A Survey of Logging Contract Rates in the Southern European Alps     

Raffaele Spinelli  Rien Visser  Catherine Riond  Natascia Magagnotti 《Small-Scale Forestry》2017,16(2):179-193

A survey of harvesting contracts was conducted in the Alpine regions of France and Italy. The main goal was to produce a benchmark for the harvesting contract rates in the area that may guide forest owners and logging contractors when making their harvesting decisions. The sample included 443 contracts, evenly distributed between France and Italy. The mean tract size was 9.17 ha, while the mean lot size was slightly larger than 500 m³ under bark (ub). Mean removal intensity varied from 70 to 120 m³ ub ha^?1, depending on country and harvesting technique (i.e. ground-based or cable-yarder based). Mean contract rate was 35€ m^?3 ub, but individual contract rates varied significantly between countries and for different harvest techniques. Regression analysis showed that contract rate was strongly affected by tree size, extraction distance and harvest technique. Contrary to expectation, neither tract size nor lot size had any effect on contract rate. This may be explained by the widespread use of mobile operations that are specifically designed for handling small lots and incur minimum relocation cost. The technical factors explored in the study could only explain 40 % of the variability in the dataset, and therefore at least part of the variability must derive from non-technical factors such as local market dynamics and national economics. The study did find significant differences between countries. In particular, ground-based operations were more cost efficient in France, and cable yarder-based operations in Italy.  相似文献   

Effects of increasing days of exposure to prepartum diets on the concentration of certain blood metabolites in dairy cows     

PJ DeGaris  IJ Lean  AR Rabiee  MA Stevenson 《Australian veterinary journal》2010,88(4):137-145

Objective To evaluate the effect of the number of days exposure to a prepartum transition diet on mineral, energy and protein metabolism in dairy cows. Design A prospective cohort study. Procedures The prepartum transition diet consisted of ryegrass pasture, cereal hay, grain, grain by-product, protein meals, BioChlor®, rumen modifiers, minerals and vitamins and contained 13.9% crude protein, 10.0 MJ metabolisable energy/kg and a dietary cation anion difference of −35 meq/kg dry matter. Forty cows were bled bi-weekly from their introduction to the prepartum transition diet until day 35 of lactation. Blood samples were submitted for estimation of a range of metabolites. Cubic smoothed splines were fitted to scatterplots of metabolite concentration as a function of day relative to calving and the area under the curve (AUC) was calculated. Linear regression modelling determined the effect of days exposed, age, body condition score (BSC) and calving day on AUC. Results The prepartum AUC of blood phosphorus and beta-hydroxybutyrate increased and the AUC of blood calcium and cholesterol decreased with increasing days exposed to the diet. The postpartum AUC of beta-hydroxybutyrate and non-esterified fatty acids decreased with increasing days exposed but increased with days exposed × age and days exposed × BCS, respectively. The AUC of other metabolites did not vary significantly with number of days exposed. Conclusions Increasing exposure to the prepartum diet significantly altered the AUC of blood metabolites associated with mineral, energy and protein metabolism in ways consistent with improvements in production and reproduction previously reported and the result suggests links between energy, protein and skeletal metabolism.  相似文献   

Large subclonal variation in Phytophthora infestans populations associated with Ecuadorian potato landraces     

R. A. Delgado  A. R. Monteros‐Altamirano  Y. Li  R. G. F. Visser  T. A. J. van der Lee  B. Vosman 《Plant pathology》2013,62(5):1081-1088

The population of Phytophthora infestans on potato landraces in three provinces (Carchi, Chimborazo and Loja) of Ecuador was analysed. All isolates (n = 66) were of the A1 mating type. Simple sequence repeats (SSR) were used to assess the genetic diversity of the isolates. The P. infestans isolates from the potato landraces grouped in a single clade together with reference isolates belonging to the clonal lineage EC‐1. In the 66 SSR profiles obtained, 31 multilocus genotypes were identified. The 66 isolates constituted 49 different races according to the Solanum demissum differential set ( R1 to R11). The P. infestans population was complex and virulent on 4 to 11 R genes. Analysis showed that the subclonal variation in the Ecuadorian EC‐1 clone is increasing over time and is much larger than clonal variation in lineages in the Netherlands and Nicaragua, suggesting high mutation rates and little or no selection in Ecuador.  相似文献   

ALCEPAS,an onion growth model based on SUCROS87.I. Development of the model     

C. L. M. De Visser 《The Journal of Horticultural Science and Biotechnology》2013,88(3):501-518

Summary

A dynamic simulation model for onion crop growth is presented that is based on SUCROS87, a Simple and Universal Crop Growth Simulator. Onion specific values of parameters and relations of SUCROS87 were established using results from field experiments. The model simulates potential crop growth when weeds, pests, diseases and soil conditions are not limiting growth and there is ample supply of water and nutrients. The model accounts for the influence of sowing date and plant density. The combined influence of environmental factors on leaf growth, bulb initiation and maturity is incorporated. The potential use of the model is discussed.  相似文献   

ALCEPAS,an onion growth model based on SUCROS87. II. Validation of the model     

C. L. M. De Visser 《The Journal of Horticultural Science and Biotechnology》2013,88(3):519-525

Summary

A dynamic simulation model for onion growth at potential production level (ALCEPAS), presented in a previous paper, was validated using data on leaf area index, bulb and green leaf dry-matter production, bulb formation and day of fall-over from independent trials at four locations. The model performance in terms of bulb dry-matter production was good under environmental conditions close to the optimum, but insufficient under stress situations. The model overestimated leaf area index and green leaf dry matter. Bulb formation was simulated satisfactorily, while the time of 50% fall-over was simulated too early at low plant densities.  相似文献   

