Impact of environmental factors on bacterial communities in floodplain lakes differed by hydrological connectivity     

《Limnologica》2016

We analysed total bacterial number and mean volume of cells at three sites in each of ten floodplain lakes in the Middle Basin of the Biebrza River, North-Eastern Poland to test bacterioplankton communities change according to the distance to the river. The composition of the bacterial communities was determined by fluorescent in situ hybridization method. Total number of bacteria in the lakes ranged from 4.0 to 7.48 cells × 10⁶ mL⁻¹ with dominance by Actinobacteria, the contribution of which was positively correlated with water level. Old river channels (side-arms) featured Alpha- and Gammaproteobacteria. The community of Betaproteobacteria was limited by concentration of dissolved organic carbon. Archaea, in spite of a minor role (<3.65% of DAPI-4′,6-diamidino-2-phenylindole) in the communities, showed a positive relation to floodplain lake isolation. Multivariate analysis demonstrated that bacterioplankton in riverine lakes was similar to that in rivers, while lakes with limited water exchange showed a similarity to fertile lakes. Water level and nutrients were among the factors determining bacterial community structure.  相似文献   

Perennial frost blisters of the outer Mackenzie Delta,western Arctic coast,Canada          下载免费PDF全文

Peter D. Morse  Christopher R. Burn 《地球表面变化过程与地形》2014,39(2):200-213

Saturated floodplains in Arctic deltas provide conditions favourable for frost mound growth. Little work has been reported from these settings to determine the origin of frost mounds and the controls on their distribution, to assess the longevity of individual mounds, or to quantify variation of mound distribution over time. A case study is presented on low mounds in low‐centred syngenetic ice‐wedge polygons of Big Lake Delta Plain, outer Mackenzie Delta. In 2008 and 2009, 12 mounds were examined by drilling to describe their morphologic variations and to investigate their growth processes. The mounds, containing a core of ice 15 to 58 cm thick, were less than 1 m high and 3 · 7 to 8 · 5 m in diameter; other mounds were over 10 m long. Organic inclusions in the ice, bubble densities, electrical conductivity profiles, and ice‐crystal structure indicated that the mounds were hydrostatic frost blisters. Up to six frost blisters were found within individual polygons due to the relatively small volume of water needed to create each mound. Frost‐blister densities, of greater than 1700 km^–2, increased toward the wet centres of alluvial islands down gentle topographic gradients. The frost blisters were perennial, with individuals remaining identifiable on aerial photographs and satellite images for up to 10 years. Frost blisters collapsed along dilation cracks opened by hydrostatic uplift and by thawing from their sides caused by snow drifting and water ponding. Cyclical growth and decay of the mounds may degrade the visible polygonal network over time. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

How can the uncertainty in the natural inflow regime propagate into the assessment of water resource systems?     

《Advances in water resources》2014

The Canadian Rocky Mountain headwaters support the water resource systems of the Canadian Prairies. Significant variations in natural headwater contributions have been observed due to warming climate. Projecting future natural headwater flows under climate change effects, however, has large uncertainty. First, there are difficulties in climate modeling and downscaling in alpine regions. Second, streamflow modeling in mountainous areas is extremely challenging. There is therefore a need to understand the effects of uncertainty in the natural inflow regime, and in particular how this translates into uncertainty in representing the state and the outflow of water resource systems. Considering the Oldman River basin in Alberta, Canada, we synthesized different inflow regimes based on site/inter-site properties of the historical inflow regime. The water resources system was then conditioned on the synthesized inflow regimes to identify the mechanisms of error propagation from the headwater streamflows to the water allocations. The results show that the response of the water resource system to the uncertainty in the generated inflow regime depends on the system state, flow condition and the component of interest. Generally, the response of the reservoirs to the uncertainty in the estimated inflow regime is more significant in dry years, in particular during low flow conditions. The response at the system outlet is rather different, as the propagation of the headwater uncertainty is more significant during high flow conditions. Also, similar inflow estimates in terms of error and uncertainty may result in different error and uncertainty estimates in the simulated outflows; therefore, lower bias and uncertainty in estimating the regional inflow regime does not necessarily mean lower bias and uncertainty in simulating the streamflow at the outlet of the system. Our results provide improved understanding of uncertainty propagation through complex water resource systems, but also portray the need for better climate and hydrological modeling in the Rocky Mountains for improved water management in the Canadian Prairies, particularly in the face of uncertain climate futures. This will be crucial if the natural headwater inflows decline and/or the system faces drought conditions.  相似文献   

