Anastasia Knorre

Tree ring width, density and ratio of stable isotopes (13C/12C and 18O/16O) in wood and cellulose were determined for larch (Larix sibirica Ledeb.) growing under water deficit conditions in the forest-steppe zone in Central Siberia. Dendroclimatic analysis of the chronologies indicated precipitation to be the most important factor determining tree-ring structure. Precipitation of June is significantly correlated with tree ring

Paleoclimate reconstructions from tree-ring widths and maximum wood density are most successful in localities with extreme climates for particular tree species that are most responsive. Climate proxy records from other, less conventional, tree-ring parameters have been rapidly increasing over the last decade. We assembled a unique dataset of carbon and oxygen isotope ratios of larch tree rings from the northern and southern tree-lines of Siberia, variously sub-sampled and analyzed (whole wood and cellulose & annual and 5-year sequences from individual trees and pooled). Larch samples from the north in Taymyr (Larix gmelinii Rupr.) published by Sidorova et al. (2010) and from the south collected in Khakasia (Larix sibirica Ledeb.) both came from highly temperate continental climates exhibiting similar amounts of precipitation and observed temperature trends. However, the sites differ because temperature is the dominant factor limiting radial tree growth in the north, whereas precipit...

Here, we present the results of an on-going study of tree-ring growth of conifers in Russia’s continuous permafrost zone in northern Siberia, from 61-72°N and 90-148°E. Tree-ring data from a variety of habitats between 20 and 600 m asl with different climate and thermo-hydrological regimes of soils are analyzed. While in some cases up to 60-70% of the year-to-year tree-ring width and maximum latewood density variability can be explained by summer temperature variations alone, we find that the seasonal dynamics of permafrost also plays an important role in defining the overall rate of radial tree growth. Wider rings are generally formed on sites with a deeper active soil layer, which itself depends on the geographical location of a site, as well as its ground vegetation, stand parameters and fire history. Waterlogged permafrost may further act as a source of water for trees under exceptionally dry summer seasons.

Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Montañana 1005, E-50059 Zaragoza, Spain Forest Ecology and Restoration Group, Department of Life Sciences, University of Alcalá, E-28802 Alcalá de Henares (Madrid), Spain Sukachev Institute of Forest SB RAS, Akademgorodok 50/28, 660036 Krasnoyarsk, Russia Institute of Ecology and Geography, Siberian Federal University, pr. Svobodny 82, 660041, Krasnoyarsk, Russia Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, 08028 Barcelona, Spain Department of Forestry, Siberian Federal University, 660041 Krasnoyarsk, Russia Institute of Plant and Animal Ecology SD RAS, 8 Marta Str. 202, Yekaterinburg, 620144, Russia Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Rovira Roure 191, E 25198 Lleida, Spain

ABSTRACT The main goal of this study is to improve our understanding of the influence of a changing climate on trees in extreme conditions by a detailed analysis of the factors controlling tree-ring growth. We investigated forest ecosystems in regions that are very sensitive to climatic changes and where rapid and dramatic environmental and climatic changes are on-going, namely, the high latitude permafrost region in Central Siberia (Russia), the semi-arid dry areas in Central Asia (Uzbekistan) and high-altitude sites in the Alps (Switzerland). Tree-ring parameters studied were ring-width, density, cell number and structure and the ratio of carbon and oxygen isotopes. An important aspect of the work was the characterization of seasonal growth and water supply of trees. Intra-seasonal dynamics of tree-ring formation was correlated with monitored environmental factors, such as air and soil temperature and moisture, permafrost depth and the isotope composition of soil water, of precipitation, and of stream water. Intra-annual and long-term variability of the main tree-ring parameters were compared for the different regions. The results obtained help us to understand better tree-physiological processes valid under contrasting environmental conditions. For instance, the relationship between the onset of cell division in the cambium and the thermo-hydrological soil regime was used to determine the period of the year with the highest influence on the start of tree-ring formation. Seasonally resolved oxygen isotope depth profiles of soil water and concurrent xylem and leaf water measurements show the importance of time-lags between precipitation, leaf processes and growth. The data obtained are important for improving tree-ring growth models and estimating future tree growth under climate change. Funding: SNF SCOPES IZ73Z0_128035

This work is targeted to evaluate the reaction of individual trees against periodic and punctual environmental stressing events with a network of long-term monitoring of tree water/growth-related processes in various geographic and climatic areas. Instrumental measurements of stem circumferential/radial size changes (dRc/dR) using band/point dendrometers and stem sap flow rates (Q) using a trunk segment heat balance method in Scots pine, Siberian larch, and Dahurian larch trees have been carried out at three research sites in Krasnoyarsk Krai, Russia. Analysis of perennial dRc/dR and seasonal Q data obtained in 2015-2019 allows us to characterize the seasonality and features of the tree stem growth and stem water transport rates specific for each of the studied conifer species and on different temporal scales (diurnal, inter/intra-seasonal, and annual). The archived in-situ data are used to verify the efficiency of some process-based BS-and stochastic VS-tree growth and phenology mo...

