Assessing the sustainability of cropping systems in single- and multi-site studies. A review of methods     

《European Journal of Agronomy》2016

The multiple new challenges facing agriculture require the development of innovative cropping systems with high environmental, economic and social performances. Many research programmes are currently focusing on the design of such cropping systems. Some include the multicriteria assessment of cropping systems by diverse methods and approaches. Some of these research programmes are supported by experimental or farmers’ networks, generating new opportunities for data analysis and raising new research and methodological questions. In this article, we provide an overview based on a review of 56 articles, comparing the various methods for sustainability assessment in single- and multi-site studies. Articles were classified according to three characteristics: (i) their objectives, (ii) the study design (single- vs. multi-site), (iii) the type of system assessed (fictitious vs. real). Our analysis was structured around four items: (i) the variables used to describe cropping systems and production situations and the use of these variables in the assessment process, (ii) the criteria and associated indicators assessed, (iii) the methods used to explore multiple aspects of the performance of cropping systems, (iv) the use of reference values. We identified key points to be taken into account in multi-site studies. The application of the proposed guidelines to experimental networks should facilitate the identification of high-performance cropping systems and the identification of the drivers of cropping system performance.  相似文献   

加强图书馆联合参考咨询系统的建设,促进文献资源的开发利用     

何苗苗 《农业网络信息》2015,(5)

本文简述了文献传递服务发展的基本过程,概括了联合参考咨询网服务模式与内容,对现阶段UCDRS存在的问题进行分析与探讨,提出了解决问题的方法及优化措施,积极整合各类图书馆信息资源和服务力量,促进公益性联合参考咨询系统的发展。  相似文献   

Evidence-Based Advances in Ferret Medicine     

《Veterinary Clinics of North America: Exotic Animal Practice》2017,20(3):773-803

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Measuring versus estimating net radiation and soil heat flux: Impact on Penman–Monteith reference ET estimates in semiarid regions     

Pedro Gavilán  Joaquín Berengena  Richard G. Allen 《Agricultural Water Management》2007

The standardized ASCE Penman–Monteith and FAO-56 equations were used to estimate reference evapotranspiration (ET₀) using estimated and measured net radiation (R_n) and soil heat flux (G), based on hourly and daily meteorological data. The estimates were evaluated against lysimeter measurements. The results indicate that using measured or estimated values of R_n and G can have significant effect on the accuracy of the ET₀ estimations, especially when calculations were made on an hourly basis. The FAO-56 version performed very well during the irrigation season on a daily basis. The use of measured R_n and G did not improve ET₀ estimation on a daily basis, therefore, the use of estimated R_n and G appears to be dependable when calculations are based on 24-h weather data. When daily ET₀ was calculated from hourly estimations, the results were different depending on the version used. The ASCE version was more accurate, especially when R_n and G were measured. Therefore, measurement of R_n and G may have potential to improve estimation only when daily ET₀ is calculated from hourly estimations. The PM FAO-56 version was always a little less accurate than the ASCE version. For hourly calculations, using a constant surface resistance (as in FAO-56 version), the PM method underpredicted for high evaporative demand and vice versa. The ASCE version performed better than PM FAO-56 version when R_n and G were measured and estimated. Therefore, ASCE version tended to provide quite accurate values of hourly ET₀, even using estimated values of R_n and G. As conclusion, the methods proposed by FAO-56 for estimating R_n and G tended to produce accurate estimates for daily and hourly ET₀ under semiarid conditions and can be used with some degree of confidence for estimating ET₀. In addition, results suggest that the ASCE standardized equation on an hourly basis improved the accuracy of ET₀ estimation with respect to the FAO-56 version.  相似文献   

文冠果实时荧光定量PCR内参基因的筛选     

王旭  敖妍  刘阳  张宁  郑雅琪  刘金凤  张行杰  张永明 《分子植物育种》2020,(9):2977-2986

为筛选适用于文冠果(Xanthoceras sorbifolium Bunge)性别分化过程研究和不同器官的内参基因,本研究以文冠果性别分化关键期的顶芽和侧芽、根、茎、叶、种仁、雌能花和雄能花为材料,通过实时荧光定量PCR(qRT-PCR)鉴定7个候选内参基因(Actin,UBQ,EF-1α,TUB,eIF-4α,18S rRNA和GAPDH)在各样品中的表达量,并评价7个基因的表达稳定性。结果表明,7个候选内参基因在不同样品中的表达量存在明显差异,各基因在雌能花中的表达均显著高于其他材料,在雄能花中的表达处于较低水平;适用于文冠果性别分化过程的最优内参基因为UBQ和eIF-4α,适用于不同器官的最优内参基因为EF-1α和GAPDH。研究结果将对今后进行文冠果性别分化过程研究和不同器官中的基因表达分析提供参考。  相似文献   

