Past crops yield dynamics reconstruction from tree-ring chronologies in the forest-steppe zone based on low- and high-frequency components

Interrelations of the yield variability of the main crops (wheat, barley, and oats) with hydrothermal regime and growth of conifer trees (Pinus sylvestris and Larix sibirica) in forest-steppes were investigated in Khakassia, South Siberia. An attempt has been made to understand the role and mechanisms of climatic impact on plants productivity. It was found that amongst variables describing moisture supply, wetness index had maximum impact. Strength of climatic response and correlations with tree growth are different for rain-fed and irrigated crops yield. Separated high-frequency variability components of yield and tree-ring width have more pronounced relationships between each other and with climatic variables than their chronologies per se. Corresponding low-frequency variability components are strongly correlated with maxima observed after 1- to 5-year time shift of tree-ring width. Results of analysis allowed us to develop original approach of crops yield dynamics reconstruction on the base of high-frequency variability component of the growth of pine and low-frequency one of larch

Contribution of xylem anatomy to tree-ring width of two larch species in permafrost and non-permafrost zones of Siberia

Plants exhibit morphological and anatomical adaptations to cope the environmental constraints of their habitat. How can mechanisms for adapting to contrasting environmental conditions change the patterns of tree rings formation? In this study, we explored differences in climatic conditions of permafrost and non-permafrost zones and assessed their influence on radial growth and wood traits of Larix gmelinii Rupr (Rupr) and Larix sibirica L., respectively. We quantified the contribution of xylem cell anatomy to the tree-ring width variability. Comparison of the anatomical tree-ring parameters over the period 1963–2011 was tested based on non-parametric Mann-Whitney U test. The generalized linear modeling shows the common dependence between TRW and the cell structure characteristics in contrasting environments, which can be defined as non-specific to external conditions. Thus, the relationship between the tree-ring width and the cell production in early- and latewood are assessed as linear, whereas the dependence between the radial cell size in early- and latewood and the tree-ring width becomes significantly non-linear for both habitats. Moreover, contribution of earlywood (EW) and latewood (LW) cells to the variation of TRW (in average 56.8% and 24.4% respectively) was significantly higher than the effect of cell diameters (3.3% (EW) and 17.4% (LW)) for the environments. The results show that different larch species from sites with diverging climatic conditions converge towards similar xylem cell structures and relationships between xylem production and cell traits. The work makes a link between climate and tree-ring structure, and promotes a better understanding the anatomical adaptation of larch species to local environment conditions

Modeled Tracheidograms Disclose Drought Influence on Pinus sylvestris Tree-Rings Structure From Siberian Forest-Steppe

Wood formation allows trees to adjust in a changing climate. Understanding what determine its adjustment is crucial to evaluate impacts of climatic changes on trees and forests growth. Despite efforts to characterize wood formation, little is known on its impact on the xylem cellular structure. In this study we apply the Vaganov-Shashkin model to generate synthetic tracheidograms and verify its use to investigate the formation of intra-annual density fluctuations (IADF), one of the most frequent climate tree-ring markers in drought-exposed sites. Results indicate that the model can produce realistic tracheidograms, except for narrow rings (<1 mm), when cambial activity stops due to an excess of drought or a lack of growth vigor. These observations suggest that IADFs are caused by a release of drought limitation to cells formation in the first half of the growing season, but that narrow rings are indicators of an even more extreme and persistent water stress. Taking the example of IADFs formation, this study demonstrated that the Vaganov-Shashkin model is a useful tool to study the climatic impact on tree-ring structures. The ability to produce synthetic tracheidogram represents an unavoidable step to link climate to tree growth and xylem functioning under future scenarios

