Assessment of chemical and physical treatments to selectively kill non-indigenous freshwater zooplankton species     

Louis A. Tremblay  Olivier Champeau  Patrick L. Cahill  Steve Pullan  Natasha Grainger  Ian C. Duggan 《新西兰海洋与淡水研究杂志》2019,53(1):97-112

Non-indigenous zooplankton species pose a biosecurity threat to New Zealand’s freshwater native taxa. Nine species are known to have established in New Zealand lakes to date. The spread of some zooplankton taxa is linked to the translocation of farmed fish, principally grass carp (Ctenopharyngodon idella), and recreational vessel movements. The aims of this study were to assess the effectiveness of a range of chemical and physical treatments for transport water and associated equipment to kill freshwater cladoceran, copepod, and rotifer zooplankton species, and their risk to non-target fish. Sodium chloride was the most effective and applicable chemical treatment tested at length in the cladoceran and, combined with physical treatment via mechanical filtration of water or hot water immersion of equipment (to also manage the risk of diapausing eggs), represents an effective option for the control of non-indigenous zooplankton, with limited impact on stenohaline fish.  相似文献   

Rainfall variability and hydrological and erosive response of an olive tree microcatchment under no‐tillage with a spontaneous grass cover in Spain     

E. V. Taguas  A. Peña  J. L. Ayuso  R. Pérez  Y. Yuan  J. V. Giráldez 《地球表面变化过程与地形》2010,35(7):750-760

Most studies on runoff and soil loss from olive orchards were performed on plots, despite the fact that measurements that examine a range of erosive processes on different scales are essential to evaluate the suitability of the use and soil management of this type of land. The main environmental limitations of much of the land used for olive orchards in the Mediterranean are the steep slopes and the shallow soil depth – and this was the case in the study area. Soil erosion and runoff over two hydrological years (2005–2006 and 2006–2007) were monitored in an olive orchard microcatchment of 6·1 ha under no‐tillage with spontaneous grass in order to evaluate its hydrological and erosive behaviour. Moreover, soil parameters such as organic matter (%OM), bulk density (BD) and hydraulic saturated conductivity (Ks) were also examined in the microcatchment to describe management effects on hydrological balance and on erosive processes. In the study period, the results showed runoff coefficients of 6·0% in the first year and 0·9% in the second. The differences respond to the impact of two or three yearly maximum events which were decisive in the annual balances. On the event scale, although maximum rainfall intensity values had a big influence on peak flows and runoff, its importance on mean sediment concentrations and sediment discharges was difficult to interpret due to the likely control of grass cover on volume runoff and on soil protection. In the case of annual soil erosion, they were measured as 1·0 Mg ha^?1 yr^?1 and 0·3 Mg ha^?1 yr^?1. Both are lower than the tolerance values evaluated in Andalusia (Spain). These results support the implementation of no‐tillage with spontaneous grass cover for sloping land, although the reduced infiltration conditions determined by Ks in the first horizon suggest grass should be allowed to grow not only in spring but also in autumn. In addition, specific measurements to control gullies, which have formed in the terraced area in the catchment, should be included since it is expected that they could be the main sources of sediments. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

四川省林草火险等级评价   总被引：1，自引：0，他引：1  

杨存建  冯凉  杨洪忠  程熙 《地理研究》2010,29(6):980-988

把四川建设成为长江上游生态屏障是四川省的一项重大战略决策。森林和草地资源防火是生态屏障和生态安全保障体系建设的重要内容。林草火险等级的评价对森林和草地资源的防火具有重要的意义。本文利用遥感、GIS和层次分析法对四川省林草火险等级进行了评价。研究表明,就全省而言,火险等级为5级的占0.8%,为4级的占20.2%,为3级的占47.2%;极高火险区主要出现在甘孜州、凉山州、阿坝州、攀枝花市和雅安市,其所占面积百分比分别为49.2%、24.7%、15.7%、3.5%和3.4%;高火险区主要出现在甘孜州、凉山州和阿坝州,其所占面积百分比共达到了72.1%。建议将甘孜州、凉山州、阿坝州、攀枝花以及雅安市作为四川省林草防火的重点区域,在防火的人、财、物上给予优先考虑。  相似文献   

Characteristics of freshly deposited sand and finer sediments along an island-braided, gravel-bed river: The roles of water, wind and trees     

Angela M. Gurnell  Trevor D. Blackall  Geoffrey E. Petts 《Geomorphology》2008,99(1-4):254-269

