This study explored whether consistent differences can be found between early-wood and late-wood in terms of elemental content of tree rings. The species to study was Pinus sylvestris L. growing within an even-aged stand planted during the early 1970s in eastern Siberia. The wood specimens were extracted from the north and south sides of trees and subsequently scanned through an X-ray fluorescent facility Itrax Multiscanner. A sequence of relatively wide tree-rings was chosen for the analysis. The scanning data on a number of elements (Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, Sr, and Hg) were split into early-wood and late-wood data for each year of growth. The early- and late-wood data in the same ring were analyzed for basic statistics against each other as well as against available meteorological data. In the northern direction, the elements Al, Si, P, Cl, Cu, and Zn are always more abundant in the late-wood, while Ca, Fe, and Sr are always more abundant in the early-wood. What is important is how the differences for P, Ca, Fe, Cu, Zn, and Sr were always significant. The calcium content in the early-wood was the most consistently reflective regarding the meteorological data for the early summer (June). In some trees, the late-wood K content was well correlated with the Vysotskii–Ivanov climatic index. In the southern direction, Cu and Zn were always more abundant in the late-wood, while Sr was more abundant in the early-wood. The differences for all three elements were always significant. The cases of consistent relationships, though rare, help to develop a research program in the area of dendrochemistry.

In dendrochemical studies, an analysis of wooden cores extracted from tree stems is a widely spread research method. A methodological problem is related to the method: whether a single core per tree can be representative of all the stems. The study aimed to estimate how the elemental contents are variable in the tree rings and whether the contents correlate among different cores. The cores were extracted from stems of Pinus sylvestris L., four cores per tree, according to the cardinal directions (east, west, north, south). The elemental contents (Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, and Sr) were estimated through the X-ray fluorescent analysis facility Itrax Multiscanner (COX Analytical Systems). The agreement between the temporal series of different cores was estimated through Spearman’s correlation coefficients. It has been found that the temporal intra-tree series for almost all the studied elements do not correlate with each other. The exclusions are Ca and K which show strong consistent correlations. The source for the correlations is, however, the long-term trends from the pith to the bark. The detrending of the Ca and K series reveals some high-frequency correlations which are not consistent among the trees. At least for Scots pine, a single core is unlikely to be a reliable representative of the whole stem in the respect of elemental content. A few research directions to overcome the uncertainty has been discussed.

The aim of this study was to find consistent correlations between weather parameters and elemental content of tree rings in four widely distributed Siberian conifers: Siberian spruce (Picea obovata Ledeb.), Scots pine (Pinus sylvestris L.), Siberian larch (Larix sibirica Ledeb.), and Siberian pine (Pinus sibirica Du Tour). Slices from the wood cores were subjected to chemical treatment by extraction in alcohol and HCl. The slices were scanned using an Itrax Multiscanner (COX Analytical Systems) to obtain the count rates of Al, P, S, K, Ca, Ti, Mn, Fe, Cu, Zn, and Sr. Every slice was scanned three times, in the original form, after alcohol extraction, and after HCl treatment. Altogether, 21 weather parameters were used to search for consistent correlations between the elemental contents. Weather parameters as well as elemental contents were averaged for successive triplets of calendar years. The statistical treatment of the data included the calculations of non-parametrical Spearman rho and Kendall tau coefficients. We defined consistent correlation as a correlation that is stronger than +/–0.3, observed in all the trees studied, and is significant at least in one tree. The main result of the study is that no consistent correlation was found that we could observe in all the species involved in the study. Nevertheless, there are several consistent correlations within the species. This means that the right choice of species for a dendrochemical study is of paramount importance. In some species, e.g., the larch and spruce, we found no correlations unless the chemical treatment was applied. Thus, a chemical treatment may reveal the reactions of tree rings’ elemental content to some weather parameters.

For dendrochemical research, it may be important to be aware of the effects of stem asymmetry and the intra-ring structure because these may introduce unwanted dispersion in the results. In dendrochemical studies, separate analysis of the elemental content of early- and latewood is rare. Also, explanations of how the elemental content may relate to stem asymmetry originating from conditions at the edges of contrasting environments are largely lacking in these studies. The purpose of the current study was to estimate the impact of the seasonal tree ring structure and stem asymmetry on the distribution of elements in tree stems. The study population was a plantation of Scots pine (Pinus sylvestris L.) at an afforestation experiment area, with the sample trees being at the edge of the stand, causing strong crown asymmetry. Six pine trees were cored through the thickness from the maximal crown side (max-side) to the minimal crown side (min-side), and the cores were subsequently scanned through an Itrax Multiscanner unit. The count rates of aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), calcium (Ca), iron (Fe), copper (Cu), zinc (Zn), and strontium (Sr) in the tree rings from 1990 to 2022 were analyzed. A group of elements (Al, Si, P, S, and Cl) tended to consistently concentrate on the min-side, both in early- and latewood, the difference being most significant for S and Cl. Regarding early- vs. latewood, Al, Si, P, S, Cl, Cu, and Zn always had lower concentration in earlywood than in latewood, while others (Ca, Fe, and Sr) had lower concentrations in latewood, the relations being consistently significant. Overall, the role of the min- or max-side of the stem in allocation of elements appears to have been weaker that the intra-ring structure (early- and latewood). Some elements such as Al, Si, P, S, Cl, and Ca (in latewood) were often more abundant on the min-side; other elements such as Fe and Sr (in latewood) were often more abundant on the max-side, but these relations were significant only on rare occasions. Intra-ring heterogeneity (in early- and latewood) appears to be more decisive than the asymmetry of the tree stem in regard to the distribution of elements in Scots pine xylem. Nevertheless, tree stems with high and obvious asymmetry should be more extensively explored because a possibility remains that extreme asymmetry does impact the allocation of elements.

In the abundant literature on plant chemistry, little attention is paid to correlations among chemical elements in tissues. The goal of the research is to establish consistent correlations among elements in the xylem of four widespread Siberian conifers. X-ray fluorescent analysis has been applied to find out the elements contained in the xylem. The method allowed finding the mean count rates of Al, P, S, K, Ca, Ti, Mn, Fe, Cu, Zn, and Sr in trunks of trees. Moreover, the xylem samples were chemically treated twice, first in alcohol and then in HCl. It was found that species factor exerts a significant influence on the elemental content of a few elements, but not on all of them. The chemical treatment decreases the impact of the species factor. The treatment increases the number of significant correlations and strength of them. In some cases (especially with Al), the correlations may change the sign of the relationship. The consistent correlations may help arrange more profound chemical research revealing the forms in which the elements exist in xylem.