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61.
Accurate species identification and biogeographic characterisation are fundamental for appropriate management of expanding cephalopod fisheries. This study addresses this topic within the common cuttlefish Sepia officinalis species complex (S. officinalis, S. hierredda and S. vermiculata), with an emphasis on occurrence in African waters. Tissue samples from the currently presumed distributions of S. vermiculata and S. hierredda (from South Africa and Ghana/Angola, respectively) were sequenced for the cytochrome c oxidase subunit I (COI) and the cytochrome b (cytb) genes of the mitochondrial genome and then compared to existing S. officinalis sequences. Three highly divergent and reciprocally monophyletic clades, corresponding to S. officinalis, S. hierredda and S. vermiculata, were resolved, representing the first molecular confirmation of the distinct species status of S. hierredda and S. vermiculata. The sequences also revealed that, contrary to expectations based on presently published information, all samples from southern Angola were S. vermiculata. These results indicate that the range of S. vermiculata extends beyond the currently described northern limit and that S. hierredda and S. vermiculata may be indiscriminately harvested in Angolan waters. Finer-scale patterns within S. vermiculata phylogeography also indicate that the Benguela Current System and/or other environmental factors serve to isolate northern and southern stocks.  相似文献   
62.
Loess soils cover vast areas in the arid and semi-arid regions of northern China. Due to the lack of reliable surface water and ground-water, rainwater harvesting has played a prominent role in farmers’ domestic usage and agricultural irrigation. An economical and valid type of water storage cistern with optimum design of components has been introduced to rural areas in the Loess Plateau. Different collection alternatives showed apparent variations in rainwater quality. By using different catchments, such as mortar roofs and cement-paved courtyards, compacted land or road surfaces, rainwater can be effectively collected for storage in cisterns. This study focused mainly on the quality of rainwater harvested from the different catchment systems and stored for different periods of time. By analysis of the water samples stored in these cisterns, it was evident that rainwater quality could be improved significantly by self-purification during the storage. With emphasis on rainwater quality affected by the different catchment systems, it was found that the measured inorganic compounds in the rainwater harvested from roof-yard catchment systems generally matched the WHO standards for drinking water, while the concentrations of some inorganic compounds in the rainwater collected from land and road surfaces appeared to be higher than the guideline values for drinking water, but generally not beyond the maximum permissible concentrations. However, Fecal Coliform, which is an important bacteriological parameter for the three catchment systems, exceeded the limits of drinking water to a greater extend. Trace amounts of 55 organic pollutants were identified, including aliphatic hydrocarbons, aromatic compounds and phthalate esters, etc. The analytical results indicated that roof-yard catchments that included the “first flush” usually provided safe drinking water with low organic contents, even for rainwater collected immediately after rainfall. In contrast, rainwater harvested from road surfaces had poor quality with respect to the organic constituents, regardless of stored time.  相似文献   
63.
叙利亚阿拉伯共和国地处地中海东岸,北炜32-37.5,东经35.5-42,属于干旱、半干旱地区,是水资源最缺乏的国家之冬季时短多雨,夏季时长干旱.沿海与内陆降雨分布差别很大.按降雨量分,叙利亚可以分为5个农业区.第五个区(Badia盆地)面积占全国的55%,年降雨约150mm,在五个区中最小,被称为叙利亚沙漠.该地区以平原为主,另有一些山脉,土壤特性为含砂粘性土,长年少雨,夏季多风,蒸发率大,相对湿度随着温度的变化而变化.叙利亚沙漠地区的环境适合草地生长,正因为如此, 这里一直是主要的畜牧场所.为了解决该地区雨水不足的问题,政府兴建了很多重大基础工程来改善这里的植被状况.通过雨水收集工程来解决某些地区的饮用水,牲畜用水和灌溉用水.在不同区域建立了 37 座不同规模的大坝、50座小型水库和在平原谷地、梯田地区修建7个拦水坝,还挖掘了很多水井来储存冬季径流,因地制宜种植植物.所有这些工程都是为了最大限度的利用该地区的降水来发展植被、畜牧业和保证沙漠里牧民生活的基本稳定.这篇论文研究了叙利亚沙漠的多种要素(自然因素,气候因素,植被,牲畜,居民……),以及该地区水资源管理方法鹤和关于雨水收集的技术、条件、方法选择及管理等.  相似文献   
64.
