Diversity and production of Ethiopian dry woodlands explained by climate- and soil-stress gradients   总被引：1，自引：0，他引：1  

Abeje Eshete  Frank Sterck  Frans Bongers 《Forest Ecology and Management》2011,261(9):1499-1509

Dry woodlands cover about 14% of the total African land surface and represent about 25% of the natural vegetation. They are characterized by a seasonal climate, with a dry season of 4-7 months. Large parts of these ecosystems are degrading due to grazing, fire or exploitation by people. We studied species richness and productivity patterns of dry woodlands in Ethiopia. For such ecosystems, classic productivity and diversity hypotheses predict that species richness and productivity increase as the wet season length increases, and decrease when soil conditions create water stress. We inventoried and measured trees in 18 2-ha plots distributed in two sites, one higher altitude site with a shorter wet season than the lower altitude site. We found that the stand volume per hectare was lower in the site with a shorter wet season. Across all 18 plots we observed that stand volume decreased with soil water stress (estimated from texture and depth). This was in line with the prediction. The species richness was lower in the short-wet-season woodlands, but was unaffected by variation in soil conditions. This suggests that climate driven constraints (wet season length) set the limits to species richness, and not soil conditions. As far as we know, this study is one of the first studies that evaluated these productivity and diversity hypotheses for dry African woodlands.  相似文献   

Simple media and conditions for inter-laboratory transport of Campylobacter jejuni isolates     

Omurtag I  Aydin F  Paulsen P  Hilbert F  Smulders FJ 《The Veterinary quarterly》2011,31(2):73-75

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Risk management in primary apicultural production. Part 2: a Hazard Analysis Critical Control Point approach to assuring the safety of unprocessed honey     

Formato G  Zilli R  Condoleo R  Marozzi S  Davis I  Smulders FJ 《The Veterinary quarterly》2011,31(2):87-97

In managing risks associated with the human consumption of honey, all sectors of the production chain must be considered, including the primary production phase. Although the introduction of the Hazard Analysis Critical Control Point (HACCP) system has not been made compulsory for purposes of quality and safety control in farming operations, European legislation makes many references to the key role of primary production in food safety management and the HACCP system has been indicated as the preferred tool to ensure that consumers are provided with safe foods. This article describes a systematic HACCP-based approach to identifying, preventing and controlling food safety hazards occurring in primary apicultural production. This approach serves as a useful tool for beekeepers, food business operators, veterinary advisors, and for Food and Veterinary Official Control Bodies in their planning and conducting of audits and for establishing priorities for the evaluation of training programmes in the apicultural sector.  相似文献   

Cerebral Accumulation of Dietary Derivable Plant Sterols does not Interfere with Memory and Anxiety Related Behavior in Abcg5?/? Mice     

Vanmierlo T  Rutten K  van Vark-van der Zee LC  Friedrichs S  Bloks VW  Blokland A  Ramaekers FC  Sijbrands E  Steinbusch H  Prickaerts J  Kuipers F  Lütjohann D  Mulder M 《Plant foods for human nutrition (Dordrecht, Netherlands)》2011,66(2):149-156

Plant sterols such as sitosterol and campesterol are frequently applied as functional food in the prevention of atherosclerosis. Recently, it became clear that plasma derived plant sterols accumulate in murine brains. We questioned whether plant sterols in the brain are associated with alterations in brain cholesterol homeostasis and subsequently with brain functions. ATP binding cassette (Abc)g5-/- mice, a phytosterolemia model, were compared to Abcg5+/+ mice for serum and brain plant sterol accumulation and behavioral and cognitive performance. Serum and brain plant sterol concentrations were respectively 35-70-fold and 5-12-fold increased in Abcg5-/- mice (P<0.001). Plant sterol accumulation resulted in decreased levels of desmosterol (P<0.01) and 24(S)-hydroxycholesterol (P<0.01) in the hippocampus, the brain region important for learning and memory functions, and increased lanosterol levels (P<0.01) in the cortex. However, Abcg5-/- and Abcg5+/+ displayed no differences in memory functions or in anxiety and mood related behavior. The swimming speed of the Abcg5-/- mice was slightly higher compared to Abcg5+/+ mice (P<0.001). In conclusion, plant sterols in the brains of Abcg5-/- mice did have consequences for brain cholesterol metabolism, but did not lead to an overt phenotype of memory or anxiety related behavior. Thus, our data provide no contra-indication for nutritional intake of plant sterol enriched nutrition.  相似文献   

Restriction fragment length polymorphism inSolanum spp for the construction of a genetic map ofSolanum tuberosum L.: a preliminary study     

John J. M. R. Jacobs  Frans A. Krens  Willem J. Stiekema  Martin van Spanje  Marinus Wagenvoort 《Potato Research》1990,33(2):171-180

Summary When using two restriction enzymes and DNA probes from different sources, high levels of restriction fragment length polymorphism (RFLP) were observed in Southern blot hybridisation experiments, among 6 di(ha)ploid genotypes ofSolanum tuberosum and some closely related species. In 3 F1 sample populations of 14 individuals each, both heterozygosity and segregation of hybridisation patterns were observed. The non-radioactive biotin-dUTP/SA-AP method for DNA detection on Southern blots proved to be satisfactory and reliable.  相似文献   

Prevention strategies for field traffic-induced subsoil compaction: a review: Part 2. Equipment and field practices     

Tim Chamen  Laura Alakukku  Sandra Pires  Claus Sommer  Gordon Spoor  Frans Tijink  Peter Weisskopf 《Soil & Tillage Research》2003,73(1-2):161-174

