鄱阳湖越冬雁类时空分布特征及热点区域识别

鄱阳湖是东亚—澳大利西亚迁徙路线上重要的水鸟越冬栖息地,雁类是迁徙路线上的优势种群。然而,近年来迁徙路线上的雁类种群数量有所下降,识别越冬地雁类时空分布特征,确定分布热点区域是科学、精准保护的前提。本研究利用2018—2021年越冬期在鄱阳湖区域开展的共58次水鸟调查数据,提取了基于时间序列的白额雁(Anser albifrons)、豆雁(Anserfabalis)、鸿雁(Anser cygnoid)的分布数据,分析了3种雁类在越冬地的种群动态、时间和空间分布动态,评估了鄱阳湖各子湖的重要性,确定了雁类分布热点区域。研究结果表明,3种雁类在越冬地的种群数量表现出一定的年际波动,雁类种群总数量维持在27.9万～44.8万只;不同雁类迁徙的时间节律存在差异,本次地面调查数据显示白额雁、豆雁、鸿雁分别是在10月初至11月初、11月中旬、12月中旬到达鄱阳湖,其中鸿雁到达最晚;高峰期集中在11月底至次年2月初,持续时间约为100天;3种雁类分别在2月中旬、2月底和3月中旬开始迁离鄱阳湖。3种雁类空间分布范围有所差异,豆雁分布范围最广,白额雁分布相对集中,高峰期雁类的分布范围最大,对子湖的利用强...     

Disposition of rainwater under creosotebush

In desert shrubland ecosystems water and nutrients are concentrated beneath shrub canopies in ‘resource islands’. Rain falling on to these islands reaches the ground as either stemflow or throughfall and then either infiltrates into the soil or runs off as overland flow. This study investigates the partitioning of rainwater between stemflow and throughfall in the first instance and between infiltration and runoff in the second. Two series of 40 rainfall simulation experiments were performed on 16 creosotebush shrubs in the Jornada Basin, New Mexico. The first series of experiments was designed to measure the surface runoff and was performed with each shrub in its growth position. The second series was designed to measure stemflow reaching the shrub base and was conducted with the shrub suspended above the ground. The experimental data show that once equilibrium is achieved, 16% of the rainfall intercepted by the canopy or 6·7% of the rain falling inside the shrub area (i.e. the area inside the shrub's circumscribing ellipse) is funnelled to the shrub base as stemflow. This redistribution of the rainfall by stemflow is a function of the ratio of canopy area (i.e. the area covered by the shrub canopy) to collar area (i.e. a circular area centred on the shrub base), with stemflow rate being positively correlated and throughfall rate being negatively correlated with this ratio. The surface runoff rate expressed as a proportion of the rate at which rainwater arrives at a point (i.e. stemflow rate plus throughfall rate) is the runoff coefficient. A multiple regression reveals that 75% of the variance in the runoff coefficient can be explained by three independent variables: the rainfall rate, the ratio of the canopy area to the collar area, and the presence or absence of subcanopy vegetation. Although the last variable is a dummy variable, it accounts for 66·4% of the variance in the runoff coefficient. This suggests that the density and extent of the subcanopy vegetation is the single most important control of the partitioning of rainwater between runoff and infiltration beneath creosotebush. Although these findings pertain to creosotebush, similar findings might be expected for other desert shrubs that generate significant stemflow and have subcanopy vegetation. Copyright © 2003 John Wiley & Sons, Ltd.     

Mental preparation for climate adaptation: The role of cognition and culture in enhancing adaptive capacity of water management in Kiribati

In many Least Developed Countries (LDCs) and Small Island Developing States (SIDS), such as in Kiribati, formal national adaptation programmes are currently being operationalised or are in the pipeline. A key focus is on motivating householders to adapt in anticipation of climate change through pilot community projects. In this paper, we argue that the water sector must pay equal attention to how communities cognitively perceive the process of adaptation if interventions are to be effective. Adopting a cognitive model to gain such insights we conclude that individual's belief in their own abilities to manage water stress play a crucial role in driving intentions to adapt and therefore greater attention needs to be placed on understanding the underling drivers shaping such beliefs.     