Stream temperature was recorded between 2002 and 2005 at four sites in a coastal headwater catchment in British Columbia, Canada. Shallow groundwater temperatures, along with bed temperature profiles at depths of 1 to 30 cm, were recorded at 10‐min intervals in two hydrologically distinct reaches beginning in 2003 or 2004, depending on the site. The lower reach had smaller discharge contributions via lateral inflow from the hillslopes and fewer areas with upwelling (UW) and/or neutral flow across the stream bed compared to the middle reach. Bed temperatures were greater than those of shallow groundwater during summer, with higher temperatures in areas of downwelling (DW) flow compared to areas of neutral and UW flow. A paired‐catchment analysis revealed that partial‐retention forest harvesting in autumn 2004 resulted in higher daily maximum stream and bed temperatures but smaller changes in daily minima. Changes in daily maximum stream temperature, averaged over July and August of the post‐harvest year, ranged from 1.6 to 3 °C at different locations within the cut block. Post‐harvest changes in bed temperature in the lower reach were smaller than the changes in stream temperature, greater at sites with DW flow, and decreased with depth at both UW and DW sites, dropping to about 1 °C at a depth of 30 cm. In the middle reach, changes in daily maximum bed temperature, averaged over July and August, were generally about 1 °C and did not vary significantly with depth. The pre‐harvest regression models for shallow groundwater were not suitable for applying the paired‐catchment analysis to estimate the effects of harvesting. However, shallow groundwater was warmer at the lower reach following harvesting, despite generally cooler weather compared to the pre‐harvest year. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
65.
Forest harvesting activities, if not carefully carried out, can disturb the forest soils and can cause significant suspended solid concentration increases in receiving water. This study examined how harvesting, following forestry guidelines, influenced suspended solid concentrations and loads in the receiving water of a blanket peat salmonid catchment. The study site comprised of two forest coupes of 34‐year‐old conifers drained by a first‐order stream. The upper coupe was not felled and acted as a baseline ‘control’ catchment; the downstream coupe was completely harvested in summer 2005 and served as the ‘experimental’ catchment. Good management practices such as the proper use of brash mats and harvesting only in dry weather were implemented to minimize soil surface disturbance and streambank erosion. Stream flow and suspended solid measurements at an upstream station (US) and a downstream station (DS) in the study stream commenced over a year before felling took place. The suspended solid concentrations, yields and release patterns at US and DS were compared before and after harvesting. These showed that post‐guideline harvesting of upland blanket peat forest did not significantly increase the suspended solid concentrations in the receiving water and the aquatic zone need not be adversely affected by soil releases from sites without a buffer strip. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
66.
Marathwada Agricultural University, Pharbani, has developed about 560 hectares of Wagarwadi watershed in Pharbani district since 1987. Groundwater monitoring on 16 observations wells at weekly intervals commenced in January 1992, and rainfall and pan evaporation has been measured daily at a hydrometeorological station situated in the nearby university campus. Aquifer parameters, namely, transmissivity and specific yield, have been estimated by carrying out a pumping test on a large diameter well. Groundwater recharge resulting from rainfall has been estimated using a water balance model of the soil moisture zone considering soil zone thickness and crops grown. The SCS (Soil Conservation Service) curve number method was used for surface runoff estimation. The groundwater flow model has been constructed using the nested squares, finite difference method. Nested square meshes of sizes 160 m×160 m and 80 m×80 m have been used and the steady-state condition of aquifer system was simulated in the model assuming the June 1992 water level configuration under equilibrium conditions. The model has been calibrated for transient conditions incorporating additional seepage from the water harvesting structures and their contribution to the groundwater regime has been assessed. © 1998 John Wiley & Sons, Ltd.  相似文献   
67.
