От чего зависит ширина годичных колец деревьев в центральной части восточно-европейской равнины?
No tree-ring chronologies were reported so far in the International Tree Ring Data Bank for the central part of the East-European Plain. This absence is traditionally explained by the lack of motivation for tree-ring research in this area. Indeed, due to the intense anthropogenic press the old trees are rare in this region and the climatic signal embedded in the ring width is not strong and is always complex. In this study we present the new tree-ring network of 9 ring width chronologies of pine (Pinus sylvestris) up to 297 years long in a large region of about 450 km in diameter in the Central Russia (54–57N, 33–40E) and analyze their climatic response. Tree ring growth in the region is controlled by both temperature and precipitation of vegetation period, and all the analyzed chronologies have significant correlation with summer PDSI values (with coefficients up to r≤0.4). All of them were sampled after the year 2010 when a severe summer drought spread over the European part of Russia. This allowed spatial analysis of 2010 year annual ring (and rings related to the years of other known severe droughts of 20th century) in the context of drought impact on tree growth. This study is a starting point for constructing large tree ring network for further investigation of severity and spatial distribution of droughts in European Russia in the past.
The area covered by boreal forests accounts for ∼16%of the global and 22% of theNorthern Hemisphere landmass. Changes in the productivity and functioning of this circumpolar biome not only have strong effects on species composition and diversity at regional to larger scales, but also on the Earth’s carbon cycle. Although temporal inconsistency in the response of tree growth to temperature has been reported from some locations at the higher northern latitudes, a systematic dendroecological network assessment is stillmissing formost of the boreal zone.Here, we analyze the geographical patterns of changes in summer temperature and precipitation across northern Eurasia>60 °Nsince 1951 AD, aswell as the growth trends and climate responses of 445 Pinus, Larix and Picea ring width chronologies in the same area and period. In contrast to widespread summer warming, fluctuations in precipitation and tree growth are spatially more diverse and overall less distinct. Although the influence of summer temperature on ring formation is increasing with latitude and distinctmoisture effects are restricted to a fewsouthern locations, growth sensitivity to June–July temperature variability is only significant at 16.6% of all sites (p0.01). By revealing complex climate constraints on the productivity of Eurasia’s northern forests, our results question the a priori suitability of boreal tree-ring width chronologies for reconstructing summer temperatures. This study further emphasizes regional climate differences and their role on the dynamics of boreal ecosystems, and also underlines the importance of free data access to facilitate the compilation and evaluation ofmassively replicated and updated dendroecological networks.
Data series of hydrometeorological observations for the Volga Region and Russia as a whole are covered roughly up to 150 past years. The longer series are single. Length of hydrological records for the river runoff is even lesser, up to 50-60 years. The dendrochronological method gives an opportunity to extend exist- ing observational data series into past, if a significant relationship between radial tree growth and a parameter to be reconstructed exists. For the Volga region, we have developed nine pine (Pinus sylvestris L.) tree ring chronologies and one regional master-chronology (MasterTY). Then, the model is created on the basis of the chronologies, and the reconstruction of runoff for Ilet river (1827-2013) and Palmer Drought Severity Index (1825-2013) is undertaken. The results demonstrate the feasibility of such reconstructions for the Volga region. However, more accurate results are obtained in the reconstruction of the long-term dynamics.
Kamchatka’s forests span across the peninsula’s diverse topography and provide a wide range of physiographic and elevational settings that can be used to investigate how forests are responding to climate change and to anticipate future response. Birch (Betula ermanii Cham.) and larch (Larix gmelinii (Rupr.) Kuzen) were sampled at eight new sites and together with previous collections were compared with monthly temperature and precipitation records to identify their climate response. Comparisons show that tree-ring widths in both species are primarily influenced by May through August temperatures of the current growth year, and that there is a general increase in temperature sensitivity with altitude. The ring-width data for each species were also combined into regional chronologies. The resulting composite larch chronology shows a strong resemblance to a Northern Hemisphere (NH) tree-ring based temperature reconstruction with the larch series tracking NH temperatures closely through the past 300 years. The composite birch ring-width series more closely reflects the Pacific regional coastal late summer temperatures. These new data improve our understanding of the response of forests to climate and show the low frequency warming noted in other, more continental records from high latitudes of the Northern Hemisphere. Also evident in the ring-width record is that the larch and birch forests continue to track the strong warming of interior Kamchatka. View Full-Text
One of the key advances in genome assembly that has led to a significant improvement in contig lengths has been improved algorithms for utilization of paired reads (mate-pairs). While in most assemblers, mate-pair information is used in a post-processing step, the recently proposed Paired de Bruijn Graph (PDBG) approach incorporates the mate-pair information directly in the assembly graph structure. However, the PDBG approach faces difficulties when the variation in the insert sizes is high. To address this problem, we first transform mate-pairs into edge-pair histograms that allow one to better estimate the distance between edges in the assembly graph that represent regions linked by multiple mate-pairs. Further, we combine the ideas of mate-pair transformation and PDBGs to construct new data structures for genome assembly: pathsets and pathset graphs.
Many environmental stimuli present a quasi-rhythmic structure at different timescales that the brain needs to decompose and integrate. Cortical oscillations have been proposed as instruments of sensory de-multiplexing, i.e., the parallel processing of different frequency streams in sensory signals. Yet their causal role in such a process has never been demonstrated. Here, we used a neural microcircuit model to address whether coupled theta–gamma oscillations, as observed in human auditory cortex, could underpin the multiscale sensory analysis of speech. We show that, in continuous speech, theta oscillations can flexibly track the syllabic rhythm and temporally organize the phoneme-level response of gamma neurons into a code that enables syllable identification. The tracking of slow speech fluctuations by theta oscillations, and its coupling to gamma-spiking activity both appeared as critical features for accurate speech encoding. These results demonstrate that cortical oscillations can be a key instrument of speech de-multiplexing, parsing, and encoding.
Papers about natural protection territories
Neuronal nicotinic acetylcholine receptors (NNRs) of the α7 subtype have been shown to contribute to the release of dopamine in the nucleus accumbens. The site of action and the underlying mechanism, however, are unclear. Here we applied a circuit modeling approach, supported by electrochemical in vivo recordings, to clarify this issue. Modeling revealed two potential mechanisms for the drop in accumbal dopamine efflux evoked by the selective α7 partial agonist TC-7020. TC-7020 could desensitize α7 NNRs located predominantly on dopamine neurons or glutamatergic afferents to them or, alternatively, activate α7 NNRs located on the glutamatergic afferents to GABAergic interneurons in the ventral tegmental area. Only the model based on desensitization, however, was able to explain the neutralizing effect of coapplied PNU-120596, a positive allosteric modulator. According to our results, the most likely sites of action are the preterminal α7 NNRs controlling glutamate release from cortical afferents to the nucleus accumbens. These findings offer a rationale for the further investigation of α7 NNR agonists as therapy for diseases associated with enhanced mesolimbic dopaminergic tone, such as schizophrenia and addiction