For species to stay temporally tuned to their environment, they use cues such as the accumulation of degree-days. The relationships between the timing of a phenological event in a population and its environmental cue can be described by a population-level reaction norm. Variation in reaction norms along environmental gradients may either intensify the environmental effects on timing (cogradient variation) or attenuate the effects (countergradient variation). To resolve spatial and seasonal variation in species’ response, we use a unique dataset of 91 taxa and 178 phenological events observed across a network of 472 monitoring sites, spread across the nations of the former Soviet Union. We show that compared to local rates of advancement of phenological events with the advancement of temperature-related cues (i.e., variation within site over years), spatial variation in reaction norms tend to accentuate responses in spring (cogradient variation) and attenuate them in autumn (counterg...

We present an extensive, large-scale, long-term and multitaxon database on phenological and climatic variation, involving 506,186 observation dates acquired in 471 localities in Russian Federation, Ukraine, Uzbekistan, Belarus and Kyrgyzstan. The data cover the period 1890–2018, with 96% of the data being from 1960 onwards. The database is rich in plants, birds and climatic events, but also includes insects, amphibians, reptiles and fungi. The database includes multiple events per species, such as the onset days of leaf unfolding and leaf fall for plants, and the days for first spring and last autumn occurrences for birds. The data were acquired using standardized methods by permanent staff of national parks and nature reserves (87% of the data) and members of a phenological observation network (13% of the data). The database is valuable for exploring how species respond in their phenology to climate change. Large-scale analyses of spatial variation in phenological response can help...

Tree ring width, density and ratio of stable isotopes (13C/12C and 18O/16O) in wood and cellulose were determined for larch (Larix sibirica Ledeb.) growing under water deficit conditions in the forest-steppe zone in Central Siberia. Dendroclimatic analysis of the chronologies indicated precipitation to be the most important factor determining tree-ring structure. Precipitation of June is significantly correlated with tree ring width (TRW) and maximum density (MXD) (r=0.36 and 0.43, p

Forests play a key role in the carbon balance of terrestrial ecosystems. One of the main uncertainties in global change predictions lies in how the spatiotemporal dynamics of forest productivity will be affected by climate warming. Here we show an increasing influence of climate on the spatial variability of tree growth during the last 120 y, ultimately leading to unprecedented temporal coherence in ring-width records over wide geographical scales (spatial synchrony). Synchrony in growth patterns across cold-constrained (central Siberia) and drought-constrained (Spain) Eurasian conifer forests have peaked in the early 21st century at subcontinental scales (∼1,000 km). Such enhanced synchrony is similar to that observed in trees co-occurring within a stand. In boreal forests, the combined effects of recent warming and increasing intensity of climate extremes are enhancing synchrony through an earlier start of wood formation and a stronger impact of year-to-year fluctuations of growin...

Forest fire is among the main environmental factors which determine structure and functioning of boreal ecosystems. In permafrost zone of Siberia (Russia), seasonal thawing depth after fires increases considerably. Then, tree regeneration and ground vegetation recovery lead to increasing thermal insulation of soil surface and, consequently rise of permafrost table. In this study, we estimated the rate of permafrost rise for a larch (Larix gmelinii, Rupr.) stand formed after fire in 1898 and further invaded by Sphagnum mosses. We cross-dated tree-ring width chronologies obtained for tree disks taken at different depth along the larch stem and axial root in peat (further “root”) to define calendar years of formation for the inner (first) and outer (last) tree-rings. There is a good agreement of tree ring growth along the root of each tree: r=0.38–0.98 (81–103 years, p<0.05). A gradual cessation of cambial activity is observed along each larch root with earlier extinction of cambium...

As a complementary field of dendroecology and dendroclimatology, stable isotope analysis in tree rings has a large potential. However, in Siberia tree-ring isotope studies were initiated quite recently and only a few data are available for this vast territory. To understand advantages of using the isotope data in Siberia, we analyzed tree-ring width, density and ratio of stable isotopes (13C/12C, 18O/16O) in larch trees growing in different vegetation zones in Siberia. The data were obtained for four sites located along the regional temperature gradient to cover the territory of natural distribution of larch at low elevations from the northern (72oN) to southern boundaries (54oN): further to the south larch can be found only in mountains. Dendroclimatic analysis of the chronologies indicates carbon isotope data to be the only parameter providing information on July and/or summer precipitation at all the sites. In the south where the role of precipitation becomes especially significa...

Forest fire is one of the most important environmental factors which define forest ecosystem functioning in the continuous permafrost zone in the north of Siberia. Tree-ring width (TRW) and stable isotope (13C/12C and 18O/16O) chronologies from two Larix Gmelinii sites with initially different conditions (wet and dry) and characterized by different fire history (fires in 1852 at wet and 1896 at dry sites, respectively) were considered. It was found that the rate of tree radial growth is enlarged due to the increased depth of seasonally thawing soil layer after fire. This effect is well pronounced during the consequent 30-60 years after the fire event and the length of this period depends on the fire intensity and the type of post-fire ground vegetation. TRW and δ18O are identified to be the most sensitive parameters to the changes of tree growth condition after fire. Correlations between these tree-ring parameters from the two sites shift from significantly positive (r=0.40; p<0....

