Simulating Soil Water Content,Evapotranspiration, and Yield of Variably Irrigated Grain Sorghum Using AquaCrop

Use of models to simulate crop production has become important in optimizing irrigation management in arid and semiarid regions. However, applicability and performance of these models differ across regions, due to differences in environmental and management factors. The AquaCrop model was used to simulate soil water content (SWC), evapotranspiration (ET), and yield for grain sorghum under different irrigation regimes and dryland conditions at two sites in Central and Southern High Plains. Prediction error (P_e), estimated as the difference between simulated and measured divided by measured, for SWC ranged from ?17% to 4% in fully irrigated, ?3% to ?10% in limited irrigated, and ?16% to 25% in dryland treatments. The P_e within ±4%, ?5%, and ?17% to 24% were attained for seasonal ET under fully irrigated, limited irrigated, and dryland conditions, respectively. P_e values for grain yield were within those previously reported and ranged from ?10% to 12%, ?12% to 7%, and 9% to 17% for fully irrigated, limited irrigated and dryland conditions, respectively. Overall performance of the AquaCrop model showed it could be used as an effective tool for evaluating the impacts of variable crop and irrigation managements on the production of grain sorghum in the study area. Finally, the application of the model in the study area revealed planting date has a significant impact on sorghum yield and irrigation requirements, but the impact of planting density was negligible. Editor's note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

Effects of Desertification Caused by Lithophaga lithophaga (Mollusca) Fishery on Littoral Fish Assemblages along Rocky Coasts of Southeastern Italy

Abstract:  We surveyed shallow, rocky reefs in southwestern Apulia (Mediterranean Sea) to assess the effects on coastal fish assemblages of the date mussel (  Lithophaga lithophaga ) fishery, an illegal practice that strips the rocky reef bare. We visually sampled fish four times over 15 months at three locations, one affected by date-mussel fishery and two controls. The fish assemblage at the affected location differed significantly from those at the control locations over all sampling times. Herbivorous fishes, sparids, and labrids (genus Symphodus ) contributed most to the differences between the affected location and controls. Lower densities of Symphodus spp. were observed at the affected location, whereas detritivorous fishes were recorded exclusively at control sites. Small serranids and sparids showed temporal trends that differed between the affected location and the control locations. Our results suggest that the date-mussel fishery affects fish assemblages chiefly through reduction of arborescent macroalgae (contributing to habitat complexity and primary production) and emphasize the need for more effective policing against this destructive practice.     

美国州法中的内径流水权及其优先权日问题

美国水资源的所有权属于各州 ,是一种公有的资源。法律上的水权 ,是水的使用权 ,主要包括私人所有的先占权水权、岸边权水权。在美国西部各州的水权系统中 ,有一种水权现在可以在私法框架中协调环境保护目标、各种取水权人的取水需求 ,这两者之间的冲突。这就是现在美国学术界广泛关注的内径流水权。内径流水权可以在私法领域保护水流的天然禀赋 ,并且排除政府以环境法为理由介入水事争端。随着环境主义在美国的破产[1] ,美国西部开始了大规模的水权裁决活动 ,通过水法院或者行政机构确认私有水权的优先权日 ,从而确立水权的优先权序列。这样水权就会真正成为属于分散的个体的、排他性的财产权。优先权日在先的水权将在枯水季节排除他人的取水权或者其他种类的用水权。因此 ,确立内径流水权在这个优先权序列中的地位 ,是环境保护目标在私法体系中 ,而不是在效率低下的各种环境保护法中 ,长久地得到维护的关键。内径流水权优先权日有 (1)判例法认定的日期 ;(2 )法律规定的日期 ;(3)转化生成的日期。在先占原则框架中扩张这种财产权可以更大程度地排除环境法的适用范围。     

溆浦县枣业发展的SWOT分析及对策探讨

围绕溆浦县枣业发展的现状,运用SWOT分析方法指出该县枣业发展的优势、劣势、机会和威胁,并针对该县枣业发展的问题提出了对策。     

Fitness costs of an immune response in the house martin (<Emphasis Type="Italic">Delichon urbica</Emphasis>)

Immune responses constitute a major way for hosts to defend themselves against parasites. Because hosts do not habitually produce strong responses all the time, immune responses might be costly to produce or maintain. We tested experimentally if the production of a response to a challenge with a novel antigen resulted in a cost in terms of fitness using the highly colonial house martin Delichon urbica as a model system. We injected adult breeding birds during laying of the first clutch with either Newcastle disease virus (NDV) or a control injection, and the clutch was subsequently removed to induce relaying. NDV stimulates the non-specific immune system, causing production of antibodies during a period of more than 2 weeks. Accordingly, we found an increase in leukocyte counts in experimental birds compared to controls. Experimental treatment reduced the frequency of re-laying, caused a delay in timing of relaying and a reduction in brood size. Quality of nestlings in terms of body size, body mass and T-cell-mediated immune response did not differ significantly between treatments. Overall, seasonal reproductive success differed significantly between treatments, showing that the production of an immune response by adult birds is costly in terms of future fecundity.     