青海省共和-玉树高速公路新建块石路基下的温度状况分析     

冯子亮  盛煜  陈继  曹元兵  吴吉春  李静  胡晓莹  王生廷 《冰川冻土》2014,36(4):969-975

块石路基是多年冻土区应用最为广泛的多年冻土路基形式. 为了研究多年冻土区修筑高速公路后块石路基的效果,选取青海省新建共和-玉树高速公路3个块石路基监测断面的实测资料,对路基修筑初期多年冻土温度状况进行了分析. 结果表明：路基修筑初期路基中心原天然地表下0.5 m处仍表现出季节变化规律,至原多年冻土上限深度处,温度波动幅度急剧减小. 块石路基的保温效果与年平均地温密切相关,年平均地温越低,对冻土的保护效果越显著. 受阴阳坡效应的影响,左路肩/坡脚温度高于右路肩/坡脚. 左右路肩及中心孔下多年冻土上限都得到不同程度的抬升,抬升幅度主要受路基高度影响,与多年冻土年平均地温没有必然关系.  相似文献   

气候变化对黄河上游天然径流量影响分析   总被引：18，自引：3，他引：15  

王金花  康玲玲  余辉  王云璋 《干旱区地理》2005,28(3):288-291

根据黄河上游兰州以上地区1959-2002年历年逐月气温、降水量资料,统计分析了近44年区域气候变化的基本特点,同时通过对各站气温、降水量与兰州站年天然径流量相关系数的计算,选取代表站及典型时段,建立天然径流量计算公式,并计算分析了天然径流量对气候变化的敏感性及气候变化对径流的影响程度。结果表明：(1)年径流量随降水的递增而加大,随气温的升高而减小;(2)径流量对降水变化的响应较其对气温变化的响应更显著;(3)20世纪90年代以来,气候变化对天然年径流量的影响较显著,其影响幅度达13．2％。  相似文献   

Relating a recruitment shift of Patagonian grenadier (Macruronus magellanicus Lönnberg) to large-scale environmental changes off Southern Chile     

LA Cubillos  EJ Niklitschek  S Cahuin 《新西兰海洋与淡水研究杂志》2013,47(2):284-293

The SE Pacific stock of Patagonian grenadier (Macruronus magellanicus) showed evidence of an abrupt reduction in recruitment after 2000. This drop exceeded expectations from changes in the spawning stock biomass (SSB), indicating a change in the stock-recruitment relationship (S-R). We evaluated whether variability in recruitment could be explained by concurrent changes in three environmental indices: sea-surface temperature anomaly (SSTA); southern oscillation index (SOI); and latitudinal position of the west wind drift bifurcation (WWDL). Continuous and discrete effects of these indices were tested as covariates in linear log-log and non-linear Ricker's S-R models. Discrete effects represented regime shifts detected in SSTA (1998), SOI (1998) and WWDL (1995). While SSTA was the only continuous variable found to be significant, the discrete 1998 regime shift supported the most informative model. The best Ricker's model considered a discrete intercept change in the same year: 1998. Although a spurious correlation between SSTA and S-R changes is possible, SSTA may be reflecting major physical or biological changes relevant to M. magellanicus juveniles in the SE Pacific.  相似文献   

Adoption of the arctic search and rescue agreement: A shift of the arctic regime toward a hard law basis?     

Shih-Ming Kao Nathaniel S. Pearre  Jeremy Firestone 《Marine Policy》2012,36(3):832-838

This paper examines the Arctic Search and Rescue Agreement—the first legally-binding instrument negotiated and adopted under the auspices of the Arctic Council—and analyzes its implications for the current Arctic regime. Led by the Arctic Council, the Arctic regime was established in a soft law format. However, the soft law nature and restricted mandates of the Arctic Council have limited its capacity to respond to new issues emerging from climate change, particularly those related to the exploitation of oil and gas reserves, commercial shipping through the region, effects on wildlife, and impacts on indigenous peoples' homelands and culture. The adoption of the Agreement represents a new approach for the Arctic States to respond to these new challenges. At the same time, it does not imply that a legally-binding instrument is necessarily preferable for every issue, and importantly, the new Arctic Agreement does not establish new institutional relationships, suggesting satisfaction among the Arctic States with the existing arrangements. Thus, although the Arctic regime is undoubtedly changing, this change should not be treated today as a shift from soft to hard law. What is more certain is that the Arctic Council will continue to function as a cooperative forum where the Arctic States can address these challenges, and its importance will only increase in coming years.  相似文献   