Bog ecosystems occupy a significant part of Russia and play an important role in the turnover of major biogenic elements [1, 4]. According to latest estimates, the rate of long-term deposition of carbon from the atmosphere provided by bogs is comparable to the rate of carbon deposition provided by basic types of ecosystems [4, 8]. The annual rate of carbon deposition in a sphagnum column can be measured quantitatively if the rates of annual growth and degradation of sphagnum in layers of different ages are known. However, it is very difficult to obtain such data, because the necessary measurements should be performed for many years in bog ecosystems from different natural and climatic zones [2, 3]. Various methods are used to solve this problem. The net ecosystem efficiency of carbon accumulation (NEE) averaged over many years (hundreds and thousands of years) is calculated from peat layer thickness and basal age as determined using the radiocarbon method [4]. In contrast, direct measurements of carbon fluxes over bog ecosystems revealed annual variation in the NEE value [6]. The mean rate of peat accumulation averaged over many years is often determined using the model of vertical growth of bogs, which is based on questionable assumptions [10]. In this work, we suggest a method of estimation of this parameter. This method combines theoretical and experimental approaches to the problem and has the following specific features: (1) it can be applied to a large number of bog ecosystems and (2) it is based on the peatland characteristics that can be measured relatively easily. The bogs where experimental samples were collected were heterotrophic complexes with oligotrophic and mesotrophic ridges and mounds and eutrophic moist depressions. The lands studied in this work were in the middle taiga subzone of the part of Western Siberia located to the west of the Yenisei River (60 ° 45 ′ N, 89 ° 23 ′ E). The sphagnum column age was estimated using the dendrochronological method of determination of the absolute age of pine trees. This method is based on the assumption that the pine hypocotyl position in peat (Fig. 1) corresponds to the time of seed germination [9]. Therefore, the absolute age of a pine tree corresponds to the time of formation of the moss layer above the tree root neck. Pine samples were collected in multiplicates for each age class, starting from seedlings. The height of the surrounding moss layer was measured in each tree starting from hypocotyl. Saw-cuts at the level of root neck were used to determine the absolute age of trees. The measurements at the height of the sphagnum column showed that, in the bogs studied in this work, pine trees of different ages were rooted within the depth range from 8.5 to 65 cm [11]. The maximum depth corresponds to the size of the upper peat-producing layer, which is one of the most active peatland layers in terms of carbon accumulation (i.e., to peat soil per se) [5]. The

ABSTRACT The main goal of this study is to improve our understanding of the influence of a changing climate on trees in extreme conditions by a detailed analysis of the factors controlling tree-ring growth. We investigated forest ecosystems in regions that are very sensitive to climatic changes and where rapid and dramatic environmental and climatic changes are on-going, namely, the high latitude permafrost region in Central Siberia (Russia), the semi-arid dry areas in Central Asia (Uzbekistan) and high-altitude sites in the Alps (Switzerland). Tree-ring parameters studied were ring-width, density, cell number and structure and the ratio of carbon and oxygen isotopes. An important aspect of the work was the characterization of seasonal growth and water supply of trees. Intra-seasonal dynamics of tree-ring formation was correlated with monitored environmental factors, such as air and soil temperature and moisture, permafrost depth and the isotope composition of soil water, of precipitation, and of stream water. Intra-annual and long-term variability of the main tree-ring parameters were compared for the different regions. The results obtained help us to understand better tree-physiological processes valid under contrasting environmental conditions. For instance, the relationship between the onset of cell division in the cambium and the thermo-hydrological soil regime was used to determine the period of the year with the highest influence on the start of tree-ring formation. Seasonally resolved oxygen isotope depth profiles of soil water and concurrent xylem and leaf water measurements show the importance of time-lags between precipitation, leaf processes and growth. The data obtained are important for improving tree-ring growth models and estimating future tree growth under climate change. Funding: SNF SCOPES IZ73Z0_128035

To investigate the variability of primary production of boreal forest ecosystems under the current climatic changes, we compared the dynamics of annual increments and productivity of the main components of plant community (trees, shrubs, mosses) at three sites in the north of Siberia (Russia). Annual radial growth of trees and shrubs was mostly defined by summer temperature regime (positive correlation), but climatic response of woody plants was species specific and depends on local conditions. Dynamics of annual increments of mosses were opposite to tree growth. The difference in climatic response of the different vegetation components of the forest ecosystems indicates that these components seem to be adapted to use climatic conditions during the short and severe northern summer, and decreasing in annual production of one component is usually combined with the increase of other component productivity. Average productivity in the northern forest ecosystems varies from 0.05 to 0.14 ...