气候变化与自然灾害

气候变化与自然灾害是当今科学研究的两大热点，两者之间在一定程度上具有相关性，但目前要确切地定量计算气候变化对自然灾害的强度和出现频率的影响还很困难。本文在分析气候变化与自然灾害关系的基础上，研究了气候变化对我国自然灾害的影响。研究结果显示：１．在千年尺度上，长江流域的大旱和气候变冷成正相关，而长江流域的大涝以及黄河流域的大旱和大涝与气候冷暖过渡期成正相关；２．在百年尽度上，近１０４２年来，共出现２８１次全国性大旱和大涝，平均每百年出现２７次，在地域分布上以南涝北旱为主；３．就百年至千年尺度的气候变化对自然灾害的影响而言，气候冷冷组合期（１３０１～１９００）易发生全国性大涝，而冷暖组合期（９５０～１３００年，１９０１～１９９１年）易发生全国性大旱。总的来说，冷冷组合期的大旱大涝发生频率明显大于暖期，但不同地区有差异；４．在其它影响方面，台风、地震与海啸灾害在冷暖组合期（２０世纪）均有比冷冷组合期（１４和１９世纪）多的趋势。因此，气候变暖将使防灾任务更加艰巨。     

地铁工程安全设计(DFS)知识库构建

针对目前地铁施工和运行过程中安全事故频发的现象,运用安全设计(DFS)概念,提出在地铁设计中应考虑施工和运行安全,构建DFS知识库,以提高设计人员的DFS能力。分析DFS知识库应具备的功能,提出通过知识的搜集、分析、存储和查询4大模块来实现相应的功能;依据模块的功能,详细设计DFS知识库的逻辑结构、系统结构和存储结构;4大模块与DFS不同的结构相结合,构成地铁工程DFS知识库系统。以乘客坠落站台事故为例,进行实证分析。研究结果表明,该案例的逻辑层次为"车站工程子知识库-车站站台子库-客运类事故";合理有效的知识库可根据标准化案例描述识别出危险源,并可运用知识管理的相关方法自动提取针对危险源的设计规范及设计建议。     

黄淮海地区干热风灾害致灾因子时空特征分析

黄淮海地区是我国冬小麦主产区,也是干热风灾害危害最重、影响最广的地区,本研究利用黄淮海冬麦主产区81个站点1961-2017年的逐日气象数据和冬小麦生育期资料,分析了该地区小麦成熟期和干热风致灾因子的时空变化特征。在81个测站中,有23个成熟期提前趋势显著或极显著,但大部地区成熟期变化趋势不显著,有63%的站点未通过显著性检验。对干热风致灾因子达标日数和相似系数的分析表明,达到干热风灾害阈值的概率依次为14:00风速>14:00相对湿度>日最高气温,最高气温是形成干热风的主要限制因素,轻干热风的发生最高气温和相对湿度起主要作用,重干热风则是高温胁迫起决定作用,低湿条件使胁迫加重,风速只起辅助作用。揭示了该地区干热风危害总体减轻的气象条件基础,即干热风3要素表现为最高气温略降、14:00相对湿度略增、14:00风速明显减小的特征,3要素均向有利于减轻干热风发生的方向变化,对于冬小麦籽粒灌浆和产量形成是有利的。但灌浆成熟期内最低气温的显著升高,意味着气温日较差减小、小麦夜间呼吸消耗增大,对其干物质积累和产量形成带来潜在不利影响。     

Supply and demand: causes and consequences of assortative mating in common terns <Emphasis Type="Italic">Sterna hirundo</Emphasis>

Although assortative mating is widespread among long-lived monogamous birds, the underlying mechanisms still remain unclear in many species. In this study, we analysed assortative mating by age and body mass in the common tern Sterna hirundo with special regard to mate choice decisions of newly paired birds. To assess whether assortative mating by age is an active decision involving either homotypic or directional preferences or rather a passive process due to restricted availability of potential mates, we analysed the influence of age-dependent arrival date and cohort size. Furthermore, we looked for direct benefits in terms of reproductive success. Common terns mated assortatively by age and arrival date but not by body mass at arrival. Assortative mating by age was age dependent and was detected mainly in younger birds, whereas birds older than 8 years rather re-paired with younger ones. The availability of same-aged mates was restricted by cohort size and arrival date. We found no general evidence for better reproductive performance of same-aged pairs. Instead, relative reproductive success was related to own age and the relative age of mate: It should be advantageous for any bird to acquire an old mate; hence, assortative mating by age seems to be beneficial only for old terns but not for young ones. Age-assortative mating in common terns occurred by both passive and active processes, which are not mutually exclusive. Our results do not indicate a homotypic but a directional preference and support the theory that high-quality (older/experienced) individuals tend to mate assortatively if same-aged mates are available, which leaves low-quality (young/inexperienced) individuals to mate among themselves.     

川西北高原畜牧业界限温度日期及资源的变化特征

利用川西高原31个气象观测站1961~2012年的观测资料,采用线性趋势法、Mann-Kendall突变检测法和Morlet小波分析方法,详细分析了川西北高原畜牧业界限温度0℃初日、5℃终日及0℃初日至5℃终日之间畜牧气候资源的变化特征。结果表明:(1)川西北高原稳定通过0℃初日及5℃终日在区域上有很大差异,主要受海拔高度、纬度的影响。(2)畜牧气候资源的年际变化总体呈增加趋势,但区域变化不均;(3)各要素年代际变化不同,积温在各个年代都比前一年代增加,而日照时数则呈现出一增两减一增的趋势,降水量的年代际变化型式与日照相反,呈现一减两增一减的趋势;(4)各因素突变特征明显,突变的时间主要出现在20世纪80年代,不同因素的突变类型不同;(5)畜牧业气候资源存在明显的周期性变化,各要素变化周期长短不一致,尤其是降水量以4a左右的短周期振荡为主。