Intra- and interspecific diversity in the response to waterlogging of two co-occurring white oak species (Quercus robur and Q. petraea)

Quercus robur L. and Quercus petraea (Matt.) Liebl. are sympatric oak species with different ecological requirements. Quercus robur is more tolerant to waterlogging than Q. petraea. This ecological divergence may play a role in the maintenance of the two species despite the absence of an insurmountable reproductive barrier between them. We predicted that the genetic architecture of traits related to waterlogging tolerance differs between the species. To gain insight into this architecture in the absence of genetic markers for waterlogging tolerance, we compared populations of seedlings of each species for diversity in the expression of quantitative phenotypic traits induced by severe hypoxia. To determine the capacity for hypertrophied lenticel formation, we applied gas-impermeable mastic to stems of seedlings. Two months after application, the mastic treatment had induced the formation of 3 (+/- 2) cm(-2) hypertrophied lenticels in the absence of root hypoxia. Leaf epinasty during root hypoxia was an early predictor of seedling mortality. Four weeks of waterlogging resulted in greater epinasty in Q. petraea than in Q. robur, but fewer hypertrophied lenticels (16 +/- 6 versus 21 +/- 9 cm(-2)) and adventitious roots (2.7 +/- 4.7 versus 5.2 +/- 5.9). Differences between species in these traits were associated with differences in the frequencies of extreme phenotypes rather than with a generally higher tolerance to waterlogging in Q. robur seedlings.     

Carbon dioxide and energy flux partitioning between the understorey and the overstorey of a maritime pine forest during a year with reduced soil water availability

Carbon dioxide, water vapour and energy fluxes were measured above and within a maritime pine forest during an atypical year with long-lasting reduced soil water availability. Energy balance closure was adequately good at both levels. As compared with what is usually observed at this site the ecosystem dissipated less energy via latent heat flux and more via sensible heat flux. The understorey canopy was responsible for a variable, significant component of the whole canopy fluxes of water vapour and carbon dioxide. The annual contribution of the understorey was 38% (154 mm) of the overall evaporation (399 mm) and 32% (89 mm) of the overall sensible heat flux (274 mm). The participation of the understorey reached 45% of the overall evaporation and 30% of the daytime overall assimilation during significant soil water deficit periods in summertime. Even during winter, understorey photosynthesis was consistent as it compensated soil and understorey respiration. The ecosystem behaved as a sink of carbon, with a negative annual carbon budget (−57 g C m⁻²). However, due to high soil water deficit, the annual ecosystem GPP was 40% less than usually observed at this site. This budget resulted from a sink of −131 g C m⁻² for the overstorey and a source of +74 g C m⁻² for the understorey. Moreover, on an annual basis the overstorey layer contributed to almost two-thirds of the ecosystem respiration. Finally, the effect of long-lasting soil water deficit on the maritime pine forest was found more important than the effect of the heat wave and drought of summer 2003.     

Selection of potential impact odorants and sensory validation of their importance in typical chardonnay wines

The aim of the present study was to validate the joint sensory impact of target compounds on the typicality degree of wine. Target compounds were selected from previous gas chromatography-olfactometry analysis. The preliminary experiment consisted in selecting odorants thought to have a positive effect on typical Chardonnay wines. Two sets of target compounds were chosen with regard to expected relationships between their concentrations and typicality scores. Target compounds were quantified in 20 wines. The second experiment was dedicated to the sensory evaluation of aroma models obtained by supplementation in wines. Three Chardonnay wines with intermediate typicality scores were supplemented with 6- or 10-compound combinations. The typicality degree of 24 samples was assessed by expert orthonasal perception. Wines supplemented with the 6-compound combinations were judged to be intermediate, whereas wines including the 10-compound combinations were considered to be quite representative of the Chardonnay concept. Such results confirm the active contribution of the 10 combined target compounds to typical Chardonnay wines.     

