Effects of increasing landscape heterogeneity on local plant species richness: how much is enough?

Contemporary landscape ecology continues to explore the causes and consequences of landscape heterogeneity across a range of scales, and demands for the scientific underpinnings of landscape planning and management still remains high. The spatial distribution of resources can be a key element in determining habitat quality, and that in turn is directly related to the level of heterogeneity in the system. In this sense, forest habitat mosaics may be more affected by lack of heterogeneity than by structural fragmentation. Nonetheless, increasing spatial heterogeneity at a given spatial scale can also decrease habitat patch size, with potential negative consequences for specialist species. Such dual effect may lead to hump-backed shape relationships between species diversity and heterogeneity, leading to three related assumptions: (i) at low levels of heterogeneity, an increase in heterogeneity favours local and regional species richness, (ii) there is an optimum heterogeneity level at which a maximum number of species is reached, (iii) further increase in spatial heterogeneity has a negative effect on local and regional species richness, due to increasing adverse effects of habitat fragmentation. In this study, we investigated the existence of a hump-shaped relationship between local plant species richness and increasing forest landscape heterogeneity on a complex mosaic in the French Alps. Forest landscape heterogeneity was quantified with five independent criteria. We found significant quadratic relationships between local forest species richness and two heterogeneity criteria indicators, showing a slight decrease of forest species richness at very high heterogeneity levels. Species richness–landscape heterogeneity relationships varied according to the heterogeneity metrics involved and the type of species richness considered. Our results support the assumption that intermediate levels of heterogeneity may support more species than very high levels of heterogeneity, although we were not able to conclude for a systematic negative effect of very high levels of heterogeneity on local plant species richness.     

Comparison of different European rainbow trout populations under intensive production conditions

Growth and carcass quality of European rainbow trout populations were compared in a full sib family test over five experimental periods. In total, 131 full-sib families of 17 different populations, (i.e. 19 500 fish), were included. A special system for family testing in trout was developed. This consisted of separate hatching of single pair matings, separate rearing of families up to marketable size and common fattening under two stocking densities. Thus, growth was studied separately for the rearing and the fattening period. The observed differences in rearing and fattening weight between and within populations were quite distinct and of significance for production and breeding efficiency. Similar ranking of populations after fattening in different years and under different stocking densities indicated that the final weight was highly genetically controlled. Carcass characteristics determined at marketable size showed somewhat smaller differences between populations. Populations with the highest fattening weight did not generally produce the most valuable carcasses. The results are discussed with respect to their impact on breeding strategies.     

Improving cereal grain carbohydrates for diet and health

Starch and cell wall polysaccharides (dietary fibre) of cereal grains contribute to the health benefits associated with the consumption of whole grain cereal products, including reduced risk of obesity, type 2 diabetes, cardiovascular disease and colorectal cancer. The physiological bases for these effects are reviewed in relation to the structures and physical properties of the polysaccharides and their behaviour (including digestion and fermentation) in the gastro-intestinal tract. Strategies for modifying the content and composition of grain polysaccharides to increase their health benefits are discussed, including exploiting natural variation and using mutagenesis and transgenesis to generate further variation. These studies will facilitate the development of new types of cereals and cereal products to face the major health challenges of the 21st century.     

Bodenmikrobiologische Prozesse und Testaceen (Protozoa) als Indikatoren für Schwermetallbelastung

Soil microbial processes and Testacea (Protozoa) as indicators of heavy metal pollution The influence of the emissions from a copper smelter on soil microbial processes was investigated at 4 meadow sites along a concentration gradient in Brixlegg (Austria). The first site is within 300 m of the source, further sites are situated 1125 m, 2425 m and 5900 m from the smelter. Heavy metal pollution close to the smelter induced a decrease of microbial biomass, respiration, dehydrogenase activity and the related enzyme activities in soil samples (5–10 cm soil depth): Protease, alkaline phosphatase, arylsulfatase, actual and potential nitrification. Thus, soil microbial processes in the 5–10 cm layer appear to be directly affected by heavy metals. Regarding the testate amoebae, their low individual and species numbers at 5–10 cm soil depth obstruct clear trends of this animal group. However, comparing the heavy polluted site with the control area, abundances, species numbers and biomass of testate amoebae slightly decreased at the polluted site (5–10 cm). Contrary to the results in the 5–10 cm layer, most soil microbial processes as well as abundances, species numbers and biomass of testaceans in the upper soil (0–5 cm) seem to be more strongly influenced by the supply of organic substrate than by the content of heavy metals in the soil.     

