Water use and technical efficiencies in horticultural greenhouses in Tunisia   总被引：1，自引：0，他引：1  

Aymen Frija  Ali Chebil  Stijn Speelman  Jeroen Buysse  Guido Van Huylenbroeck 《Agricultural Water Management》2009,96(11):1509-1516

We measure the technical efficiency of unheated greenhouse farms in Tunisia, and propose a measure for irrigation water use efficiency (IWUE) using an alternative form of the data envelopment analysis (DEA) model. Technical efficiency measures the degree to which (all) farm inputs are used efficiently. IWUE is a measure of the efficiency of irrigation water use when other inputs and output are kept constant. As a second stage, a tobit model is used to identify the degree to which technical efficiency and IWUE correlate with a set of explanatory variables. A comparison of the efficiency scores obtained from constant returns to scale (CRS) and variable returns to scale (VRS) specifications shows that most farmers in our sample are producing at an efficient scale. Under the CRS assumption, the average technical efficiency of the sample was 67.3%. A similar pattern of scores was shown for IWUE; although in this case the average IWUE was even lower (42%). This implies that when all other inputs remain constant, the current output could be produced using, on average, 58% less irrigation water. We conclude that farmers’ technical training in greenhouse management, investments in water saving technologies and the existence of a fertigation technique on farm have a significant and positive effect on their level of IWUE. However, IWUE is significantly and negatively affected by the proportion of total farm land allocated to greenhouses.  相似文献   

Science-policy interface: beyond assessments     

Hulme M  Mahony M  Beck S  Görg C  Hansjürgens B  Hauck J  Nesshöver C  Paulsch A  Vandewalle M  Wittmer H  Böschen S  Bridgewater P  Diaw MC  Fabre P  Figueroa A  Heong KL  Korn H  Leemans R  Lövbrand E  Hamid MN  Monfreda C  Pielke R  Settele J  Winter M  Vadrot AB  van den Hove S  van der Sluijs JP 《Science (New York, N.Y.)》2011,333(6043):697-698

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Relationship between crystallization behavior, microstructure, and macroscopic properties in trans-containing and trans-free filling fats and fillings   总被引：2，自引：0，他引：2  

Vereecken J  Foubert I  Smith KW  Dewettinck K 《Journal of agricultural and food chemistry》2007,55(19):7793-7801

The objective of this study is to investigate the architecture to feature physical functionality of filling fats. This means an investigation of the different structure levels (crystallization, microstructure, macrostructure, etc.) that lead to good technological functionality. The isothermal crystallization behavior of two filling fats (one trans-containing and one trans-free) was examined by differential scanning calorimetry and microscopy. Furthermore, the hardness of the samples was examined after cooling in a water bath at two different temperatures and at three different storage times. The trans-containing filling fat crystallized faster and in smaller crystals as compared to the trans-free filling fat. The crystallization behavior of the trans-free filling fat was more complex, with the formation of different polymorphic forms. The hardness of the fillings was not only governed by the amount of solid fat present in the network but also by the structure of this network. The filling matrix components seem to have a pronounced influence on the microstructure and thus on the macroscopic properties.  相似文献   

Thermal refugia and the survival of species in changing environments: new evidence from a nationally extinct freshwater fish.          下载免费PDF全文

Thomas A. Worthington  Jeroen K. J. Van Houdt  Joshua M. Hull  Paul S. Kemp 《Ecology of Freshwater Fish》2017,26(3):415-423

Variation in global climate during the Quaternary has helped shape current species distributions. The stenohaline fish fauna of the British Isles is generally thought to have colonised eastern England via a landbridge following the last glacial maximum. This theory is investigated using the nationally extinct burbot, Lota lota, as a model species. Samples were collected from 15 museum specimens of known English provenance and analysed for differences in the mitochondrial DNA control region. The DNA analysis produced eight sequences of 270 base pairs, with one sample reaching 420 base pairs in length. Genetic analysis suggests the extinct English population of the burbot was a distinct lineage, differing from those previously described from across the species’ global distribution. Despite this, network analysis suggests that the English lineage is closely related to populations in western Europe, supporting colonisation via a postglacial landbridge. The rate of genetic divergence suggests that the timing of L. lota's colonisation of English rivers was prior to the last glacial maximum. Lota lota appears to have survived the last glacial maximum in refugia within the British Isles. This study adds to the evidence for a British freshwater refugia and furthers our understanding of the colonisation history of British freshwater fishes. These results also provide valuable information for conservation strategies for L. lota indicating the western European clade as most genetically appropriate for potential future reintroductions to English rivers.  相似文献   

Spatio-temporal litterfall dynamics in a 60-year-old mixed deciduous forest     

Jeroen Staelens  Lieven Nachtergale  An De Schrijver  Margot Vanhellemont  Karen Wuyts  Kris Verheyen 《Annals of Forest Science》2011,68(1):89-98

Introduction  

To increase our understanding of litterfall dynamics in mixed-species forests, seasonal and annual variations in litterfall mass and nutrient concentrations were assessed for a 60-year-old spontaneously developed forest dominated by silver birch (Betula pendula Roth), pedunculate oak (Quercus robur L.), and northern red oak (Quercus rubra L.) in Belgium.  相似文献   

