Evaluation and Determination of the Appropriate Method for Assessing Optimum Utilisation Rate of \u3cem\u3eEurotia Ceratoides\u3c/em\u3e in Upland Grasslands of Iran

Determination of optimum utilisation rate for different range species is an important factor in assessing range grazing capacity. The vast rangelands in Iran with diverse vegetation types require an accurate, economic and quick method to determine the optimum utilisation rate for different range species. This experiment was conducted to determine the most appropriate method to determine the optimum utilisation rate for Eurotia ceratoides, which is one of the important grass species in upland grasslands in Iran

Effects of Soil Compaction by Animal Trampling on Growth of \u3cem\u3eAgropyron Repens\u3c/em\u3e

Animal trampling is the most important factor that increases soil compaction beyond the soil elastic property in rangelands under heavy grazing intensities (Lull, 1959). The complicated ecological interactions in a rangeland ecosystem make it difficult to predict the impact of trampling under different conditions. However, soil properties and vegetation composition are sensitive to different grazing management practices. This research, which was carried out in simulated conditions, sought to establish the contribution of soil compaction resulting from animal trampling over a long period to the decline in rangeland condition

Examples of signature (2,2) manifolds with commuting curvature operators

We exhibit Walker manifolds of signature (2,2) with various commutativity properties for the Ricci operator, the skew-symmetric curvature operator, and the Jacobi operator. If the Walker metric is a Riemannian extension of an underlying affine structure A, these properties are related to the Ricci tensor of A

A spinor approach to Walker geometry

A four-dimensional Walker geometry is a four-dimensional manifold M with a neutral metric g and a parallel distribution of totally null two-planes. This distribution has a natural characterization as a projective spinor field subject to a certain constraint. Spinors therefore provide a natural tool for studying Walker geometry, which we exploit to draw together several themes in recent explicit studies of Walker geometry and in other work of Dunajski (2002) and Plebanski (1975) in which Walker geometry is implicit. In addition to studying local Walker geometry, we address a global question raised by the use of spinors.Comment: 41 pages. Typos which persisted into published version corrected, notably at (2.15

Exposure assessment of process-related contaminants in food by biomarker monitoring

Exposure assessment is a fundamental part of the risk assessment paradigm, but can often present a number of challenges and uncertainties. This is especially the case for process contaminants formed during the processing, e.g. heating of food, since they are in part highly reactive and/or volatile, thus making exposure assessment by analysing contents in food unreliable. New approaches are therefore required to accurately assess consumer exposure and thus better inform the risk assessment. Such novel approaches may include the use of biomarkers, physiologically based kinetic (PBK) modelling-facilitated reverse dosimetry, and/or duplicate diet studies. This review focuses on the state of the art with respect to the use of biomarkers of exposure for the process contaminants acrylamide, 3-MCPD esters, glycidyl esters, furan and acrolein. From the overview presented, it becomes clear that the field of assessing human exposure to process-related contaminants in food by biomarker monitoring is promising and strongly developing. The current state of the art as well as the existing data gaps and challenges for the future were defined. They include (1) using PBK modelling and duplicate diet studies to establish, preferably in humans, correlations between external exposure and biomarkers; (2) elucidation of the possible endogenous formation of the process-related contaminants and the resulting biomarker levels; (3) the influence of inter-individual variations and how to include that in the biomarker-based exposure predictions; (4) the correction for confounding factors; (5) the value of the different biomarkers in relation to exposure scenario’s and risk assessment, and (6) the possibilities of novel methodologies. In spite of these challenges it can be concluded that biomarker-based exposure assessment provides a unique opportunity to more accurately assess consumer exposure to process-related contaminants in food and thus to better inform risk assessment

Effects of Burning on Grassland Vegetation Cover on the Northeastern Side of the Alborz Ranges in Iran

Golestan National Park is located on the northeastern side of the Alborz ranges, Golestan province, Iran. Because of the special vegetation cover and being located close to two wet and dry weather areas, this park is vulnerable to fire hazards. Between 1957 and 2004 more than 67 fires have been reported in the park. The international importance of the park requires a careful study on fire effects on vegetation cover, phytomass production, grass diversity and successional process after fires

Water and radiation use efficiency in different developmental stages in four bread wheat cultivars under moisture stress conditions

Abstract This research was conducted in Toroq Experimental field station, Mashhad, Iran, for two successive cropping seasons (2000)(2001)(2002), using split plot experimental design based on complete randomized blocks with three replications. Moisture stress treatments (at seven levels) were assigned to main plots, including: D 1 ( full irrigation), D 2 (no irrigation from oneleaf to double ridge) stage, and in other treatments, no irrigation and preventing rainfall as: D 3 (from one-leaf to floral initiation stage), D 4 (from floral initiation to the commencement of stem elongation or Terminal spikelet), D 5 ( from commencement of stem elongation to flag leaf emergence), D 6 (from flag leaf emergence to anthesis) and D 7 (from anthesis to the soft dough), and four wheat cultivars, namely: Roshan, Qods, Marvdasht and Chamran, were sown in sub plots. The results of combined analysis of variance showed that the effect of moisture stress was significant. Applying D 5 , D 6 and D 7 treatments reduced the grain yield in comparison with control (D 1 ) by 36.7, 22.8 and 45.6, respectively. Severe moisture stress treatments (D 5 and D 7 ) caused a reduction in water use efficiency (WUE) and radiation use efficiency (RUE), due mainly to reduction of dry matter. Based on these results, grain filling (D 7 ) and fast growing (D 5 ) stages of wheat were more sensitive to moisture stress. Genotypic differences were also observed with respect to concerned characteristics. Chamran had a higher moisture tolerance, therefore, greater grain yield as compared with the other cultivars

SUMMER INTERCROPPING SYSTEM IN FORAGE PRODUCTION EFFECT OF SOWING DATE AND NITROGEN FERTILIZER ON SORGHUM (SORGHUM BICOLOR L. VAR. SPEED FEED) FORAGE PRODUCTION IN A SUMMER INTERCROPPING SYSTEM

ABSTRACT. To evaluate the interaction effects of planting date and different levels of nitrogen fertilizer on sorghum (Sorghum bicolor var. Speed feed) forage production, an experiment was conducted in split plots based on a complete randomized block design in Agricultural Research Station of Khorramabad, Lorestan province, Iran. The experimental treatments comprised of three nitrogen fertilizer levels of control (N0), 100 (N1), and 150 kg per hectare (N2), assigned to main plots and three sowing dates of T1 (June, 10 th ), T2 (June 26 th ) and T3 (July 11 th ) assigned to subplots. Results showed that in sum of two harvests, the yield of hay, forage, leaf and shoot hay weigh in second planting date and N2 and N3 level of fertility was higher than all treatments. In the case of quality treatments the percent of crude protein in first harvest had the most amounts in first and second planting date and N1, N2 and N3 fertility levels. Crude fiber percentage in first harvest of second planting date was highest in N1, N2 and N3 levels of fertility. Treatment interactions had not any significant effect for crude fiber. The most ash percent was observed in first harvest and N1, N2 and N3 fertility level. In second harvest time N2 and N3 fertility levels were superior to the rest. Also, fat percentage in first and second planting date and N1, N2 and N3 increased than the control fertility treatment