Alexi M. Grachev

Competitive Strength Effect In the Climate Response of Scots Pine Radial Growth In South-Central Siberia Forest-Steppe

ABSTRACT This paper presents a method for classification of trees in groups depending on parameters of the age trend in tree-ring width. The method is tested on a sample containing 194 trees of Scots pine (Pinus sylvestris L.) growing in the forest-steppe zone of the South of Central Siberia. The climatic response of tree-ring width in such climatic conditions is complex. The influence of temperature in May-September is negative (moisture reducing). Warm-season precipitation serving as a source of moisture is a positive factor. Another positive factor is cold-season precipitation as frost protection. We determined the dependence of this response on the local conditions (soil, landscape and anthropogenic factors). The competitive strength of the trees influences both the sensitivity of individual trees to extreme climatic factors and the timing of growth processes. The latter implies the duration of the period of significant response to climate. It appears promising to take this influence into account in dendroclimatic reconstructions by using separate clusters of trees based on the competitive strength and having the maximum response to the reconstructed factor.

Trends In Elemental Concentrations of Tree Rings From the Siberian Arctic

ABSTRACT The biogeochemistry and ecology of the Arctic environment have been heavily impacted by anthropogenic pollution and climate change. We used ICP-MS to measure concentrations of 26 elements in the AD 1300–2000 tree rings of larch from the Taymyr Peninsula in northern Siberia for studying the interaction between environmental change and wood chemistry. We applied a two-stage data reduction technique to identify trends in the noisy measurement data. Statistical assessment of variance of normalized time series reveals pronounced depletion of xylem Ca, Mg, Cl, Bi and Si concentrations and enrichment of P, K, Mn, Rb, Sr and Ba concentrations after ca. AD 1900. The trends are unprecedented in the 700-year records, but multiple mechanisms may be at work and difficult to attribute with certainty. The declining xylem Ca and Mg may be a response to soil acidification from air pollution, whereas increasing P, K, and Mn concentrations may signal changes in root efficiency and excess water-soluble minerals liberated by the permafrost thaw. The changes seem consistent with mounting stress on Arctic vegetation. This study supports the potential of tree rings for monitoring past and ongoing changes in biogeochemistry of Arctic ecosystems related to pollution and permafrost thaw.

Changes in the anatomical structure of tree rings of the rootstock and scion in the heterografts of Siberian pine

The analysis of the anatomical characteristics of tree rings of the Pinus sibirica scions and Pinus sylvestris rootstocks is presented. The main anatomical features maintain the seasonal dynamics characteristic of the reference (ungrafted) trees of scion and rootstock, pointing to the stability of the genetic control of the xylem differentiation. However, various anatomical characteristics are reduced for rootstocks and increased for scions relative to the reference trees. A mechanism consistent with our results is that the graft union zone creates a barrier for the ascending and descending transport of substances, including phytohormones. The reaction of the scion and rootstock to climatic factors is weakened relative to the reaction of the reference trees. Thus, the presumed shift towards phytohormone disbalance reduces the influence of external factors on xylem differentiation. The interannual variation of the individual characteristics of the scions and rootstocks is increased relative to the reference trees, reflecting either the influence of the graft partners on each other or the non-uniform distribution of the growth regulators across the graft union. Thus, heterografts can be used to evaluate the interaction of the internal and external mechanisms of xylem differentiation.