Effects of water-saving irrigation on weed infestation and diversity in paddy fields in East China

The purpose of the article is to investigate the effects of water-saving irrigation on weed infestation and diversity in paddy fields; a two-year field experiment was conducted in Gaoyou Irrigation District, China. The responses of two irrigation treatments, controlled irrigation (CI) and traditional irrigation (TI), were observed and compared. The irrigation water use, yield, weed density, coverage ratio, height, species richness, density, dominant species, Shannon–Wiener index, and Pielou index were examined to analyze the water productivity, weed infestation, and diversity in paddy fields under the two treatments. The results showed that the water conditions were similar before the late tillering stage, and thereafter the CI fields were alternatively dry and wet with shallow standing water and low soil water content, while the TI fields were mostly continuously flooded by deep standing water and high soil water content. Irrigation water use for CI was 46.8% lower than TI. The CI treatment reduced weed density by 38.0%, decreased coverage ratio by 13.8%, and resulted in a 39.0% increase in weed height. Fewer species were found in CI fields than TI fields. The Shannon–Wiener index decreased by 11.5%, and the Pielou index increased by 3.2%. The changed water regime under CI not only impeded the growth of dominant species but also placed the whole weed community at a relatively stable level with reduced weed density. Meanwhile, aquatic weeds were well controlled; however, semi-aquatic weeds became the dominant species. In general, CI effectively reduced the risk of weed outbreaks, and weed diversity also decreased when it reduced irrigation water use.     

The Effect of Six Knotting Methods on the Biomechanical Properties of Three Large Diameter Absorbable Suture Materials

Objective— To evaluate the effect of 6 different knotting methods on the mechanical properties of 3 large absorbable suture materials used in large animal surgery. Study Design— In vitro mechanical study. Sample Population— Knotted suture loops (n=15 per group). Methods— Suture loops were created between two low‐friction pulleys with either 2 polydioxanone, 2 polyglactin 910 or 3 polyglactin 910. Strands were tied using 1 of 6 knotting technique: square knot, surgeon knot, clamped surgeon's knot, sliding half‐hitch knot (HH), Delimar knot and self‐locking knot (SLK). A single cycle to failure test was performed on each suture loop with a distraction rate of 100 mm/min. Failure modes were evaluated and breaking strength, elongation to failure and stiffness were compared. Results— All loops except two HH failed at the knot by acute breaking. The double‐stranded SLK was both stronger and stiffer than all other knots for each suture material. Clamping the first throw of the surgeon knot decreased load to failure significantly (143.11 ± 8.64 N) compared with not clamping (159.21 ± 6.14 N) for polydioxanone. Stiffness and elongation to failure were respectively lower and increased for 2 polydioxanone compared with both polyglactin 910 materials for all knotting techniques. Conclusions— Knotting techniques do influence structural properties of suture loops. The double strand loop conferred stiffer and stronger properties to the SLK Clinical Relevance— Clamping the first throw of polydioxanone should be avoided when tying a suture under tension even using large diameter suture materials. Using a SLK might be considered as a useful alternative when excessive tension is present.     

Selective logging alters allometric relationships of five tropical tree species in seasonal semi-deciduous forests

In selectively logged forests,trees are more likely to expand their diameters(D)at the expense of height(H)growth,resulting in variations in H:D relationships.This study examines how selective logging affects the H:D allometric relationships of five common tree species and whether the effects vary with functional groups(shade-intolerant or shade tolerant)in seasonal semi-deciduous forests.Individuals of five species in a 3000 m^2(0.3 ha)plot were marked and heights and diameters recorded.Most of the species,with one exception,showed greater investment in diameter per increment of height compared to an unlogged forest,possibly because of the greater light available.This study shows the effects of selective logging on species populations as evidenced by increases in H:D ratios.Comparison of forest fragments with different degrees of human impact is important because it allows us to understand the differences in architectural characteristics caused by selective logging.