The loads imposed by modern farm machinery have considerable potential to increase subsoil stress. Within the context of economically viable and environmentally sustainable systems, the practices associated with subsoil damage and methods for avoidance are identified. The greatest potential for damage is on fragile, wet or loosened subsoils combined with high wheel or track loads and contact pressures that create noticeable ruts in the topsoil. In-furrow ploughing increases this potential considerably by placing loads on the subsoil. Measures to avoid this potential involve a whole farm approach and an understanding of the many interactions between cropping systems and machinery. Alternatives to in-furrow ploughing that involve working from the surface and building a protective topsoil are discussed. Key measures to reduce the risk to subsoils involve a clear understanding of tyre load and inflation data and simple on-farm methods of achieving this are suggested. Although avoidance has the potential to reduce the risk, confinement of damage to specific strips in the field is seen as a realistic alternative. Controlled traffic operations, together with precision guidance, offer an economic means by which compaction on the cropped area can be avoided. The most effective route to improvement in soil care across the European Union (EU) is an appropriate management structure coupled with a best practice framework.  相似文献   

Factors affecting fish yield and profit in fish pen culture in flooded ricefields     

Nam Cao Quoc  Nico Vromant  Duong Le Thanh  Frans Ollevier 《Aquaculture International》2012,20(5):827-845

In recent years, a rotational system consisting of two rice crops followed by a fish pen culture during the monsoon flood period was adopted in parts of the flood-prone region of the Mekong Delta. In this paper, we use the survey data from 51 fish pen farmers at Co Do and Vinh Thanh district, Can Tho City, to investigate the factors affecting fish yield and profit in such fish pen culture system. The net yield of all stocked fish varies from 377 to 3,782?kg/ha/crop while the return above variable costs varies from ?5.3 to 9.8 million VND/ha/crop. Low fish price at harvest and the difficulty to sell below market sized fish at a period of oversupply are the main problems for fish pen culture. Fish net yield significantly increases with stocking density and is linked with specific polycultures. Common carp and bighead carp perform best in fish pen culture, both in production and profit considerations. Harvest body mass of common carp is mainly limited by increasing common carp stocking density. Therefore, a stocking density of common carp of about 6,000 fish/ha is recommended to obtain the optimum combination of reasonable body masses, and a good price, as well as a high return above fingerling costs.  相似文献   

Modelling greenhouse climate factors to constrain internal fruit rot (Fusarium spp.) in bell pepper     

Frans  M.  Moerkens  R.  Van Gool  S.  Sauviller  C.  Van Laethem  S.  Luca  S.  Aerts  R.  Ceusters  J. 《植物病害和植物保护杂志》2018,125(4):425-432

Journal of Plant Diseases and Protection - Internal fruit rot in bell pepper is an important fungal disease which results in mycelium growth and/or necrosis on the ovarium and fruit flesh. It is...  相似文献   

Tree biomass estimation in regenerating areas of tropical dry vegetation in northeast Brazil     

Everardo Sampaio  Peter Gasson  Amelia Baracat  David Cutler  Frans Pareyn  Kleber Costa Lima 《Forest Ecology and Management》2010

Allometric equations have been developed for various different vegetation types but have rarely been validated in the field and never for dry tropical forest such as caatinga. In three areas of semi-arid Brazil, with regenerating caatinga vegetation, we measured and weighed twelve hundred individuals of four tree species and used the data to validate equations previously determined in mature caatinga. They and several other equations developed for tropical vegetations overestimate the biomass (B) of trees from the regeneration areas by more than 20%, possibly because these trees have reduced crowns, with lower branch masses. We then determined new allometric equations for them, validating equations for one site against data of the others and pooling the data if they were cross-validated. The best equations were power ones, based on diameter at breast height (D), with little improvement by including height, crown area and/or wood density (Caesalpinia pyramidalis, B = 0.3129D^1.8838; Croton sonderianus, B = 0.4171D^1.5601; Mimosa ophthalmocentra, B = 0.4369D^1.8493; and Mimosa tenuiflora, B = 0.3344D^1.9648 and 0.4138D^1.7718).  相似文献   

Extracting soil microarthropods with olive oil: A novel mechanical extraction method for mesofauna from sandy soils     

Frans J.A. Kuenen  Harmen Venema  Cornelis A.M. van Gestel  Herman A. Verhoef 《European Journal of Soil Biology》2009,45(5-6):496-500

Many soil ecologists still encounter practical difficulties when extracting microarthropods from the soil. Methods using a humidity gradient, established by the use of a heat source, for collecting soil animals appeared not sufficiently efficient in case of sandy soils. For such type of soils, flotation techniques proved more suitable. The use of toxic or aggressive flotation fluids like kerosene, dibromo ethane, carbon tetrachloride and heptane, however, makes these methods less favourable. To circumvent this problem, a novel technique has been developed based on the flotation principle but using olive oil. The method uses a pumping system that injects olive oil at the base of a Perspex column in which the soil sample is suspended in water using a propeller. In this way, intensive contact between oil droplets and the organisms is established, increasing extraction efficiency. After stopping the propeller, animals can easily be collected from the oil floating to the water surface. Adding coloured mites to soil samples was used to determine extraction efficiency of the method. Average (±SD) recoveries of 82.7 ± 7.4% (n = 34) and 89.7 ± 10.0% (n = 10), respectively were obtained when extracting storage mites and predatory mites from a sandy soil.  相似文献