Elemental composition of tree rings: A new perspective in biogeochemistry

Chemical elements that are associated with the ionic composition of the cytoplasm of cells are crucial components of higher plants. They enable various pro� cesses throughout the lifetime of plants associated with cellular energy, operation of a large number of enzymes, etc. (1). Entering the plant from the soil, chemical elements perform their functions in the plant and with its demise close important biogeochemical cycles (2). Longliving woody plants are themselves components of biogeochemical cycles with varying characteristic times: from one year to centuries. Tree rings that form each year in woody plants record the current climatic conditions on one hand, and they accumulate information about longterm changes of their environment (3) on the other. Wood cells mature in one growing season as cell walls lignify, and upon death, they serve as a waterconducting system. Chemical elements that are rigidly linked to the com� ponents of the cell walls of wood and that preserve this link for many decades are thus valuable. They can be used as a potential source of information about the processes and factors that govern their content that took place during the maturing of wood cells. In this paper we present for the first time the changes in biologicallyimportant elements (P, K, Ca, Mg, Sr, Ba, Cl, Si) from 1300 to 2000 AD in the annual rings of larch ( Larix gmelinii Rupr.) from the Taimyr Peninsula (polar boundary of forest vegetation, 72° N). In this study we only consider selected elements that are considered most informative, although the method allowed us to determine the concentration of a total of 40 elements. There are many publications dedicated to the elemental composition of tree rings over short time intervals, however the potential of using the signal of the elements for making long reconstructions of the paleoenvironmental conditions remains unfulfilled. Such a long dendrochemical record for the elements is obtained for the first time. The conditions of tree growth on the permafrost soils of the Taimyr Peninsula are strictly limited by temperature. Wood samples (tree discs) were collected in 2006. Dating of discs was car� ried out using a long master chronology that was pre� viously obtained for this area (4). The actual lifespan of the trees was no more than 350-400 years; for each calendar period 3-6 samples from discs of different ages were measured. Covering the time interval of 700 years was achieved by using samples from both liv� ing and very well preserved dead trees. The total num� ber of samples analyzed from sixteen trees was 351. A single sample contained a 5�year or 10�year period of growth (5 or 10 calendardated tree rings). Chemi� cal analysis was carried out using the method of mass spectrometry with inductively coupled plasma (ICPMS) employing a quadrupole spectrometer Agilent 7500ce. Measurements were made on solu� tions obtained by dissolving wood specimens in con� centrated nitric acid and their subsequent dilution with water. The method of processing wood samples, their dissolution, and the subsequent sample prepara� tion and measurement is described in detail in (5). The longterm average values as well as the range of changes of concentrations of the elements in wood samples are given in the table. The most abundant ele� ments in the wood samples are K + and Ca 2+ , which are important components of the cytoplasm. Ba and Sr, which are the chemical analogs of Ca and Mg, have the lowest concentrations. Based on the temporal vari� ability of all investigated elements, they can be divided into three groups. The first group consists of K and P, which are characterized by the following dynamics: a relatively stable level of concentration during the period from 1300 to 1950 and then a sharp increase in

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.

First geophysical and shallow ice core investigation of the Kazbek plateau glacier, Caucasus Mountains

First-ever ice core drilling at Mt. Kazbek (Caucasus Mountains) took place in the summer of 2014. A shallow ice core (18xa0m) was extracted from a plateau at ~4500xa0m a.s.l. in the vicinity of the Mt. Kazbek summit (5033xa0m a.s.l.). A detailed radar survey showed that the maximum ice thickness at this location is ~250xa0m. Borehole temperature of −7xa0°C was measured at 10xa0m depth. The ice core was analyzed for oxygen and deuterium isotopes and dust concentration. From the observed seasonal cycle, it was determined that the ice core covers the time interval of 2009–2014, with a mean annual snow accumulation rate of 1800xa0mm w. eq. Multiple melt layers have been detected. δ18O values vary from −25 to −5‰. The dust content was determined using a particle sizing and counting analyzer. The dust layers were investigated using scanning electron microscopy and X-ray diffraction analysis. Dust can be separated into two categories by its origin: local and distant. Samples reflecting predominantly local origin consisted mainly of magmatic rocks, while clay minerals were a characteristic of dust carried over large distances, from the deserts of the Middle East and Sahara. The calculated average dust flux over three years at Kazbek was of 1.3xa0mg/cm2 a−1. Neither δ18O nor dust records appear to have been affected by summer melting. Overall, the conditions on Kazbek plateau and the available data suggest that the area offers good prospects of future deep drilling in order to obtain a unique environmental record.

Quantitative characteristics of the phases of winter dormancy of conifer species at a site in Central Siberia

Traditionally the registration of seasonal changes in plant growth and development has been carried out phenologically, i.e., qualitatively using visual inspection. However, since the process of plant acclimatization to winter dormancy involves reversible biochemical and physiological changes at the level of cells, quantitative methods can be applied to determine the duration and the depth of winter dormancy in perennial plants. We used a method based on detecting thermally induced changes in the zero-level fluorescence (TICZF) on needles from four Siberian coniferous trees. Needles of Picea obovata Ledeb. and Abies sibirica Ledeb. recover from the state of winter dormancy much faster than those of Pinus sibirica Du Tour and Pinus sylvestris L. The photosynthetic apparatus in the needles of A. sibirica may be damaged during the spring period, characterized by unstable weather, when after several days of warm weather, the plants prematurely recover from winter dormancy. We conclude that under conditions of climate warming tree, species like A. sibirica may suffer from severe diebacks due to desiccation caused by premature break of winter dormancy.