Identification of common antigens in ribosome-rich extracts from Fusobacterium necrophorum

Ribosome-rich extracts (RRE) were prepared by differential and ultracentrifugation from 25 bovine and 6 ovine isolates of Fusobacterium necrophorum (FN) including both biotypes A and B. A pooled rabbit antiserum was prepared against whole-cell and sonicated whole-cell bacterins of F necrophorum isolate FN 3080, and a 2nd pooled rabbit antiserum was prepared against a RRE of FN 3080. The RRE of the 25 bovine isolates were tested against the FN 3080 whole-cell antiserum, using Ouchterlony double-immunodiffusion procedures. One to 3 precipitin lines were observed with the 25 isolates. The individual bovine isolates were found to have lines of identity with 5 to 21 of the other 24 isolates. The 25 bovine isolates and the 6 ovine isolates were then compared, using the FN 3080 RRE antiserum. One to 3 precipitin lines were observed for the 31 isolates with the RRE antiserum, and lines of identity were observed between all 31 of the isolates. These results indicated that common antigens are present in the RRE from a wide variety of F necrophorum isolates including both A and B biotypes.     

Death of a horse infected experimentally with Anaplasma phagocytophilum

A 19-year-old horse that was one of a group of six horses infected experimentally with Anaplasma phagocytophilum for a study of the pathogenesis of equine granulocytic ehrlichiosis died suddenly two days after first showing clinical signs of disease. The clinical signs and laboratory findings observed before its death were similar to all those of the other infected horses, and to previous reports of this disease. A postmortem examination revealed widespread haemorrhaging in its internal organs, and vasculitis and thrombosis in the kidneys. These changes are consistent with disseminated intravascular coagulation, which has previously been reported in human beings infected with the presumably identical agent of human granulocytic ehrlichiosis.     

Accumulation and leaching of the fungicide fentin acetate and intermediates in sandy soils

Accumulation in soil and leaching to groundwater of fentin acetate were studied in the laboratory using two types of Dutch sandy soil differing in organic matter content. Mobility, adsorption, transformation and formation of intermediates were determined in unsaturated soil columns, batch shaking systems and soil incubation systems. Samples were analyzed for monophenyltin, diphenyltin and triphenyltin compounds after methylation. Therefore the transformation products diphenyltin oxide and phenyltin acid were determined separately. Both were detected in soil and pore water. Adsorption indicated that these fungicides are immobile in both types of soil. Nevertheless a small fraction was found in the column leachate. After 1 yr of percolation 5.5 and 20.2% of the dose was recovered as total phenyltin residue in the soil of low and high organic matter content, respectively; all the residue was in the upper 10 cm. The half-life of fentin acetate in soil with 1% organic C varied between 47 and 70 days and between 115 and 140 days in soil with 2% organic C. If fentin acetate is applied annually, one can expect to find an ultimate accumulation level of organotin residues of up to 25% of the annual dose in the plough layer.     

Flavor release measurement from gum model system

Flavor release from a mint-flavored chewing gum model system was measured by atmospheric pressure chemical ionization mass spectroscopy (APCI-MS) and sensory time-intensity (TI). A data analysis method for handling the individual curves from both methods is presented. The APCI-MS data are ratio-scaled using the signal from acetone in the breath of subjects. Next, APCI-MS and sensory TI curves are smoothed by low-pass filtering. Principal component analysis of the individual curves is used to display graphically the product differentiation by APCI-MS or TI signals. It is shown that differences in gum composition can be measured by both instrumental and sensory techniques, providing comparable information. The peppermint oil level (0.5-2% w/w) in the gum influenced both the retronasal concentration and the perceived peppermint flavor. The sweeteners' (sorbitol or xylitol) effect is less apparent. Sensory adaptation and sensitivity differences of human perception versus APCI-MS detection might explain the divergence between the two dynamic measurement methods.