查看更多>>摘要：The construction of dams and weirs has fragmented many rivers and streams globally, and this is a major threat to biodiversity. The most common method used to reduce these impacts is to construct fishways. Published examples show that while fishways can be effective, their performance can also be highly variable. Given this variability, it is critical that transparent targets are set and criteria are developed to assess fishway performance. Often though, this is not done, leading to uncertainty about what constitutes acceptable fishway performance. We present a conceptual framework that illustrates how fishway performance standards sit within a wider process involving objective setting, fishway design, and assessment, and then outline the key principles in the development of fishway performance standards. We highlight the importance of setting clear ecological objectives based on a 'guiding image' (the desired characteristics of the fish assemblage above and below a barrier), and fish passage objectives (i.e. required proportion of the fish assemblages, either individual species or life stages, that needs to be passed without delay and over an expected range of flows). We describe the biological and hydraulic characteristics that need to be considered in performance standards, and highlight the relevance of these characteristics to fish attraction, passage and exit. We use four case studies from diverse riverine systems to provide examples of how performance standards have been set and progress towards their assessment. We conclude by highlighting the potential benefits and risk of using performance standards and identifying areas of uncertainty for future research.
查看更多>>摘要：Open and unreclaimed quarries often host species-rich plant and animal communities. However, the specific factors that determine biodiversity in such anthropogenic habitats are largely unknown. This applies in particular to diverse groups of insects. We therefore studied bee assemblages of 16 limestone quarries, eight active and eight abandoned ones, in a Central European landscape with a long history of quarrying. We analysed the influence of macroclimate, landscape quality and habitat quality on overall species richness as well as on the number of threatened and oligolectic species. Our study revealed strong differences in habitat quality and composition of bee assemblages between active and abandoned quarries. Active quarries were larger, had more different pollen sources and a higher cover of early but a lower cover of later successional stages than abandoned quarries. As a result, species richness of bees was higher in active compared to abandoned quarries. Additionally, active quarries were characterized by a unique bee assemblage consisting of several indicator species. Availability of pollen sources and nesting habitats predicted bee species richness in the quarries. Overall, habitat quality and composition of bee assemblages were strongly dependent on quarry management. Active mining continuously created early-successional stages rich in pollen sources and sunlit nesting habitats, favouring species richness of bees in general and of threatened and oligolectic species in particular. Successional speed is generally low in quarries. Nevertheless, in abandoned quarries, later successional stages increasingly dominated due to ongoing succession and, hence, habitat quality and species richness of bees decreased. Considering this, we propose to expand existing quarries rather than build new ones. From a conservation point of view, this approach has several advantages: (i) existing quarries are often already refuges for colonies of rare species; (ii) many species of conservation concern have a low mobility and are therefore unable to occupy remote habitats and (iii) in the impoverished modern-day landscapes, source population that may colonize new quarries are often lacking.
Hernan Ricardo HadadMaria De Las Mercedes MufarregeGisela Alfonsina Di Luca
9页
查看更多>>摘要：The pollution of natural water bodies and peri-urban wetlands is frequent in the Middle Parana River (Argentina). This work evaluates the potential use of different rooted macrophytes for metal phytoremediation in peri-urban wetlands. Macrophytes, water and sediment were collected in the study sites. Cr, Ni, Zn, Pb, total phosphorus (TP) and total Kjeldahl nitrogen (TKN) were determined in water, sediment, and different plant tissues. Industrial Park and RECU (water dump) showed the highest Cr concentrations. The highest Ni water concentration was observed in Rincon. Industrial Park showed the highest Zn water concentration. The highest Pb water concentration was observed in Industrial Park followed by Rincon. The highest Cr and Zn concentrations in sediment were registered in Industrial Park and Leyes (lake). The sites that showed the highest Ni concentrations in sediment were Industrial Park, RECU (water dump), and Leyes (lake). The high TP concentration measured in the sediment of RECU (water dump) was quite remarkable. Regarding plant tissues, the roots of Pontederia rotundifolia (Leyes, lake), showed the highest Pb concentration. Typha domingensis showed the highest concentrations of Cr, Ni and Zn, in agreement with the highest concentration in sediment. Plants presenting high biomass, such as T. domingensis, are needed to obtain an efficient metal removal from water in peri-urban wetlands. Studies focused on different rooted species will extend the knowledge about metal phytoremediation, management of peri-urban wetlands that receive pollution, and the use of treatment wetlands as nature-based solutions.
Gemma A. CliftonKatharine A. DaffornMelanie J. Bishop
16页
查看更多>>摘要：Artificial structures such as seawalls increasingly dominate marine urban environments. As compared to natural rocky shore habitats, seawalls are usually flat, featureless, vertical surfaces that support reduced biodiversity. One approach to increase their biodiversity is to add topographic complexity ('complexity') that increases microhabitat diversity and surface area. Initial investigations of the effects of complexity on the biodiversity of marine built structures found positive relationships, but more recently spatially variable effects have been found at a biogeographical scale. The present study tested whether at the scale of sites within an estuary (in this case Sydney Harbour), effects of complexity also spatially vary, and whether pollution and estuarine gradients are good predictors of this variation. Comparisons of intertidal communities colonising flat and complex (creviced / ridged) tiles, affixed to seawalls confirmed that effects of complexity were spatially variable at the site-scale, ranging from neutral to highly positive. Proximity to stormdrains, a point source of contaminants including metals, was a poor predictor of complexity effects, but effects were generally greater in the outer harbour, where biodiversity was overall greater, than the inner harbour. These results suggest that eco-engineering interventions based on complexity will not have universally positive effects and instead vary between sites separated by as little as hundreds of meters. Knowledge of spatial variation in physico-chemical conditions and the size and composition of the species pool of available colonists may assist in predicting when and where adding complexity to marine built structures will be of ecological benefit.
查看更多>>摘要：Wildfires are a major disturbance in forest ecosystems around the world and may lead to changes in vegetation succession trajectories. This study examined the impact of time since wildfires on the successional gradients of the degraded Zagros semi-arid oak forest in Iran. Here, we investigated the role of soil seed bank in postfire understory vegetation successional trajectories after wildfires and how time-since-fire influenced plant recovery of this disturbed site. Three adjacent high severity burned areas with different fire histories and the same physiographic conditions were considered. In sampling, we surveyed both aboveground understory vegetation and soil seed bank in all the 96 plots taken along the transects of each area. Soil samples were also collected from each plot and physicochemical properties were analysed in the laboratory. Species composition in the seed bank showed divergent successional trajectories compared to the aboveground vegetation after wildfire. The diversity of soil seed banks followed a gradual decrease, while aboveground understory plants revealed an increasing trend of diversity over time. In addition, the physical and chemical composition of soils was significantly altered by fire. This study presents important insights into soil seed bank dynamics compared to the corresponding aboveground vegetation during postfire succession. The observed changes in diversity and vegetation composition after wildfire can give important insights to management strategies involving prescribed fire in the restoration efforts of highly disturbed semiarid oak forest.
NSTL