Indicators of biodiversity, what do they indicate? - Lessons for conservation of cryptogams in oak-rich forest

In the Nordic countries, sets of Indicator (Signal) species, predominantly cryptogams, have been used as one measure to find forest stands which may harbour Red List species. Such data could potentially also be used to prioritise among stands for protection as nature reserves. We studied if the number of Signal species indicates the number of Red List species in oak-rich mixed forest in south Sweden. We also explored if species richness of the investigated groups is correlated with the number of Red List or Signal species. In 25 stands, we surveyed epiphytic and epixylic bryophytes and lichens, ground-floor bryophytes, and wood-living fungi. We studied correlations for two datasets; (1) all forest species and (2) deciduous forest specialists. When relating the number of Signal species to the number of Red List species for each taxon and in total, a significant correlation was found for temperate deciduous forest lichens. The number of Signal species was further significantly correlated to total species richness for lichens (all forest species) and for wood-living fungi (both datasets). The number of Red List lichens was correlated to total lichen richness (deciduous forest species). Signal species seem not to be unequivocal in prioritising potential reserves among valuable oak-rich woodlands and surveys by Red List species experts may be needed. Signal species may be more useful for finding relatively valuable sites in a matrix of production forest. Moreover, Signal species seem to be useful surrogates for total cryptogam species richness.     

Handling missingness when modeling the force of infection from clustered seroprevalence data

Modeling infectious diseases data is a relatively young research area in which clustering and stratification are key features. It is not unlikely for these data to have missing values. If values are missing completely at random, the analysis on the complete cases is valid. However, in practice this assumption is usually not fulfilled. This article shows the effect of ignoring missing data in modeling the force of infection of the bovine herpesvirus-1 in Belgian cattle and proposes the use of weighted generalized estimating equations with constrained fractional polynomials as a flexible modeling tool.     

Sampling and monitoring of biogenic emissions by eucalyptus leaves using membrane extraction with sorbent interface (MESI)

Membrane extraction with sorbent interface (MESI) has been applied to monitor plant fragrance volatiles emitted into indoor air. The main components of the MESI system are a membrane module and a trap, which can be connected directly to a GC or GC-MS for simultaneous multicomponent extraction and monitoring. A polydimethylsiloxane (PDMS) membrane and two different traps, PDMS and Tenax, as well as a DC current supply for trap desorption have been applied in this research. After the membrane module is placed in contact with the plant, the MESI/GC-MS provides semicontinuous characterization of volatile compounds emitted. The MESI device has been applied to monitor the biogenic volatile organic compounds released during the first 8 h after a branch was cut from a Eucalyptus dunnii tree. The study demonstrates that the MESI system is a simple and useful tool for monitoring changes in emission processes as a function of time.     

Lachgas(N2O)-Freisetzung durch Streptomyces nitrosporeus in einem sandigen Lehmboden in Abhängigkeit von pO2, pH und Angebot an leicht mineralisierbarem Kohlenstoff

Nitrous oxide (N₂O) release by Streptomyces nitrosporeus in a sandy loam soil as affected by pO₂, pH and amount of easily decomposable organic carbon In model experiments under defined conditions (80%WHC, 300 μg nitrate-N g^?1 dry soil, 30°C) the effect of pO₂, pH and addition of easily decomposable organic matter on nitrous oxide production by Streptomyces nitrosporeus DSM 40023 from a sterilized sandy loam soil was studied. This streptomycete reduces nitrate to N₂O but not to N₂. The strain was inoculated into a sterilized sandy loam soil (pH 6), enriched with nitrate and incubated at approximately 20 and 10% (v/v) O₂ for 26 days. In another series of experiments the pH was increased with NaOH-solution up to pH 7 or the soil was enriched with pulverized leaves (1%) to increase mineralization activity and the demand for electron acceptors. In the headspace the concentration of O₂, CO₂ and N₂O was analysed by GC. The soil concentration of NO₃^?, NO₂^? and NH₄⁺ was measured as well as the pH value. The population density was determined by the plate count method. At a decreased oxygen concentration of about 2.5% (v/v) in the headspace, S. nitrosporeus increased the release of N₂O. In the experiments with an initial oxygen concentration of approximately 20% (v/v) this threshold of about 2.5% /(v/v) O₂ was hardly reached and consequently only little N₂O was produced. Apparently, S. nitrosporeus uses O₂ in preference to nitrate, which is characteristical of nitrate respiration. A pH increase from pH 6 to 7 reduced the lag phase significantly and increased the rate of oxygen consumption, CO₂ release and N₂O production. Maximum nitrous oxide production was reached after 13 days. The result indicated that streptomycetes like S. nitrosporeus may use nitrate alternativly to O₂ to maintain energy conservation (ATP synthesis) with the release of N₂O. So far, nothing is known about the role of streptomycetes in contributing to N₂O production in natural soils.     

Effects of thiopental sedation on learning and memory

Subjects who were administered thiopental showed a loss of memory for events discussed while they were under sedation. We tested the subjects for recognition memory of pictures and recall of associated pairs of letters and words, and found that the subsequent memory loss was correlated with the concentration of thiopental in the venous blood at the time the material was learned. Retention did not appear to be state-dependent because the subject, while under sedation, could recall material learned prior to sedation, and because recall was not facilitated by reinstatement of the sedation.