Modelling the limits on the response of net carbon exchange to fertilization in a south-eastern pine forest

Using a combination of model simulations and detailed measurements at a hierarchy of scales conducted at a sandhills forest site, the effect of fertilization on net ecosystem exchange (NEE) and its components in 6‐year‐old Pinus taeda stands was quantified. The detailed measurements, collected over a 20‐d period in September and October, included gas exchange and eddy covariance fluxes, sampled for a 10‐d period each at the fertilized stand and at the control stand. Respiration from the forest floor and above‐ground biomass was measured using chambers during the experiment. Fertilization doubled leaf area index (LAI) and increased leaf carboxylation capacity by 20%. However, this increase in total LAI translated into an increase of only 25% in modelled sunlit LAI and in canopy photosynthesis. It is shown that the same climatic and environmental conditions that enhance photosynthesis in the September and October periods also cause an increase in respiration The increases in respiration counterbalanced photosynthesis and resulted in negligible NEE differences between fertilized and control stands. The fact that total biomass of the fertilized stand exceeded 2·5 times that of the control, suggests that the counteracting effects cannot persist throughout the year. In fact, modelled annual carbon balance showed that gross primary productivity (GPP) increased by about 50% and that the largest enhancement in NEE occurred in the spring and autumn, during which cooler temperatures reduced respiration more than photosynthesis. The modelled difference in annual NEE between fertilized and control stands (approximately 200 1;g 2;C 3;m^?2 y^?1) suggest that the effect of fertilization was sufficiently large to transform the stand from a net terrestrial carbon source to a net sink.     

Immunological structure of the populations of the upper and middle Volga River regions in relation to the causative agent of yersiniosis and its determining factors

The study of the immunological structure of the population in respect of intestinal yersiniosis at territories with different hydrothermal conditions has revealed the presence of a greater immune stratum (23.9% with the average agglutination titer being 1.8 +/- 0.09 log D) in humid areas, such as the region of the Upper Volga, in comparison with dry areas, such as the region of the Middle Volga, where the level of the immune stratum has proved to be twice as low (10.6% with the average agglutination titer being 0.8 +/- 0.1 log D). At both territories no essential differences in the risk of infection between the inhabitants of rural and urban areas, as well as between different professional and age groups have been revealed, with the exception of persons over 51 years of age, among whom the occurrence of seroconversions has proved to be lower.     

Characterization of the endoevaporitic microbial communities in a hypersaline gypsum crust by fatty acid analysis

We have used fatty acid analyses to study the community structure of a layered endoevaporitic microbial community within a gypsum crust that covers the bottom of a saltern evaporation pond in Eilat, Israel. This community, living at a salinity of 218–238 g l⁻¹ total dissolved salts, consists of an upper brown layer dominated by unicellular cyanobacteria, a green layer with filamentous cyanobacteria, a red-purple layer with both Chromatium and Ectothiorhodospira/Halorhodospira type of purple sulfur bacteria, and a black layer in which dissimilatory sulfate reduction occurs. An olive-green layer is sometimes present below the red-purple layer. Analysis by gas chromatography/mass spectrometry of the fatty acid methyl esters prepared from the different fractions showed characteristic patterns in each layer, and these could be related to fatty acid composition data from the literature and to fatty acid analyses of representative halophilic microorganisms isolated from the site. The nature of the fatty acids in the green layer suggests that the cyanobacteria present there use the oxygen-independent pathway for production of unsaturated fatty acids, a pathway only occasionally encountered in filamentous cyanobacteria. The facultative anaerobic nature of the cyanobacteria in the green layer was confirmed by their ability to perform anoxygenic photosynthesis with sulfide as electron donor. Specific signature fatty acids identified for each layer corresponded well with the microscopic and functional analysis of the biota present. Guest Editor: John M. Melack Saline Waters and their Biota     

Photochronographic method for studying the expansion of plasma clouds

A novel method for studying the expansion of plasma clouds is developed. The method makes use of electron-optical cameras operating in the streak and frame-by-frame modes and provides a time resolution of 0.01–1 μs and spatial resolution of 1 mm. The experimental results obtained with this method are presented. Original Russian Text ? A.G. Kravchenko, D.N. Litvin, V.V. Mis’ko, V.M. Murugov, A.V. Senik, V.A. Starodubtsev, 2006, published in Fizika Plazmy, 2006, Vol. 32, No. 2, pp. 166–169.     

Dynamics of the biosynthesis of native chlorophyll forms from initial stages to the completion of the greening process in etiolated leaves]

The succession of the formation of the native chlorophill forms and the development of the energy migration between them was studied by means of the comparison of three spectrum types: absorption, fluorescence and fluorescence excitation, and of their second derivatives. Quantitatively the chlorophyll accumulation in 9 native forms was followed by means of mathematical disintegration of the spectra using computer.     

Chronobiology by moonlight

Most studies in chronobiology focus on solar cycles (daily and annual). Moonlight and the lunar cycle received considerably less attention by chronobiologists. An exception are rhythms in intertidal species. Terrestrial ecologists long ago acknowledged the effects of moonlight on predation success, and consequently on predation risk, foraging behaviour and habitat use, while marine biologists have focused more on the behaviour and mainly on reproduction synchronization with relation to the Moon phase. Lately, several studies in different animal taxa addressed the role of moonlight in determining activity and studied the underlying mechanisms. In this paper, we review the ecological and behavioural evidence showing the effect of moonlight on activity, discuss the adaptive value of these changes, and describe possible mechanisms underlying this effect. We will also refer to other sources of night-time light (‘light pollution’) and highlight open questions that demand further studies.     

Tissue basophils of the thyroid gland in developing amphibia and mammals

The number of mast cells has been established to increase sharply during the metamorphosis of Bufo viridis tadpoles and during the period of postnatal ontogenesis of rats. The data obtained are under discussion to represent mast cell as a system-forming element of thyroid microregion.     

Tissue Turnover Rates and Isotopic Trophic Discrimination Factors in the Endothermic Teleost,Pacific Bluefin Tuna (Thunnus orientalis)

Stable isotope analysis (SIA) of highly migratory marine pelagic animals can improve understanding of their migratory patterns and trophic ecology. However, accurate interpretation of isotopic analyses relies on knowledge of isotope turnover rates and tissue-diet isotope discrimination factors. Laboratory-derived turnover rates and discrimination factors have been difficult to obtain due to the challenges of maintaining these species in captivity. We conducted a study to determine tissue- (white muscle and liver) and isotope- (nitrogen and carbon) specific turnover rates and trophic discrimination factors (TDFs) using archived tissues from captive Pacific bluefin tuna (PBFT), Thunnus orientalis, 1–2914 days after a diet shift in captivity. Half-life values for ¹⁵N turnover in white muscle and liver were 167 and 86 days, and for ¹³C were 255 and 162 days, respectively. TDFs for white muscle and liver were 1.9 and 1.1‰ for δ ¹⁵N and 1.8 and 1.2‰ for δ ¹³C, respectively. Our results demonstrate that turnover of ¹⁵N and ¹³C in bluefin tuna tissues is well described by a single compartment first-order kinetics model. We report variability in turnover rates between tissue types and their isotope dynamics, and hypothesize that metabolic processes play a large role in turnover of nitrogen and carbon in PBFT white muscle and liver tissues. ¹⁵N in white muscle tissue showed the most predictable change with diet over time, suggesting that white muscle δ ¹⁵N data may provide the most reliable inferences for diet and migration studies using stable isotopes in wild fish. These results allow more accurate interpretation of field data and dramatically improve our ability to use stable isotope data from wild tunas to better understand their migration patterns and trophic ecology.