海岛界定数量的变维分形特征——以嵊泗县为例

我国多次海岛数量普查因界定标准不一而结果相差巨大,为了满足海洋主管部门对海岛的管理要求,亟需研究合理的方法界定海岛数量。利用高分辨率遥感影像解译嵊泗县海岛2 875个,以分形理论讨论海岛数量与海岛面积、海岛间距的关联。结果表明,嵊泗县50%的海岛面积小于50 m~2或岛间距不足6 m,海岛数量与界定标准间呈分维数先增大后稳定的变维分形特征,分维数在220 m~2和28.5 m之后稳定在1.80和2.25。以200~500 m~2为界区分大小岛,小岛数量和海岛间距也存在变维分形特征,且分维数在间距大于50 m后趋于稳定。故嵊泗海岛最佳界定方法为以220 m~2筛选出计数海岛后再补充间距大于50 m的较小海岛,该方法下界定嵊泗海岛681个。     

Leaf litter decomposition in remote oceanic islands: The role of macroinvertebrates vs. microbial decomposition of native vs. exotic plant species

Freshwater communities on remote oceanic islands can be depauperate due to the influence of biogeographic processes that operate over a range of spatial scales, influencing the colonization of organisms, and events that shape local freshwater assemblages. The consequences of this paucity in organism diversity for the functioning of these ecosystems are, however, not well understood.Here, we examine the relative decomposition rate of leaf litter of native vs. exotic origin by aquatic macroinvertebrates and microbial communities in an isolated and depauperate oceanic environment.Bags containing a standard amount of leaf litter of each of 10 tree species (5 native and 5 non-native species) were deployed on two streams. Two types of bags differing in mesh size were used to allow or prevent the access of leaf litter to macroinvertebrates, respectively. Over a period of 28 days, mass loss of leaf litter was similar in the two bag types suggesting that macroinvertebrates had little influence on the break down of leaf litter in this system. In addition, there was no difference in mass loss of leaf litter of native and exotic origin. Decomposition rates were highly species-specific suggesting that decomposition rates were related to inhibitory substance specific of each leaf species. Our results add to the wider literature by showing that in depauperate and isolated ecosystems, and in contrast to temperate continental ecosystems, decomposition of plant litter by aquatic macroinvertebrates is negligible.     

Large wood retention in river channels: the case of the Fiume Tagliamento,Italy

After more than 300 years of widespread and intensive river management, few examples of complex, unmanaged river systems remain within Europe. An exception is the Fiume Tagliamento, Italy, which retains a riparian woodland margin and unconfined river channel system throughout almost the entire 170 km length of its river corridor. A research programme is underway focusing on a range of related aspects of the hydrology, fluvial geomorphology and ecology of the Tagliamento. This paper contributes to that programme by focusing on large wood retention. The paper adopts a simple force:resistance approach at the scale of the entire river corridor in order to identify reaches of the river with a high wood retention potential. Information on the character of the river corridor is derived from 1:10 000 scale topographic maps. A range of indices measured at 330 transects across the river corridor supports a classification of the geomorphological style of the river which reflects the presence and abundance of properties previously identified in the literature as large wood retention sites. This classification provides a qualitative representation of the ‘resistance’ of the corridor to wood movement and thus its overall wood‐retention potential. The map‐derived indices are also used to extrapolate estimates of the ten year return period flood to each of the 330 transects so that the downstream pattern of unit stream power can be quantified as an index representing ‘force’ in the analysis. Although input of wood is an important factor in many river systems, it is assumed not to be a limiting factor along the Tagliamento, where riparian woodland is abundant. Field observations of large wood storage illustrate that wood retention at eight sites along the river reflects the presence and abundance of the features incorporated in the classification of geomorphological style, including the complexity of the channel network, the availability of exposed gravel areas, and the presence of islands. In general at the time of survey in August 1998, open gravel areas were estimated to store approximately 1 t ha⁻¹ of wood in single‐thread reaches and 6 t ha⁻¹ in multiple‐thread reaches. Established islands were estimated to store an average of 80 t ha⁻¹ of wood. Nevertheless, there was considerable variability between sites, and pioneer islands, which are not represented on maps or readily identified from air photographs because of their small size, were estimated to store an order of magnitude more wood than established islands. Furthermore, the wood storage from this sample of eight sites did not reflect variability in estimated unit stream power. A series of areas for further research are identified, which can be explored using field data, and which will throw more light on the processes of wood retention in this extremely dynamic fluvial environment. Copyright © 2000 John Wiley & Sons, Ltd.     

