SibFU scientists have proved the prospects of cedar for climate research
A scientific team of SibFU scientists led by Academician Yugene Vaganov, scientific director of the world-class climatic Yenisey Siberia REC, together with Indian colleagues, conducted a unique study of the anatomical structure of Siberian cedar wood. The measurement of cedar wood cells has become the key to identifying the relationship between the growth of this tree in the highlands and the climate. Scientists have refuted the earlier opinion about the uselessness of cedar wood for dendrochronological analysis.
Siberian, i.e. a cedar pine, is familiar to most people as Siberian cedar — one of the most widespread coniferous species in the taiga forests of Russia. The ecological and economic importance of cedar forests is great, and it would seem that the growth of this species and the factors affecting it should be widely investigated. However, dendrochronological studies, the object of which is the cedar, are conducted very rarely.
“The impact on tree growth of rapidly changing environmental factors, such as climate, leads to the same rapid fluctuations in the width of annual rings. For example, in the Siberian larch, known for its sensitivity, in harsh conditions, neighboring rings may differ in width by 50%. This is an average value for the entire lifespan of a tree, and during extreme events, the growth may increase or decrease several times compared to the previous year. However, some types of trees, including European and Siberian cedar pines, have more stable growth. Their average sensitivity can be 10% or less even at the borders of the range, where the climate impact should be strong. Moreover, in these species, the rings have a more uniform structure, which means that it is difficult to use measurements of some other indicators of the annual ring. Therefore, the Siberian cedar is considered unpromising from the point of view of dendrochronology. But we still found a way to decipher the information contained in its rings,” — explained Dina Zhirnova, head of the dendroecological laboratory of the Khakass Technical Institute, a branch of Siberian Federal University (Abakan).
In this laboratory, in addition to traditional dendrochronological studies, a lot of attention is paid to a newer related direction — the analysis of the anatomy of wood on the scale of individual cells. Obtaining anatomical data involves taking samples, taking very thin sections of wood, photographing them at high magnification, and measuring them. This is a very long, painstaking and costly process, so there are not many scientific teams in the world specializing in the field of wood anatomy. As a rule, these measurements are limited to several decades. Moreover, the anatomical measurements obtained in the laboratory for several centuries are unique.
Coniferous wood consists of tracheids — cells that look like thin long tubes, lined up in even rows. Scientists count all the cells in such a row under a microscope on slices of wood and measure their size. In the future these measurements may provide a more detailed description of the conditions during the growth of the annual ring. On the other hand, a large number of variables taken into account creates problems, since they can depend on each other. Since the quantitative anatomy of wood began to form only with the development of information technology, its methodology is in the process of development and justification.
“The problem is that the processes of growth and development of wood cells not only overlap in time, but also affect each other. Therefore, in different "anatomical" chronologies, information about the environment partially overlaps, and it is necessary to select methods to divide it into components. If the season has relatively favorable conditions, then the structure of the ring will be stable, ensuring optimal performance of the functions of the wood tissue. Under stress, on the contrary, all growth processes are inhibited and a narrow ring with deviations in the cellular structure is formed. Based on these patterns, we were able to describe the dependences between different cell indicators in the form of functions, and use them to separate the climatic signal recorded in these indicators,” — said Elena Babushkina, scientific consultant of the dendroecological laboratory, director of Khakass Technical Institute, a branch of SibFU.
Scientists studied the anatomy of the Siberian cedar on the upper border of the forest near the Sayan Pass (Western Sayan). Cedar is a long-lived tree, so the series of anatomical measurements they obtained have a record duration of almost five centuries (495 years). It sounds interesting that in the cellular chronologies of Siberian stone pine the “rapid” fluctuations turned out to be small. On the other hand, it turned out that the increase and especially the structure of the annual ring captures well climate changes lasting decades or more. Based on the proposed method, the research team built models for the reconstruction of the temperature and duration of the warm season. In the long term, these reconstructions can be useful in planning an agricultural development strategy — in particular, to predict which types and varieties of crops will become the most successful due to ongoing climate change. It will also be possible to assume the amount of precipitation, droughts, the duration of the growing season of cultivated plants.