Assessing biosecurity practices, movements and densities of poultry sites across Belgium, resulting in different farm risk-groups for infectious disease introduction and spread   总被引：1，自引：0，他引：1  

Van Steenwinkel S  Ribbens S  Ducheyne E  Goossens E  Dewulf J 《Preventive veterinary medicine》2011,98(4):A1-270

The existing diversity within poultry systems affects the potential risk of infectious disease introduction and spread. Population data on the level of biosecurity and between-farm contacts is scarce, despite its importance for identifying possible routes of disease transmission. A study was carried out in Belgium to investigate and differentiate professional and hobby poultry sites based on their biosecurity levels and farm movements. Questionnaire data from a total of 37 professional poultry farms, 19 hatcheries and 286 hobby poultry sites were analyzed using a combination of a linear scoring system, a Categorical principal component analysis (CATPCA) and a Two-Step cluster analysis (TSCA). In general, the level of biosecurity was lower in hobby poultry flocks, mainly due to the poor confinement against the outdoor environment and the poor infrastructural hygiene. Most Belgian professional poultry farms and hatcheries had an acceptable level of adoption of standard biosecurity practices, however less attention was given to the way transportation vehicles and employers were brought onto farms and professional visitors welcomed. Considerable variation in the movements and in the structure of the networks arising from these movements was found. Movement frequencies were higher at professional farms compared to hobby farms. Results showed that multiple category farming systems had the highest total movement frequencies. Monthly frequencies of professional visits often exceeded those of poultry and egg movements. Professional and hobby poultry sites were also connected, but movements of poultry and eggs were found only to occur from professional to hobby sites. However, hobby poultry keepers were personally purchasing the poultry and eggs on the professional poultry sites. Six groups of poultry sites were differentiated, which are interpreted as very low to very high risk groups, based on the potential of infectious disease introduction and spread.  相似文献   

Effect of administration of organic acids in drinking water on faecal shedding of E. coli, performance parameters and health in nursery pigs     

Emily V. De Busser  Jeroen Dewulf  Lieven De Zutter  Freddy Haesebrouck  Jozefien Callens  Tom Meyns  Wout Maes  Dominiek Maes 《Veterinary journal (London, England : 1997)》2011,188(2):184-188

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Shedding patterns of dairy calves experimentally infected with Mycobacterium avium subspecies paratuberculosis     

Rienske AR Mortier  Herman W Barkema  Karin Orsel  Robert Wolf  Jeroen De Buck 《Veterinary research》2014,45(1):71

Although substantial fecal shedding is expected to start years after initial infection with Mycobacterium avium subspecies paratuberculosis (MAP), the potential for shedding by calves and therefore calf-to-calf transmission is underestimated in current Johne’s disease (JD) control programs. Shedding patterns were determined in this study in experimentally infected calves. Fifty calves were challenged at 2 weeks or at 3, 6, 9 or 12 months of age (6 calves served as a control group). In each age group, 5 calves were inoculated with a low and 5 with a high dose of MAP. Fecal culture was performed monthly until necropsy at 17 months of age. Overall, 61% of inoculated calves, representing all age and dose groups, shed MAP in their feces at least once during the follow-up period. Although most calves shed sporadically, 4 calves in the 2-week and 3-month high dose groups shed at every sampling. In general, shedding peaked 2 months after inoculation. Calves inoculated at 2 weeks or 3 months with a high dose of MAP shed more frequently than those inoculated with a low dose. Calves shedding frequently had more culture-positive tissue locations and more severe gross and histological lesions at necropsy. In conclusion, calves inoculated up to 1 year of age shed MAP in their feces shortly after inoculation. Consequently, there is potential for MAP transfer between calves (especially if they are group housed) and therefore, JD control programs should consider young calves as a source of infection.  相似文献   

Habitat structure mediates spatial segregation and therefore coexistence     

Jeroen Boeye  Alexander Kubisch  Dries Bonte 《Landscape Ecology》2014,29(4):593-604

Understanding the mechanisms driving diversity in nature is an important and ongoing challenge in our changing world. To efficiently protect ecosystem diversity it is crucial to explain why and how species coexist. Over the last decades models explaining species coexistence have increased in complexity but usually don’t incorporate a detailed spatial context. However, spatial structure has been shown to affect species coexistence and habitat deterioration is one of the biggest threats to biodiversity. We therefore explore a spatially explicit two-species model and assess the effects of habitat structure on species coexistence using a wide diversity of fractal landscapes. Each species is specialized in a particular habitat type. We find that landscape structure has a major influence on the stability and constitution of a two species system and may be sufficient to explain the coexistence of two species. Well connected and highly structured habitat configurations allow spatial segregation of both species and this decreases local interspecific competition; in our model this is the most important process stabilizing coexistence.  相似文献   

Development of a system for automatic measurements of force and visual stance variables for objective lameness detection in sows: SowSIS     

Liesbet M. Pluym  Dominiek Maes  Jürgen Vangeyte  Koen Mertens  Jeroen Baert  Stephanie Van Weyenberg  Sam Millet  Annelies Van Nuffel 《Biosystems Engineering》2013,116(1):64-74

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