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  • Author or Editor: A. Kertész x
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For the investigation of diversity-productivity relationships under natural conditions, we present an operationally feasible measurement scheme explicitly considering the spatial organization of vegetation. We hypothesised that the spatial arrangement of the coexistence of species influences patch-level productivity. To characterise diversity, co-occurrences of species were recorded along oval transects allowing scaling by aggregation between 5 cm and 25 m. Productivity was characterised by field radiometric measurements, calibrated for leaf area and biomass, arranged in a sampling scheme scalable between 20 cm and 50 m. All data were collected along a slight resource gradient in the Stipa-Bouteloua (upland) community of the northern mixed-grass prairie in Grasslands National Park, Saskatchewan. We found a wide range of correlations (Kendall's . between -0. 2 and 0. 9) between various measures of diversity (species richness, local species combinations) and productivity (average and variability of leaf-area index) as a function of sampling unit size. For field assessment of patch-level composition and functioning, we recommend to use samples at the spatial resolution corresponding to the maximum number of local species combinations as an appropriate scale for comparison. We demonstrate how our sampling methodology can be considered for possible process-oriented inference about diversity and productivity. To characterise diversity-productivity relationships for long-term monitoring and prediction of plant community structure and functioning, scalable, repeatable, non-destructive observations should be applied.

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Community Ecology
Authors: F. Samu, F. Kádár, G. Ónodi, M. Kertész, A. Szirányi, É. Szita, K. Fetykó, D. Neidert, E. Botos and V. Altbäcker

Recent environmental and land use changes have made wildfires more frequent in natural habitats of the Kiskunság Sand Ridge on the Hungarian Plain. In a study initiated 2.5 years after an extensive fire that destroyed half of the area of a sand grassland — juniper, poplar forest steppe habitat, we assessed the effects of fire on two generalist arthropod groups: spiders and carabid beetles, as well as on the vegetation. Utilizing the natural experiment situation, samples were taken by pitfalls and suction sampling during a 1.5 years period in four 1 ha blocks, two of which were on the burnt part of the habitat, and two in the unburnt control. At the time of the investigation, in the burnt area the vegetation in the grass layer showed a quick but not complete recovery, while the canopy layer of the juniper bushes burnt down with no sign of regeneration. Carabid beetles and spiders showed differences in recovery after fire. In the carabid assemblages of the burnt parts — compared to the unburnt control — there were over three times more beetles, out of which significantly more represented the macropterous life form and granivorous feeding strategy. There was a higher ratio of pioneer species and a simplified assemblage structure in the burnt area, which meant that the conservation value of the carabid assemblage became lower there. In contrast, for the spider assemblage quantitative changes in abundance and species numbers were not significant, and the differences in species composition did not lead to a decrease in conservation value. Spider species in the burnt plots could not be described as pioneer species, rather they had ecological characteristics that suited the changed vegetation structure. Comparing the two groups, to repopulate the burnt areas, dispersal abilities proved to be more limiting for carabids. However, in both groups a strong assemblage level adaptation could be observed to the postfire conditions. In spiders, species with a stratum preference for the grass layer prevailed, while in carabids individuals with granivore strategy gained dominance. Thus, despite the differences in their speed, basically both assemblages tracked vegetation changes. The effect of future fires will depend on their scale, as well as land-use practices, such as grazing, that interact with fire frequency and recovery. If extensive fires in the future permanently change the vegetation, then it would also lead to a fundamental change in the arthropod fauna.

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Cereal Research Communications
Authors: Z. Áy, Z. Kerényi, A. Takács, M. Papp, I. Petróczi, R. Gáborjányi, D. Silhavy, J. Pauk and Z. Kertész

The reliable monitoring of field virus infections of crop species is important for both farmers and plant breeders. The aim of this study was to detect virus infections of winter wheat in the 2006/2007 season. Twelve well-known winter wheat varieties were sown on two different dates (11 th of October and 3 rd of November 2006). Leaves of two individuals from each genotype were collected on 23rd of April 2007 to detect the virus infections ( Barley stripe mosaic virus — BSMV, Barley yellow dwarf virus — BYDV-PAV, Wheat dwarf virus — WDV and Wheat streak mosaic virus — WSMV) after an extra mild autumn- and wintertime. Virus infections were detected by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). The aphid-transmitted BYDV-PAV was found frequently whereas other viruses were presented very rarely or were not detected. Forty-six per cent of the tested wheat plants proved to be infected by BYDV-PAV in ELISA, while using PCR, the virus infections with BYDV-PAV was found in 58% of the samples. Further, these results suggest that the optimal sowing time is critical in the control of cereal virus diseases, and additionally, that wheat varieties respond to the virus infections differently.

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