and modelling of hydrologic processes?

The resolution of a digital elevation model (DEM) is a crucial factor in watershed hydrologic and environmental modelling. DEM resolution can cause significant variability in the representation of surface topography, which further affects quantification of hydrologic connectivity and simulation of hydrologic processes. The objective of this study is to examine the effects of DEM resolution on (1) surface microtopographic characteristics, (2) hydrologic connectivity, and (3) the spatial and temporal variations of hydrologic processes. A puddle‐to‐puddle modelling system was utilized for surface delineation and modelling of the puddle‐to‐puddle overland flow dynamics, surface runoff, infiltration, and unsaturated flow for nine DEM resolution scenarios of a field plot surface. Comparisons of the nine modelling scenarios demonstrated that coarser DEM resolutions tended to eliminate topographic features, reduce surface depression storage, and strengthen hydrologic connectivity and surface runoff. We found that reduction in maximum depression storage and maximum ponding area was as high as 97.56% and 76.36%, respectively, as the DEM grid size increased from 2 to 80 cm. The paired t‐test and fractal analysis demonstrated the existence of a threshold DEM resolution (10 cm for the field plot), within which the DEM‐based hydrologic modelling was effective and acceptable. The effects of DEM resolution were further evaluated for a larger surface in the Prairie Pothole Region subjected to observed rainfall events. It was found that simulations based on coarser resolution DEMs (>10 m) tended to overestimate ponded areas and underestimate runoff discharge peaks. The simulated peak discharge from the Prairie Pothole Region surface reduced by approximately 50% as the DEM resolution changed from 2 to 90 m. Fractal analysis results elucidated scale dependency of hydrologic and topographic processes. In particular, scale analysis highlighted a unique constant–threshold–power relationship between DEM scale and topographic and hydrologic parameters/variables. Not only does this finding allow one to identify threshold DEM but also further develop functional relationships for scaling to achieve valid topographic characterization as well as effective and efficient hydrologic modelling. Copyright © 2016 John Wiley & Sons, Ltd.     

渤中坳陷大型油气系统输导体系及其对油气成藏控制

渤中坳陷东营组沉积期以来快速沉降和强烈断裂活动的地质背景导致其呈现出不同于渤海湾盆地其他地区的油气成藏特征.凹陷周缘凸起带成为油气聚集的主要场所, 输导体系的分布与演化控制了油气运移和成藏.在阐明渤中坳陷大型油气系统烃源岩和油气分布规律的基础上, 综合利用多种资料分析了各类潜在输导通道的发育特征及其空间配置, 识别出断裂主导型、砂体主导型和不整合主导型3类控藏输导体系.凸起边缘继承性的长期断层充当了垂向流体释放和油气运移的主输导通道, 控制了凸起带上新近系储集层中的油气聚集.特别是在构造活跃期, 开启的长期断层成为油气快速垂向运移的首选通道.古近系沙河街组和东营组的连通性砂体与活跃烃源岩直接接触, 不仅是早期油气运移和聚集的主要场所, 也是晚期油气运移和聚集的始发站.因此, 它们不仅控制了古近系圈闭的油气聚集, 同时在很大程度上直接控制了凸起带新近系圈闭的油气供给.不整合T₈是中生代末区域构造变革的产物, 其渗透性因风化作用而得以提高, 充当了深部侧向油气运移的输导通道, 控制了潜山储集层中的油气成藏.3类输导体系对油气成藏的时间、部位、速率和规模等都具有不同程度的影响, 但断裂主导型输导体系的控制作用最为显著.      

利用双重索引快速构建道路网络连通拓扑

路网拓扑关系的生成是进行最优路径规划的基础。本文针对ISO GDF4.0模型对道路连通拓扑的定义,结合最优路径规划对道路网络连通拓扑的要求,提出一种使用R-tree空间索引和B-tree索引双重索引方式快速生成道路连通拓扑的算法。连通拓扑快速构建算法包括新道路生成和网络拓扑提取两部分,新道路生成过程中,首先,自上而下地打断道路形成直线段集并求交点,然后,自下而上地重构直线段集以生成新道路。在打断道路求交点过程中,对道路建立R-tree空间索引,显著提高了几何要素的查找速度。在网络拓扑提取过程中对序列化数据建立B-tree索引,使得其查找速度大大加快。通过对双重索引算法的时间复杂度分析与验证表明,本文提出的拓扑生成算法具有较高的执行效率。     

Modelling wetland connectivity during overbank flooding in a tropical floodplain in north Queensland,Australia