Assessment of hydrological alterations on wandering beetle assemblages (coleoptera: Carabidae and Tenebrionidae) in coastal wetlands of arid Mediterranean systems   总被引：1，自引：0，他引：1  

M. Teresa Pardo  M.A. Esteve  A. Gimnez  J. Martínez-Fernndez  M.F. Carreo  J. Serrano  J. Miano 《Journal of Arid Environments》2008,72(10):1803-1810

Changes in wandering beetle assemblages (Carabidae and Tenebrionidae) of different habitats situated in coastal wetlands of a Mediterranean arid area (Mar Menor, SE Spain) were analysed in 1984, 1992 and 2003 by pitfall trapping. Over two decades, the increase in irrigated lands at watershed scale led to rising water tables in the Mar Menor wetlands, which affected their beetle communities. These hydrological changes caused an increase in the carabid population, particularly in the sites most affected by flooding, where halobionts and halophiles, which were practically absent in 1984 and 1992, had become dominant by 2003. In contrast, tenebrionid assemblages simplified with time and by 2003 were dominated by one or two generalist species.  相似文献   

Applying local Green's functions to study the influence of the crustal structure on hydrological loading displacements     

《Journal of Geodynamics》2015

The influence of the elastic Earth properties on seasonal or shorter periodic surface deformations due to atmospheric surface pressure and terrestrial water storage variations is usually modeled by applying a local half-space model or an one dimensional spherical Earth model like PREM from which a unique set of elastic load Love numbers, or alternatively, elastic Green's functions are derived. The first model is valid only if load and observer almost coincide, the second model considers only the response of an average Earth structure. However, for surface loads with horizontal scales less than 2500 km², as for instance, for strong localized hydrological signals associated with heavy precipitation events and river floods, the Earth elastic response becomes very sensitive to inhomogeneities in the Earth crustal structure.We derive a set of local Green's functions defined globally on a 1° × 1° grid for the 3-layer crustal structure TEA12. Local Green's functions show standard deviations of ±12% in the vertical and ±21% in the horizontal directions for distances in the range from 0.1° to 0.5°. By means of Green's function scatter plots, we analyze the dependence of the load response to various crustal rocks and layer thicknesses. The application of local Green's functions instead of a mean global Green's function introduces a variability of 0.5–1.0 mm into the hydrological loading displacements, both in vertical and in horizontal directions. Maximum changes due to the local crustal structures are from −25% to +26% in the vertical and −91% to +55% in the horizontal displacements. In addition, the horizontal displacement can change its direction significantly. The lateral deviations in surface deformation due to local crustal elastic properties are found to be much larger than the differences between various commonly used one-dimensional Earth models.  相似文献   

Streamflow regimes of the Yanhe River under climate and land use change,Loess Plateau,China   总被引：1，自引：0，他引：1       下载免费PDF全文

Peng Gao  Guantao Jiang  Yongping Wei  Xingmin Mu  Fei Wang  Guangju Zhao  Wenyi Sun 《水文研究》2015,29(10):2402-2413

Soil and water conservation measures including terracing, afforestation, construction of sediment‐trapping dams, and the ‘Grain for Green Program’ have been extensively implemented in the Yanhe River watershed, of the Loess Plateau, China, over the last six decades, and have resulted in large‐scale land use and land cover changes. This study examined the trends and shifts in streamflow regime over the period of 1953–2010 and relates them to changes in land use and soil and water conservation and to the climatic factors of precipitation and air temperature. The non‐parametric Mann–Kendall test and the Pettitt test were used to identify trends and shifts in streamflow and base flow. A method based on precipitation and potential evaporation was used to evaluate the impacts of climate variability and changes in non‐climate factors changes on annual streamflow. A significant decrease (p = 0.01) in annual streamflow was observed related to a significant change point in 1996, mostly because of significant decreases in streamflow (p = 0.01) in the July to September periods in subsequent years. The annual base flow showed no significant trend from 1953 to 2010 and no change point year, mostly because there were no significant seasonal trends, except for significant decreases (p = 0.05) in the July to September periods. There was no significant trend for precipitation over the studied time period, and no change point was detected. The air temperature showed a significant increasing trend (p < 0.01), and 1986 (p < 0.01) was the change point year. The climate variability, as measured by precipitation and temperature, and non‐climate factors including land use changes and soil and water conservation were estimated to have contributed almost equally to the reduction in annual streamflow. Soil and water conservation practices, including biological measures (e.g. revegetation, planting trees and grass) and engineering measures (such as fish‐scale pits, horizontal trenches, and sediment‐trapping dams) play an important role in reduction of the conversion of rainfall to run‐off. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献