The most important marine coastal ecosystem in the Chilean coast are kelp forests. This review is based on ecological studies regarding different aspects of subtidal kelp ecosystems along the Chilean coast. It highlights the most interesting findings in (1) biology of subtidal kelp in Chile, with particular reference to (2) habitats formed by kelp, and considered the successful examples and promising results in the (3) kelp as an industrial resource (Biotechnological approach of kelps and aquaculture). The impact caused by (4) El Ni?o-Southern Oscillation is discussed as an important climatic event that could help to forecast the future of the kelp ecosystem. In addition, this literature review outlines the knowledge gaps on subtidal kelp along the Southeast Pacific Coast of Chile, so that research can be strengthened in the future.  相似文献   
68.
对重要干扰过程导致森林植被向大气中的碳排放量进行评估,对于合理评估森林碳汇功能及其在应对全球气候变化中的作用是有重要意义的。本文基于有关森林干扰发生情况的林业统计资料和有关干扰引起生物量C转移过程与比例的假设条件,估算了近20年来采伐、火灾与病虫鼠害三种主要干扰每年从森林植被直接排放到大气中的C量。结果表明,近20年来,中国森林遭受了比较强烈的采伐、火灾与病虫鼠害干扰,并且这三种干扰在进入21世纪后有着比较明显的增加趋势。相应地,在1990-2009年间,采伐、火灾与病虫鼠害的C排放量年均分别为3425.16万tC、161.29万tC、428.80万tC,合计为4015.24万t。三种干扰的总C排放量在1990-1999年间年均为3079.40万t,在2000-2009年间年均为4951.09万t。从不同森林类型分布区的排放来看,中国森林主要干扰的年均C排放量及其年代际变化呈现比较明显的区域特征。干扰对中国森林碳平衡有着重大影响,针对干扰的森林管理可能具有较大的增汇潜力,并且在未来有关森林与陆地生态系统碳收支的模型研究中需考虑主要干扰的影响。  相似文献   
69.
The abandoned Roman/Early Islamic city of Resafa in the Syrian desert steppe was supplied with drinking water by an elaborate floodwater harvesting system. This paper investigates its construction, reliability and chronology. Previous excavations showed that the system consisted of a dam that blocked a wadi adjoining the enclosed city and channeled retained floodwater to large subsurface cisterns. Aerial photos from the early 20th century suggest that additionally embankments were part of the system. Physical evidence of such constructions is largely lacking nowadays.The reliability analysis of the floodwater system is conducted by applying a curve-number-based rainfall-runoff model driven by current satellite rainfall estimates. Flow pattern analysis is used to assess the probable effects of the assumed embankments on flood behavior by applying the hydraulic module of the Caesar-Lisflood model.We show that the system would be reliable under present conditions and probably also functioned when the system was in operation. Furthermore, it is shown that the floodwater harvesting system most likely consisted of a several hundred meter long embankment system.  相似文献   
70.
To investigate the impact of forest harvesting on lake ecosystems, six lakes (four impact, two reference) from central British Columbia, Canada were assessed using cladoceran remains preserved in the lake sediment cores. Two temporal resolutions were analyzed: a decadal scale for the past 70 years, and a high-resolution scale (2 year intervals for ten years before and after harvesting). Three lakes which experienced forestry activity in their watersheds in the early 1960s, and one lake which experienced forestry activityin the mid 1970s, showed subtle but statistically significant changes in cladoceran species composition following forest harvesting (analysis of similarity tests) at the decadal scale, whereas only two of these lakes showed significant changes at the higher resolution. These changes may be due to increased nutrient levels that might be associated with forest harvesting. The two reference lakes, which had not experienced any known large-scale anthropogenic watershed disturbances in the past century, showed no significant shifts in the cladoceran species assemblages at either temporal scale.  相似文献   
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