A methodology for model-based greenhouse design: Part 5, greenhouse design optimisation for southern-Spanish and Dutch conditions     

Bram H.E. Vanthoor  Johannes D. Stigter  Eldert J. van Henten  Cecilia Stanghellini  Pieter H.B. de Visser  Silke Hemming 《Biosystems Engineering》2012,111(4):350-368

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Resection of urachal anomalies in dogs with recurrent lower urinary tract disease     

Judith Visser DVM  Anne Kummeling DVM  PhD DECVS  Marjon A. van Nugteren DVM  Guy C. M. Grinwis DVM  PhD  Bouvien A. W. Brocks DVM  DECVS 《Veterinary surgery : VS》2020,49(1):214-221

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ACVIM consensus statement guidelines for the diagnosis,classification, treatment,and monitoring of pulmonary hypertension in dogs     

Carol Reinero  Lance C. Visser  Heidi B. Kellihan  Isabelle Masseau  Elizabeth Rozanski  Cécile Clercx  Kurt Williams  Jonathan Abbott  Michele Borgarelli  Brian A. Scansen 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(2):549-573

Pulmonary hypertension (PH), defined by increased pressure within the pulmonary vasculature, is a hemodynamic and pathophysiologic state present in a wide variety of cardiovascular, respiratory, and systemic diseases. The purpose of this consensus statement is to provide a multidisciplinary approach to guidelines for the diagnosis, classification, treatment, and monitoring of PH in dogs. Comprehensive evaluation including consideration of signalment, clinical signs, echocardiographic parameters, and results of other diagnostic tests supports the diagnosis of PH and allows identification of associated underlying conditions. Dogs with PH can be classified into the following 6 groups: group 1, pulmonary arterial hypertension; group 2, left heart disease; group 3, respiratory disease/hypoxia; group 4, pulmonary emboli/pulmonary thrombi/pulmonary thromboemboli; group 5, parasitic disease (Dirofilaria and Angiostrongylus); and group 6, disorders that are multifactorial or with unclear mechanisms. The approach to treatment of PH focuses on strategies to decrease the risk of progression, complications, or both, recommendations to target underlying diseases or factors contributing to PH, and PH-specific treatments. Dogs with PH should be monitored for improvement, static condition, or progression, and any identified underlying disorder should be addressed and monitored simultaneously.  相似文献   

FARMERS' KNOWLEDGE AND PERCEPTION OF AGRICULTURAL WETLAND MANAGEMENT IN RWANDA     

N. L. Nabahungu  S. M. Visser 《Land Degradation \u0026amp; Development》2013,24(4):363-374

Most of Rwanda's wetlands are being reclaimed under government schemes with the aim of growing rice as the main crop. In the present study, information on farmers' knowledge and perceptions of agricultural wetland management was collected in Cyabayaga and Rugeramigozi wetlands. The two wetlands were selected as representatives for typical reclaimed wetland agriculture in Rwanda. They provide contrasts in both environmental and social terms. Three tools were used to investigate farmers' knowledge and perception of agricultural wetland management: (i) household survey; (ii) focus group discussions; and (iii) transect walk. The major constraints identified by farmers in the two wetlands were water shortage and lack of availability of improved seeds and high prices of fertilisers. The primary benefits from wetlands for farmers are income generation in Cyabayaga and food security in Rugeramigozi. The most commonly reported concern about the wetlands in the Cyabayaga and Rugerameragozi was that they are a source of malaria. Rice is an important crop in both wetlands, whereas farmers in Cyabahaga wish to continue cultivating rice, Rugeramigozi farmers prefer to grow rice only after it has been tested for its adaptability. Farmers have sufficient knowledge on the causes and the potential solutions to overcome most constraints. They know that soil suitability is closely related to relief. They classify soils by a number of criteria and choose crops accordingly. Any programme designed to address wetland management in the region will have to take account of farmers' knowledge and adopt a holistic view of wetland management. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Genome composition of triploid lily cultivars derived from sexual polyploidization of Longiflorum × Asiatic hybrids (<Emphasis Type="Italic">Lilium</Emphasis>)     

Shujun Zhou  M. S. Ramanna  Richard G. F. Visser  Jaap M. van Tuyl 《Euphytica》2008,160(2):207-215

About 19 cultivars, which had originated from backcrosses between F1 LA (Longiflorum × Asiatic) hybrids (2n = 2x = 24) as female parents and Asiatic cultivars as male parents (2n = 2x = 24), were analyzed with genomic in situ hybridization. 17 of them were triploid (2n = 3x = 36), and two aneuploid (2n = 3x + 1 = 37). The triploid cultivars had resulted from the functional 2n eggs produced by the female parents (F1 hybrids) because first division restitution (FDR) occurred in their meiosis during megasporogenesis. Similarly, the aneuploid cultivars had originated from viable 2n + 1 eggs. The extra chromosome in cultivar 041555 or 041572 resulted from one univalent or one half-bivalent which might have lagged behind when the sister chromatids of the other univalents and half-bivalents were segregating during the FDR process in their LA hybrid parents, respectively. That the majority of cultivars possessed recombinant chromosomes showed that intergenomic recombination might play an important role during the selection of the cultivars directly from BC1 progenies. That five cultivars of the 15 recombinant cultivars only had reciprocal recombinant chromosomes and 10 cultivars had non-reciprocal recombinant chromosomes indicates that the latter are more important. Because 9 of the 10 non-reciprocal recombinant cultivars possessed substitutions for recombinant segments, it also indicated that such substitutions could be an important source for the genetic variation in the sexual triploid BC1 progenies. In such cases there was a potential for the expression of the recessive genes of the backcross parent in a nulliplex (aaa) condition in the substituted segments. Genetic variation resulting from such nulliplex loci might have played a role in the selection of some of the cultivars.  相似文献