Over the past two decades there has been a growing interest in the geomorphological mosaic along large floodplain rivers where channel dynamics are seen to drive habitat-patch creation and turnover and to contribute to high biological diversity. This has required a new perspective on fluvial geomorphology that focuses on biological scales of space and time. This study examines the spatial pattern of surface fine sediment accumulations along a reach of a large gravel-bed river, the Tagliamento River in NE Italy; an area with a moist Mediterranean climate and seasonal flow regime. The study investigates changes in sediment characteristics during the summer low-flow period between April and September. Focussing on five areas representing a gradient from open, bar-braided to wooded island-braided morphologies, the paper demonstrates the importance of riparian vegetation and aeolian–fluvial interactions.Significant contrasts in particle size distributions and organic content of freshly deposited sand and finer sediments were found between sampling areas, geomorphological settings, and sampling dates. In particular, wooded floodplain and established islands supported consistently finer sediment deposits than both open bar surfaces and the lee of pioneer islands, and in September significantly finer sediments were also found in deposits located in the lee of pioneer islands than on open bar surfaces. Overall, the September samples had a greater variability in particle size characteristics than those obtained from the same sites in April, with a general coarsening of the D₅ (φ) (i.e., the coarse tail of the particle size distribution). Also in September, crusts of fine sediment (30 μm < D₅₀ < 64 μm) had formed on the surface of some of the open bar and pioneer island deposits within the more open sampling areas along the study reach. These crusts possessed similar particle size characteristics to aeolian crusts found in more arid environments. They were significantly finer than April samples and September subcrust samples obtained from the same sites and had similar particle size characteristics to some samples taken from wooded floodplain, established island surfaces and the lee of pioneer islands that were not crusted.Local climatological and river level data confirm significant wind and rainfall events during a period of consistently low river levels between the April and September sampling periods. These support deflation, deposition and rain wash of finer sediment during the summer, with windblown sediments being deposited on bar surfaces and in the lee of pioneer islands where wood and young trees provide foci for accelerated sedimentation and island growth as well as on marginal floodplains and established islands. We conclude that along braided rivers in moist settings but with a distinct dry season, aeolian reworking of sediment deposits may have a more important role in driving habitat dynamics than previously considered.  相似文献   

Removal of Lead and Chromium from Synthetic Wastewater Using Vetiveria zizanioides          下载免费PDF全文

Veralika Singh  Lokendra Thakur  Prasenjit Mondal 《洁净——土壤、空气、水》2015,43(4):538-543

  相似文献   

草原干旱对天然牧草生长发育及产量形成的影响   总被引：9，自引：0，他引：9       下载免费PDF全文

王英舜  杨文义  贺俊杰  张银锁 《气象》2001,27(2):12-15

天然牧草是放牧畜牧业的主要物质基础，其生长动态和产量形成受气象条件的影响和制约，特别是水分条件在很大程度上决定着植物的地理分布和生物生产力水平。根据降水量及土壤水分条件与天然牧草生长动态及产量的关系，建立了天然牧草生长高度动态模式和草原初级气候生产力模式，以便为进一步研究草原干旱的气候指标提供理论依据。  相似文献   

天山北坡冬草场牧草产量预报模式   总被引：1，自引：0，他引：1  

黄敬锋 《南京气象学院学报》1991,14(4):559-565

  相似文献   

Optimal season for discriminating C3 and C4 grass functional types using multi-date Sentinel 2 data     

Cletah Shoko  Onisimo Mutanga  Timothy Dube 《地理信息系统科学与遥感》2020,57(1):127-139

ABSTRACT

The ability of remote sensing systems to optimally discriminate and map C3 and C4 grass species varies over time, due to environmental changes, which influence their phenological, physiological and morphological characteristics. In this regard, the discrimination of C3 and C4 grasses is insufficient when using a single image acquired at a specific period. In this study, multi-date Sentinel 2A MultiSpectral Instrument (MSI) data were explored to determine the optimal period for classifying and mapping Festuca costata, C3 and Themeda Triandra, C4 grasses in the montane grasslands of South Africa. The study further assessed how seasonal variations in species classification can be explained by climatic variability (rainfall and temperature). Results showed that image acquisition dates influence the discrimination accuracy, spatial representation of the two grass species, as well as the performance of spectral bands. The winter period also presents a better temporal window for discriminating C3 and C4 target grass species, with higher overall classification accuracies (between 91.8% and 95.3%), than summer (between 81.4% and 90.3%). Lower omission (between 2.8% and 11.6%) and commission (between 2.5% and 14.2%) errors were also observed when discriminating using winter images, as compared to those acquired in summer. Summer images showed large grass species areal coverage (e.g. in November and March, C3 and C4 covered ±25%), whereas in winter (mainly August), a notable decrease was observed. Overall, findings of the study have demonstrated the relevance of multi-date Sentinel data in discriminating C3 and C4 grass species. There is, however, a need to explore the classification ability of Sentinel 2 derivatives, especially during early summer and winter fall.  相似文献   

Radio Tomography: A New Experimental Technique   总被引：2，自引：0，他引：2  

S. E. Pryse 《Surveys in Geophysics》2003,24(1):1-38

The technique of radio tomography has developed during the past fifteen years from a theoretical concept to an established experimental method, used for geophysical investigations ofsolar-terrestrial processes. It also has potential in the mapping and modelling of the ionised atmosphere for application to practical radio systems. The method involves measurement of the electron content of the ionosphere along a large number of intersecting satellite-to-receiver ray paths, with tomographic inversion of the data to give a two-dimensional image of the spatial distribution of plasma density in the region of ray-path intersection. The emphasis in this review is on experimental tomographic observations, which have highlighted the capabilities and potential of the technique. Examples are presented from the equatorial sector where the equatorial anomaly is a significant feature, the mid-latitude sector where radio propagation is often influenced by the presence of the main ionisation trough, and the auroral and polar regions where footprints of solar-terrestrial coupling processes are frequently to be seen.  相似文献   

满州里-新巴尔虎区带1∶5万土壤测量方法及找矿应用效果     

程飞  明晋祥  徐桂华  杨继龙 《矿产与地质》2005,(6)

满洲里-新巴尔虎右旗地球化学普查找到一批大、中、小型铜-钼-银-铅-锌矿床,区带化探扫面1∶5万土壤测量对矿床的发现起到至关重要的作用。文章重点论述:①满洲里~新巴尔虎成矿带——干旱、低山丘陵景观区1:5万区带土壤测量工作方法与技术;②区带与典型矿床地球化学异常特征及找矿效果。  相似文献