Approximation by the Dickman distribution and quasi-logarithmic combinatorial structures

Quasi-logarithmic combinatorial structures are a class of decomposable combinatorial structures which extend the logarithmic class considered by Arratia, Barbour and Tavar\'{e} (2003). In order to obtain asymptotic approximations to their component spectrum, it is necessary first to establish an approximation to the sum of an associated sequence of independent random variables in terms of the Dickman distribution. This in turn requires an argument that refines the Mineka coupling by incorporating a blocking construction, leading to exponentially sharper coupling rates for the sums in question. Applications include distributional limit theorems for the size of the largest component and for the vector of counts of the small components in a quasi-logarithmic combinatorial structure.Comment: 22 pages; replaces earlier paper [arXiv:math/0609129] with same title by Bruno Nietlispac

Asymptotic density in quasi-logarithmic additive number systems

We show that in quasi-logarithmic additive number systems \mycal{A} all partition sets have asymptotic density, and we obtain a corresponding monadic second-order limit law for adequate classes of relational structures. Our conditions on the local counting function p(n) of the set of irreducible elements of \mycal{A} allow situations which are not covered by the density theorems of Compton [6] and Woods [15]. We also give conditions on p(n) which are sufficient to show the assumptions of Compton's result are satisfied, but which are not necessarily implied by those of Bell and Burris [2], Granovsky and Stark [8] or Stark [14

Soil biological quality in short- and long-term field trials with conventional and organic fertility input types

Soils of the DOK trial and three other field trials with manure input were analysed for effects on soil biology. While long-term effects indicate a new steady state at the DOK trial site, differences at the other field trials suggest that fresh manure at the Bonn trial and chicken manure at the UK sites are at least temporarily advantageous, probably due to their relatively fast mineralization

Klimafreundlicher Bioackerbau auf schweren Böden (Exaktversuch Frick)

Versuchsfragen Langfristige Auswirkungen auf Bodenfruchtbarkeit und Ertrag bei: ❯ Reduzierter Bodenbearbeitung vs Pfl ug ❯ Vollgülle vs Mistkompost/Gülle ❯ Mit vs ohne biologisch-dynamische Präparate Questions expérimentales Conséquences à long terme sur la fertilité du sol et le rendement en cas de: ❯ Travail réduit du sol par rapport au labourage ❯ Lisier complet vs. compost fumier/lisier ❯ Avec ou sans préparation biodynamique

Asymptotic density in quasi-logarithmic additive number systems

This paper has been withdrawn by the author; a revised version is part of the author's phd-thesis "Quasi-logarithmic structures" (Zurich, 2007)

Effects of conventionally bred and Bacillus thuringiensis (Bt) maize varieties on soil microbial biomass and activity

Abstract Genetically modified (GM) maize containing genes from the soil bacterium Bacillus thuringiensis (Bt) was cultivated on 29% of the total maize production area worldwide in 2009. Most studies to date compare Bt-maize varieties with their near isogenic lines; however, there is little information on the variability of conventional maize breeding lines and how the effects of Bt varieties are ranked within. In our study on the potential risks of Bt-maize varieties, we analyzed tissue quality and compared the effects of ten conventional and GM maize varieties on soil microbiological properties in a replicated climate chamber experiment. All maize varieties were cultivated twice in the same soil microcosm. Shoot yields and soluble C in leaf tissue of Bt varieties were higher than the ones of non-Bt. Soil dehydrogenase activity was reduced by 5% under Bt varieties compared to non-Bt, while most of the other soil microbial properties (soil microbial biomass, basal respiration) showed no significant differences between Bt and non-Bt varieties. The leaves and roots of one Bt variety were decomposed to a greater extent than the ones of its near isogenic line; the conventional breeding lines also showed higher values. Changes in crop and soil parameters were found when comparing the first and the second crops, but the effects of repeated cropping were the same for all tested varieties. For the studied parameters, the variation among non- Bt-maize varieties was similar to the difference between Bt and non-Bt varieties

Re-establishment of suppressiveness to soil- and air-borne diseases by re-inoculation of soil microbial communities

The aim of this study was to investigate the potentials and limitations in restoring soil suppressiveness in disturbed soils. Soils from three sites in UK and Switzerland (STC, REC, THE) differing in their level of suppressiveness to soil-borne and air-borne diseases were γ-irradiated and this soil matrix was re-inoculated with 1% (w/w) of either parent native soil or native soil from the other sites (‘soil inoculum’). Suppressiveness to air-borne and soil-borne diseases was quantified by means of the host–pathogen systems Lepidium sativum (cress)–Pythium ultimum, an oomycete causing root rot and seedling damping-off, and Arabidopsis thaliana–Hyaloperonospora parasitica, an oomycete causing downy mildew. Soil microbial biomass, activity and community structure, as determined by phospholipid fatty acid (PLFA) profiles, were measured in native, γ-irradiated, and re-inoculated soils. Both, L. sativum and A. thaliana were highly susceptible to the pathogens if grown on γ-irradiated soils. Re-inoculation completely restored suppressiveness of soils to the foliar pathogen H. parasitica, independently of soil matrix or soil inoculum, whereas suppressiveness to P. ultimum depended on the soil matrix and, to a lesser extent, on the soil inoculum. However, the soil with the highest inherent suppressiveness did not reach the initial level of suppressiveness after re-inoculation. In addition, native microbial populations as defined by microbial biomass, activity and community structure, could not be fully restored in re-inoculated soils. As for suppressiveness to P. ultimum, the soil matrix, rather than the source of soil inoculum was identified as the key factor for re-establishing the microbial community structure. Our data show that soils do not or only slowly fully recover from sterilisation by γ-irradiation, indicating that agricultural soil management practices such as soil fumigation or heat treatments frequently used in vegetable cropping should be avoided