HOST GENETICS OF SUSCEPTIBILITY Mutations in genes underlying atypical familial mycobacteriosis are not found in tuberculosis patients from Siberian populations

s u m m a r y Objectives: Atypical familial mycobacteriosis (AFM, OMIM #209950) is caused by mutations in genes regulating IL12/IFNG pathway. Some of the mutations exhibit incomplete penetrance, and they have been proposed to be involved in the common (polygenic) predisposition to tuberculosis (TB). We set out to test this hypothesis in two populations from Siberian region of Russia with high prevalence of TB. Material and methods: The prevalence of twelve mutations in IL12/IFNG pathway genes of were analysed in 331 Russians and 238 Tuvinians TB patients and in 279 healthy Russians and 265 healthy Tuvinians. A screening for new mutations and rare polymorphisms was carried out in 10 children with severe generalized TB and severe BCG-vaccine complications using Sanger's bidirectional sequencing. Results: Twelve mutations most commonly identified in AFM patients appeared to be "wild-type" monomorphic in the studied groups. No new mutations or rare polymorphisms were identified by sequencing. However, 15 common single nucleotide polymorphisms were found, none of which was associated with TB after correction for multiple testing. Conclusion: The results of the study contradict with a hypothesis that mutations underlying AFM syndrome are involved in the predisposition to TB

Precipitation reconstruction for the Khakassia region, Siberia, from tree rings

A nested July–June precipitation reconstruction for the period AD 1777–2012 was developed from multi-century tree-ring records of Pinus sylvestris L. (Scots pine) for the Republic of Khakassia in Siberia, Russia. Calibration and verification statistics for the period 1948–2012 show a high level of skill and account for a significant portion of the observed variance (>50%) irrespective of which period is used to develop or verify the regression model. Split-sample validation supports our use of a reconstruction model based on the full period of reliable observational data (1948–2012). Thresholds (25th and 75th percentiles) based on the empirical cumulative distribution of 1948–2012 observed precipitation were used to delineate dry years and wet years of the long-term reconstruction. The longest reconstructed dry period, defined as consecutive years with less than 25th percentile of observed July–June precipitation, was 3 years (1861–1863). There was no significant difference in the number dry and wet periods during the 236 years of the reconstructed precipitation. Maps of geopotential height anomalies indicate that dry years differ from wet years primarily in the location of an anomalous 500-mb ridge approximately over the study area

Small fluctuations in cell wall thickness in pine and spruce xylem: Signal from cambium?

In the conifer tree rings, each tracheid goes through three phases of differentiation before becoming an element of the stem water-conducting structure: division, extension, and cell wall thickening. These phases are long-lasting and separated temporally, especially cell wall thickening. Despite the numerous lines of evidence that external conditions affect the rate of growth processes and the final anatomical dimensions during the respective phases of tracheid differentiation, the influence of the environment on anatomical dimensions during the cell division phase (cambial activity) has not yet been experimentally confirmed. In this communication, we provide indirect evidence of such an effect through observations of the small fluctuations in the latewood cell wall thickness of rapidly growing tree rings, which exhibit a high cell production rate (more than 0.4 cells per day on average). Such small fluctuations in the cell wall thickness cannot be driven by variations in external factors during the secondary wall deposition phase, since this phase overlaps for several tens of latewood cells in the rings of fast-growing trees due to its long duration

Xylogenesis of Scots Pine in an uneven-aged stand of the Minusinsk Depression (Southern Siberia)

Studies on tree-ring formation allow assessing the impact and timing of environmental factors on growth at intra-seasonal resolution. This information is relevant to understand plant acclimatization to current and expected climate changes. Still little is known on how tree age can affect the duration and intensity of annual ring formation. In this study we investigate tree-ring formation of Scots pine (Pinus sylvestris L.) of different age (two classes of 30 and 95 years) from a forest-steppe zone in Southern Siberia. The main tasks were 1) to identify the timing of cambial activity by distinguishing the phases of tracheids division, enlargement, wall thickening and maturation; and 2) to compare the anatomical structure of the tracheids forming the annual rings of the differently aged trees. Observations were performed on stem tissue sampling at weekly resolution from April to September 2014. The results showed different duration of the phases of xylem formation between the groups by up to 1-2 weeks, and that young trees formed a slightly narrower ring width. The tracheids size of the formed cells (i.e. the results of the enlargement phase) was not differed among the groups, whereas the dynamics of the cell-wall thickness showed significant differences. The obtained data can provide references to calibrate processed-based models linking environment to wood formation. In particular, this data allows to benchmarking time-explicit simulated measures of annual ring increment and cell anatomical structures to observation in mature trees growing under natural conditions