Logging pattern and landscape changes over the last century at the boreal and deciduous forest transition in Eastern Canada   总被引：4，自引：0，他引：4  

Yan Boucher  Dominique Arseneault  Luc Sirois  Louis Blais 《Landscape Ecology》2009,24(2):171-184

Forestry practices associated with the industrial era (since ~1900) have altered the natural disturbance regimes and greatly impacted the world’s forests. We quantified twentieth century logging patterns and regional scale consequences in three sub-boreal forest landscapes of Eastern Canada (117,000, 49,400 and 92,300 ha), comparing forestry maps depicting age and forest cover types for early industrial (1930) and present-day (2000) conditions. Results were similar for the three landscapes, indicating large-scale forest change during the twentieth century. In 1930, previous logging activities had been concentrated in the lowlands and along the main hydrographical network, as compared to a more even distribution over the landscapes in 2000, reflecting a decreasing influence of the environmental constraints on forest harvesting. In 1930, old-aged forests (>100 years) accounted for more than 75% of the unlogged areas of the three landscapes, as compared to less than 15% for the present-day conditions. Logging practices have thus inverted the stand age distribution of the landscapes that are currently dominated by young and regenerating stands. The 1930 forest cover types showed a clear relationship with elevation, with conifers located in the lowlands and mixed and deciduous stands restricted to the upper slopes. Between 1930 and 2000, 58–64% of the conifer areas transformed to mixed and deciduous forests, such that no clear altitudinal relationships remained in 2000. We conclude that twentieth century logging practices have strongly altered the preindustrial vegetation patterns in our study area, to the point that ecosystem-based management strategies should be developed to restore conifer dominance, altitudinal gradients, as well as the irregular structure inspired from old forest stands.  相似文献   

中国粮食主产区参考作物蒸散量演变特征与成因分析   总被引：3，自引：0，他引：3  

杨永刚  崔宁博  胡笑涛  龚道枝 《中国农业气象》2018,39(4):245

在全球变暖的背景下,参考作物蒸散量（reference crop evapotranspiration,ET0）的改变及其空间分布势必对中国粮食主产区农业水资源规划、农业用水管理等产生重要影响。本文将中国粮食主产区划分为温带湿润半湿润地区（I区）、温带干旱半干旱地区（II区）、暖温带半湿润地区（III区）和亚热带湿润地区（IV区）4个子区域,基于粮食主产区265个站点1961-2013年53a气象数据,采用FAO-56 Penman-Monteith公式计算各站点逐日ET0,利用ArcGIS空间插值、Mann-Kendall趋势检验、敏感性分析和贡献率分析等方法,对该区域ET0的时空分布规律及其成因进行分析。结果表明：（1）近53a来,中国粮食主产区年均ET0为878.9mm,整体呈显著下降趋势,速率为0.47mm·a^-1（P＜0.05）,I、II区和IV区年均ET0分别为741.8、1079.8和924.2mm且均有所减小,但变化趋势并不明显,III区年均ET0为940.2mm,呈极显著下降趋势,速率为1.21mm·a^-1（P＜0.01）。（2）全区及I-IV区ET0最敏感气象因子均为相对湿度,其敏感系数分别为-1.060、-1.232、-0.784、-1.114和-1.009。（3）全区及I-III区对ET0变化贡献最大的气象因子为风速,IV区为相对湿度。（4）风速的减小是造成粮食主产区全区及I-III区ET0减小的首要原因,风速减小和日照时数缩短是造成IV区ET0减小的主要原因。  相似文献   

