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

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

Forward Modeling Reveals Multidecadal Trends in Cambial Kinetics and Phenology at Treeline

Significant alterations of cambial activity might be expected due to climate warming, leading to growing season extension and higher growth rates especially in cold-limited forests. However, assessment of climate-change-driven trends in intra-annual wood formation suffers from the lack of direct observations with a timespan exceeding a few years. We used the Vaganov-Shashkin process-based model to: (i) simulate daily resolved numbers of cambial and differentiating cells; and (ii) develop chronologies of the onset and termination of specific phases of cambial phenology during 1961–2017. We also determined the dominant climatic factor limiting cambial activity for each day. To asses intra-annual model validity, we used 8 years of direct xylogenesis monitoring from the treeline region of the Krkonoše Mts. (Czechia). The model exhibits high validity in case of spring phenological phases and a seasonal dynamics of tracheid production, but its precision declines for estimates of autumn phenological phases and growing season duration. The simulations reveal an increasing trend in the number of tracheids produced by cambium each year by 0.42 cells/year. Spring phenological phases (onset of cambial cell growth and tracheid enlargement) show significant shifts toward earlier occurrence in the year (for 0.28–0.34 days/year). In addition, there is a significant increase in simulated growth rates during entire growing season associated with the intra-annual redistribution of the dominant climatic controls over cambial activity. Results suggest that higher growth rates at treeline are driven by (i) temperature-stimulated intensification of spring cambial kinetics, and (ii) decoupling of summer growth rates from the limiting effect of low summer temperature due to higher frequency of climatically optimal days. Our results highlight that the cambial kinetics stimulation by increasing spring and summer temperatures and shifting spring phenology determine the recent growth trends of treeline ecosystems. Redistribution of individual climatic factors controlling cambial activity during the growing season questions the temporal stability of climatic signal of cold forest chronologies under ongoing climate change

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

Intra- and Inter-Annual Growth Patterns of a Mixed Pine-Oak Forest under Mediterranean Climate

Temperature and precipitation variability throughout the year control the intra-annual dynamics of tree-ring formation. Physiological adaptation of trees to climate change is among the key issues to better understand and predict future forest performance and composition. In this study, we investigated the species’ coexistence and performance of Scots pine and pubescent oak growing in a mixed sub-Mediterranean forest in the northeast of the Iberian Peninsula. We assessed intra-annual cumulative growth patterns derived from band dendrometers during four consecutive growing seasons and long-term changes in basal area increment for the period 1950–2014. Our results revealed that Scots pine followed an intra-annual bimodal growth pattern. Scots pine growth was mainly limited by water availability at intra-annual, interannual and decadal time scales, which resulted in a negative long-term growth trend. Conversely, oak displayed a unimodal growth pattern, which was less climatically constrained. A significant increase in basal area of oak denotes an overall better potential acclimation to prevailing climatic conditions at the expenses of a higher risk of physiological failure during extreme climate events

Intra- and Inter-Annual Growth Patterns of a Mixed Pine-Oak Forest under Mediterranean Climate

Temperature and precipitation variability throughout the year control the intra-annual dynamics of tree-ring formation. Physiological adaptation of trees to climate change is among the key issues to better understand and predict future forest performance and composition. In this study, we investigated the species’ coexistence and performance of Scots pine and pubescent oak growing in a mixed sub-Mediterranean forest in the northeast of the Iberian Peninsula. We assessed intra-annual cumulative growth patterns derived from band dendrometers during four consecutive growing seasons and long-term changes in basal area increment for the period 1950–2014. Our results revealed that Scots pine followed an intra-annual bimodal growth pattern. Scots pine growth was mainly limited by water availability at intra-annual, interannual and decadal time scales, which resulted in a negative long-term growth trend. Conversely, oak displayed a unimodal growth pattern, which was less climatically constrained. A significant increase in basal area of oak denotes an overall better potential acclimation to prevailing climatic conditions at the expenses of a higher risk of physiological failure during extreme climate events

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

Image_1_Modeled Tracheidograms Disclose Drought Influence on Pinus sylvestris Tree-Rings Structure From Siberian Forest-Steppe.JPEG

<p>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.</p

Image_2_Modeled Tracheidograms Disclose Drought Influence on Pinus sylvestris Tree-Rings Structure From Siberian Forest-Steppe.JPEG

<p>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.</p