A Modified Algorithm for Estimating the Radial Cell Size in the Vaganov-Shashkin Simulation Model

Понимание механизма формирования и роста годичных колец древесных растений под влиянием ведущих факторов внешней среды является одной из самых актуальных проблем современной дендроэкологии. Ускорение или замедление скорости роста дерева в отдельные интервалы сезона определяется совместным влиянием таких климатических факторов, как температура и влажность почвы. С использованием модифицированного алгоритма имитационной модели роста древесных растений Ваганова-Шашкина – VS-осциллографа – в работе моделируется сезонный рост клеток в годичном кольце. Предложен новый математический подход к оценке камбиальной активности хвойных и сезонной клеточной продукции, который был протестирован на образце сосны обыкновенной (Pinus sylvestris L.), отобранном в Хакасии, за период с 1969 по 2008 гг. Благодаря данному подходу удалось разделить влияние климатических и неклиматических внешних факторов на формирование клеток в годичном кольце древесных растенийTo describe the mechanism of tree-ring formation in woody plants influencing by the leading environmental factors is one of the most urgent problems of modern dendroecology. Changing of the tree-ring growth rate at selected intervals in the growing season is determined by the complex influence of climatic factors (e.g. temperature and soil moisture). Using the modified algorithm of the simulation model of growth Vaganov-Shashkin – VS-oscilloscope seasonal growth of cells in tree ring is simulated in the work. New mathematical approach is developed to estimate a cambial activity and seasonal cell production of conifer species. The approach is tested on tree-ring sample of Pinus sylvestris for Khakassian region over 1969-2008. The obtained approach allows to separate a treering growth signal on two components caused by climatic and non-climatic factor

Variation of the hydrological regime of Bele-Shira closed basin in Southern Siberia and its reflection in the radial growth of Larix sibirica

This study analyses dynamics of the hydrological regime of Bele-Shira closed basin and evaluates the potential for using radial growth of Siberian larch (Larix sibirica) for its assessment. We investigated the relationships between different characteristics of the water level variation of Lake Shira, precipitation amount and long-term regional chronologies developed from 56 living trees and 32 dead trees on three sites across this basin. Graphical and correlation analysis indicate that the interannual change (June minus previous June) of the water level of Lake Shira is strongly positively related to the annual sum of precipitation from July to June and the radial growth of larch. It was shown that this hydrological characteristic integrates the current dynamics of the regional precipitation and moisture regime as a whole of the Bele-Shira closed basin on interannual and decadal scales. The water level of Lake Shira fluctuates on a multi-year timescale in synchrony with the cumulative sum of the tree-ring chronology and also has strong positive long-term trend, probably driven by the continual groundwater inflow from neighboring Lake Itkul. Delayed relationships of precipitation and radial growth with the Lake Shira level change are interpreted with reference to a water balance model of the closed basin. Results offer the possibility of reconstructing interannual and decadal variation of the hydrological regime during the last few centuries through regression models using tree-ring chronologies or the dynamics of climatic variables recovered from them

What prevails in climatic response of Pinus sylvestris in-between its range limits in mountains: slope aspect or elevation?

The roles of slope orientation and elevational temperature gradient were investigated for Scots pine (Pinus sylvestris L.) growth in the middle of its growth range, where these factors can significantly modulate microclimate and thus plant growth. We assumed that slope orientation causes more complex and severe effects than elevation because it influences all three main factors of plant growth: light, heat, and moisture. In addition to the total ring width, the earlywood and latewood width and latewood ratio were considered variables that contain information about tree ring growth during the season and wood structure over all tree life span on three sampling sites at different elevations and opposite slopes. Despite the observed dependence of pine growth rate on temperature and solar radiation, the mean latewood ratio is stable and similar between all sampling sites, being presumably defined by the genotype of individual trees. The seasonality of the climatic response of tree growth is bound to spatiotemporal variation of the vegetative season timing due to the elevational temperature lapse and local warming. However, its direction is primarily defined by slope orientation, where southern slope is moisture-limited, even at adjacent sites, and divergent climatic reactions of earlywood (weak moisture-limited in the last decades) and latewood growth (temperature-limited) were revealed on the northern slope