Ecological and methodological drivers of non-stationarity in tree growth response to climate

Radial tree growth is sensitive to environmental conditions, making observed growth increments an important indicator of climate change effects on forest growth. However, unprecedented climate variability could lead to non-stationarity, that is, a decoupling of tree growth responses from climate over time, potentially inducing biases in climate reconstructions and forest growth projections. Little is known about whether and to what extent environmental conditions, species, and model type and resolution affect the occurrence and magnitude of non-stationarity. To systematically assess potential drivers of non-stationarity, we compiled tree-ring width chronologies of two conifer species, Picea abies and Pinus sylvestris, distributed across cold, dry, and mixed climates. We analyzed 147 sites across the Europe including the distribution margins of these species as well as moderate sites. We calibrated four numerical models (linear vs. non-linear, daily vs. monthly resolution) to simulate growth chronologies based on temperature and soil moisture data. Climate–growth models were tested in independent verification periods to quantify their non-stationarity, which was assessed based on bootstrapped transfer function stability tests. The degree of non-stationarity varied between species, site climatic conditions, and models. Chronologies of P. sylvestris showed stronger non-stationarity compared with Picea abies stands with a high degree of stationarity. Sites with mixed climatic signals were most affected by non-stationarity compared with sites sampled at cold and dry species distribution margins. Moreover, linear models with daily resolution exhibited greater non-stationarity compared with monthly-resolved non-linear models. We conclude that non-stationarity in climate–growth responses is a multifactorial phenomenon driven by the interaction of site climatic conditions, tree species, and methodological features of the modeling approach. Given the existence of multiple drivers and the frequent occurrence of non-stationarity, we recommend that temporal non-stationarity rather than stationarity should be considered as the baseline model of climate–growth response for temperate forests.     

Large old trees increase growth under shifting climatic constraints: Aligning tree longevity and individual growth dynamics in primary mountain spruce forests

In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree-level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~5000 Norway spruce (Picea abies [L.] H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed-linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e., competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modeled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (>400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks.     

Studies of γ-glutamyltransferase activity in the brain tissue post mortem

Our experiments showed that the activity of -glutamyltransferase (-GT) did not remarkably change in homogenates of mouse, rat, and bovine brains during the first four days post mortem. In the course of that period, the brain microvessels also retained their -GT activity. -GT of microvessels from bovine brain cortex, solubilized with sodium deoxycholate, was eluted in the void volume V_o when chromatographed on a Sephadex G-200 column with the detergent Triton X-100. In human post mortem brains, the specific activity of -GT in choroid plexi was found to be about five times higher than that in the cerebral cortex, white matter, basal ganglia, pons, and cerebellum but about four times lower than that in the microvessels obtained from the studied brain regions. Our findings suggest that it is possible to study the components of the blood-brain barrier on material from deceased subjects.     

The arrangement of nucleotides in the coding regions of natural templates

Summary The relation of the nucleotide sequences in the coding regions of natural templates and of the short nucleotide sequence in 3 terminus of 16 S ribosomal RNA was found to differ from random pattern. The observation is interpreted in terms of both the ribosomal interactions and the molecular evolution.     

Effect of N-Methyl Substituents in 2-Methoxycarbonylphenylsulfamides on Kinetics and Mechanism of Formation of (1H)-2,1,3-Benzothiadiazin-4(3H)-One-2,2-Dioxides

The cyclization reactions of N-methyl-N’-(2-methoxycarbonylphenyl)sulfamide (1a), N-methyl-N-(2-methoxycarbonylphenyl)-sulfamide (2a), and 2-methoxycarbonylphenylsulfamide (3a) were studied in aqueous amine buffers (butylamine, ethanolamine, morpholine, glycinamide). The dependences observed between the rate constants and buffer concentrations show that the reactions are subject to base catalysis in all the three cases, the decomposition of the tetrahedral intermediate being rate limiting. The ratio of the relative rate constants of the base catalyzed cyclizations reactions of the three derivatives is 1a: 2a: 3a = 1: 20000: 100. The logarithm of rate constants of the base catalyzed cyclization reactions was plotted against the pK_a values of conjugated acids of the individual amines used as the buffers in the cyclization of compound 1a, and the value of the Brönsted coefficient obtained was about 0.1, which means that the proton transfer from the intermediate to the basic buffer component is thermodynamically favorable. The intermediate is a much weaker base, and the reaction is controlled by diffusion. The slope of an analogous dependence for compound 2a gradually decreases from values near to 0.5 to values near to zero, which means that the intermediate formed from compound 2a (pK_a ≈ 9.3) has a pK_a value comparable with that of the acid buffer component.     

Identification ofStaphylococcus andMicrococcus species with the STAPHYtest system

A collection of 216 well-characterized strains ofStaphylococcus, Micrococcus andStomatococcus was examined by a commercially available STAPHYtest system (Lachema, Brno, Czechoslovakia). The results of STAPHYtest agreed with those of conventional tests. The STAPHYtest permitted a clear-cut separation ofStaphylococcus fromMicrococcus andStomatococcus strains and correctly identified 104 of 145 (72%)Staphylococcus strains after 24 h of incubation. However, it allowed the identification only of 19 of 29 validly publishedStaphylococcus species. The STAPHYtest proved to be a simple and rapid system for the separation of staphylococci from micrococci and for the identification of most frequent clinically significant staphylococci.