Hydrological connectivity between floodplain wetlands and rivers is one of the principal driving mechanisms for the diversity, productivity and interactions of the major biota in river–floodplain systems. This article describes a method of quantifying flood‐induced overbank connectivity using a hydrodynamic model (MIKE 21) to calculate the timing, the duration and the spatial extent of the connections between several floodplain wetlands and rivers in the Tully–Murray catchment, north Queensland, Australia. Areal photogrammetry and field surveyed stream cross data were used to reproduce floodplain topography and rivers in the model. Laser altimetry (LiDAR)–derived fine resolution elevation data, for the central floodplain, were added to the topography model to improve the resolution of key features including wetlands, flow pathways and natural and artificial flow barriers. The hydrodynamic model was calibrated using a combination of in‐stream and floodplain gauge records. A range of off‐stream wetlands including natural and artificial, small and large were investigated for their connectivity with two main rivers (Tully and Murray) flowing over the floodplain for flood events of 1‐, 20‐ and 50‐year recurrence intervals. The duration of the connection of individual wetlands varied from 1 to 12 days, depending on flood magnitude and location in the floodplain, with some wetlands only connected during large floods. All of the wetlands studied were connected to the Tully River for shorter periods than they were to the Murray River because of the higher bank heights and levees on the Tully River and wetland proximity to the Murray River. Other than hydrology, land relief, riverbank elevation and levee banks along the river were found key factors controlling the degree of connectivity. These variations in wetland connectivity could have important implications for aquatic biota that move between rivers and off‐stream habitats during floods. Copyright © 2011 John Wiley & Sons, Ltd.     

藻类逆境胁迫下信号传导途径的初步研究进展

对目前藻类逆境胁迫下信号传导途径的主要研究进展进行了综述:(1)钙信号系统,藻类通过细胞内Ca2+的变化产生钙信号,Ca2+与钙调素等钙信号受体结合,进而影响钙调素结合蛋白等靶蛋白的活性,从而调控基因表达和生理反应;(2)磷脂酰肌醇信号系统,磷脂酰肌醇在磷脂酶的作用下,水解产生第二信使IP3与DAG,它们可以进一步激活离子通道或蛋白激酶,调节藻类的各种生理反应过程;(3)蛋白质的可逆磷酸化,通过藻类中蛋白质的磷酸化和脱磷酸化,传递信号,并使信号级联放大;(4)蓝藻的二元信号传导系统,蓝藻既具有类似细菌的二元传导系统,又具有真核生物的Ser/Thr或Tyr蛋白质激酶来行使信号传导功能;(5)NO,cAMP等其他信号分子也参与藻类的信号传导途径。     

An empirical study on Chinese city network pattern based on producer services

Globalization and informatization have accelerated city networking process over the world, which makes research on city network a hot topic in the fields of urban geography and economic geography. With Chinese economic structure adjustment and city economic growth, producer services have begun to play an increasingly important role in city-region networking. This paper employs the methodology of world city network to analyze and explain the spatial development characteristics of China’s urban network system based on the data of nationwide producer services enterprise network. The research result indicated that the distribution of producer services network has a positive effect on the development of Chinese city networks. City network connectivity is closely related to the significance of city in producer services development, and the former will gradually decline with the drop of the latter. Accordingly, the 64 cities can be divided into the national central cities, regional central cities, sub-regional central cities and local central cities in accordance with their position and role in the nationwide producer services network. It is concluded that high-grade cities with quality producer services dominate the pattern of Chinese city networks and there emerges three spatial agglomerations of producer services enterprises in Changjiang (Yangtze) River Delta, Zhujiang (Pearl) River Delta and Beijing-Tianjin-Tangshan Economical Region. Moreover, the distribution of different producer services industry varies from city to city, which also affects the characteristics of network development.     

景观连通性理论在城市土地适宜性评价与优化方法中的应用

针对传统的土地适宜性分析方法忽略景观水平生态过程的问题,本文将景观连通性理论应用于土地适宜性评价方法的不同阶段,以达到优化城市生态系统的目标。首先选择影响生物水平流动的主要要素作为评价因子,应用于长沙市望城区滨江片区,确定案例区的土地适宜性评价结果,建构城市土地景观过程阻力评价体系。通过水文连通性分析方法及分布式水文模型确定案例区的潜在雨水生态廊道,将之与土地适宜性评价结果进行加权叠加,根据评估结果,提出案例城市土地适宜性评价的优化方案。结果表明:景观连通性方法适用于传统城市土地适宜性评价方法的改进以及评价结果的优化。     

New Zealand coastal system boundaries, connections and management

Abstract:    Understanding coastal boundaries, connections and drivers of landscape change is integral to effective coastal planning and management. This concept is explored here through case studies representing two very different New Zealand systems: embayed sand beaches in eastern and western open-coast settings; and mixed sand and gravel coast river-mouth lagoons. When framed within a resource and environmental management context these studies indicate that national recognition of the dynamic and interactive nature of coastal environments is a relatively new and amorphous phenomenon in New Zealand and, as such, has been ineffective in driving integrated regional management practices and sustainable coastal outcomes.     

城市供水管网在地震时的连通可靠性分析

考虑地震作用效应和管道抗力的随机特性,建立了埋地管道单元的概率预测模型,评估其在地震时的震害状态。把供水管网系统简化为边权有向网络图,通过Monte Carlo随机模拟过程,近似再现管网中各管段的破坏状态,进而分别结合图论理论方法和模糊关系矩阵法,对管网进行连通可靠性分析。由于Monte Carlo模拟算法是以管网各节点与水源点处于连通状态的近似频率计算来代替精确概率分析,为获得稳定的计算结果,对所用算例进行了5000次模拟。算例分析表明,基于图论方法和模糊关系矩阵法得到的管网连通可靠性结果基本相等。