Medium‐term fluvial island evolution in a disturbed gravel‐bed river (Piave River,Northeastern Italian Alps)

River islands are defined as discrete areas of woodland vegetation surrounded by either water‐filled channels or exposed gravel. They exhibit some stability and are not submerged during bank‐full flows. The aim of the study is to analyze the dynamics of established, building, and pioneer islands in a 30‐km‐long reach of the gravel‐bed Piave River, which has suffered from intense and multiple human impacts. Plan‐form changes of river features since 1960 were analyzed using aerial photographs, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces, and maximum and mean height of their vegetation. The results suggest that established islands lie at a higher elevation than building and pioneer islands, and have a thicker layer of fine sediments deposited on their surface after big floods. After the exceptional flood in 1966 (RI > 200 years) there was a moderate increase in island numbers and extension, followed by a further increase from 1991, due to a succession of flood events in 1993 and 2002 with RI > 10 years, as well as a change in the human management relating to the control of gravel‐mining activities. The narrowing trend (1960–1999) of the morphological plan form certainly enhanced the chance of islands becoming established and this explains the reduction of the active channel, the increase in established islands and reduction of pioneer islands.     

Socioeconomic characteristics and crash injury exposure: A case study in Florida using two-step floating catchment area method

The objective of this study is to investigate the exposure of different population groups to severe injury crash hotspots using an empirical-Gaussian two-step floating catchment area (EG-2SFCA) method based on roadway network distances and a socioeconomic-based weighting approach. This is performed by developing a special form of a crash-to-population ratio index that incorporates the severe crash hotspots relative to the locations of populations they might impact. While identifying these hotspots, four different age groups are considered: 17 and younger, 18 to 21, 22 to 64 and 65 and older. For each age group, severe crash hotspots are identified based on the roadway network and the number of severely injured crash occupants that belong to the specific age group. Using these age-specific crash hotspots and the EG-2SFCA method, communities that were exposed to elevated crash injury risk (crash injury exposure) have been identified. Furthermore, from a residential perspective, a socioeconomic analysis is conducted in order to develop a socioeconomics-based crash injury exposure measure. This measure assesses the exposure of different socioeconomic groups to the risk of being injured. Results demonstrated by applying this measure in the Tampa Bay region, FL show that different population groups are under varying risk of being injured depending on their residential location. The developed approach has the potential to be a social fairness measure able to be applied by agencies, which could enhance the well-being of communities that are subject to elevated injury risk.     

ISLANDS,LOVERS, AND OTHERS

ABSTRACT. Geography, experience, and imagination are all crucial to how we take measure of islands. Prime foci of legend and invention, islands have haunted humanity since the dawn of history. Why are they so intensely loved and loathed, desired and rejected, minutely scrutinized yet often perilously misjudged? On islands we feel alternately landed and adrift, magnified and reduced, fulfilled and voided, at home and in exile. These and other polarities are reviewed here with examples from Caribbean, Atlantic, Mediterranean, antipodean, and imaginary islands fancied by the creator.     

ISLAND MAGIC AND THE MAKING OF A TRANSNATIONAL REGION*

ABSTRACT. How can an artificial island and a bridge‐building project shape the dreams and plans for a transnational region? In this article I examine the making of the öresund region of Denmark and Sweden by analyzing the intertwining of bridge construction and region building, from the early dreams and plans, to the actual construction phase, to the ceremonial opening in 2000, and to the difficult transition into an everyday transportation system. The ways in which the construction was organized and staged came to mirror some important trends of the so‐called new economy and many of its buzzwords. Engineering and imagineering were combined in new ways.