黑龙港流域参考作物蒸散量的时序变化和分形特征   总被引：1，自引：0，他引：1  

李春友  张劲松  孟平  黄辉  高峻 《中国农业气象》2011,32(1):81-88

利用位于黑龙港流域的武强、深泽、饶阳、晋州、献县5站1957-2009年日最高气温、日平均气温、日最低气温、日平均相对湿度、日平均风速、日照时数资料,采用Penman-Monteith算法,计算各站不同时间尺度ET0,采用线性趋势分析法分析其趋势倾向,并应用滑动R/S分析方法研究该流域不同时间尺度ET0时间序列的分形特征。线性趋势分析显示,各站历史上自1957年以来的ET0年总值的气候倾向率在-33.81-10.79mm.10a^-1,即均呈下降趋势,但变化倾向率不同;各月ET0倾向率在-11.27-2.02mm.10a^-1,大多数为负值,其中5、6月份各站的下降趋势最大;春、夏、秋、冬季ET0倾向率为-15.87-1.30mm.10a^-1,且夏季各站之间的差异较大,尤以饶阳站与其他4站间的差异最大。气候要素倾向率的对比分析表明,5站参考作物蒸散量总体下降趋势的基本特征主要是由于风速下降、日照时数减少、日最高最低气温上升造成的;5、6月份下降趋势明显则主要是由于风速下降、日照时数减少、日平均气温上升减缓、相对湿度上升明显造成的;饶阳站与其他4站差异较大的主要原因在于2、3、11、12月风速下降和日照时数减少以及日最高最低气温上升趋势减缓、相对湿度和气压下降明显,以致这些月份的ET0倾向率大于0,形成秋季和冬季ET0倾向率大于0,年尺度ET0年际变化下降趋势不明显。R/S分析结果显示,5站全年和各季ET0时间序列的Hurst指数均大于0.5,相关系数均在0.98以上,分维数均小于1.5,说明各站全年和各季节ET0时间序列变化趋势在未来一段时间内具有持续性,即ET0在未来将呈较明显的下降趋势,这种趋势在除饶阳外的其他站月均有不同程度的表现。  相似文献   

非生物胁迫下青花菜LncRNA内参基因的筛选     

裴徐梨  焦鹏  荆赞革  杞如春  王定康  唐征 《西北农业学报》2023,(4):593-599

长链非编码RNA在植物抵御逆境胁迫中起着重要作用。适宜的内参基因是准确评价其表达水平的基础。本研究利用实时荧光定量PCR技术检测16个青花菜LncRNAs表达水平,并通过geNorm、NormFinder、BestKeerper软件进行表达稳定性分析。结果表明：青花菜的16个LncRNAs在不同逆境胁迫下表达稳定性存在差异。其中在弱光胁迫条件下, XLOC_000400表达最稳定;在低温胁迫条件下 XLOC_030832基因稳定性最好;在干旱和渍水胁迫条件下最稳定表达的内参基因分别是 XLOC_007087和 XLOC_012179;高温和盐胁迫处理下最稳定表达的内参基因均为 XLOC_007980。 XLOC_010342和 XLOC_007980在青花菜不同逆境胁迫下的表达稳定性较好。研究结果可为准确定量青花菜不同逆境胁迫下的LncRNAs提供合适的内参基因。  相似文献   

Process modelling in demand-driven supply chains: A reference model for the fruit industry     

C.N. Verdouw  A.J.M. Beulens  J. Wolfert 《Computers and Electronics in Agriculture》2010,73(2):174-187

The growing importance of health in consumption is expected to result in a significant increase of European fruit demand. However, the current fruit supply does not yet sufficiently meet demand requirements. This urges fruit supply chains to become more demand-driven, that is, able to continuously match supply capabilities to changing demand requirements. Realisation of such dynamic supply chains requires the design of customised supply chain configurations and subsequently the engineering of enabling information systems. Reference process models can be valuable means to support this. Based on a case study in four European countries, this paper presents a reference model for designing business processes in demand-driven fruit supply chains. The model consists of a reference modelling framework and an application of the framework to fruit supply chains. The framework defines process models at different levels of abstraction and includes a method of how they can be composed from a repository of building blocks. The applied model comprises a definition of the model building blocks in fruit supply chains and a set of pre-configure models (templates). Together, they combine fruit-specific knowledge with the reuse of generic knowledge as captured in cross-industry standards. The developed reference model bridges the gap between supply chain design and information systems engineering by providing a consistent set of process models that are on the one hand understandable for business managers and on the other hand serve as a basis for information system implementation.  相似文献