Species heights of Siberian spruce on the Yenisei Ridge

. The work is based on materials from 15 sample plots laid out in mixed spruce stands of the Yenisei Ridge, with a relative completeness in the range of 1.62-1.27, belonging to the green moss group of forest types. Based on the data obtained, the features of changes in spruce species heights and their interdependence with other taxation characteristics were established. The results of data processing indicate the need to develop a set of taxation standards for the Yenisei Ridge region.


Introduction
Species height, that is, the product of height by species number (Hf), is one of the most commonly used indicators in determining the volume of tree trunks and forest stands.This indicator is widely used in the development and preparation of taxation standards, such as volumetric and assortment tables.The table of species heights as an independent standard entered into taxation practice in 1969 as part of the "Manual on the allocation and taxation of cutting areas in the forests of the USSR."This standard was built on the basis of data from regional volume and assortment tables used in the practical activities of forestry enterprises.Of course, one table could not cover the entire diversity of forest conditions reflected in the formation of tree trunks.
The established patterns in changes in species heights allowed N.V. Tretyakov and N.P. Anuchin to obtain a number of empirical formulas for determining forest stocks.
It turned out that the nature of changes in species heights and their average values largely depend not only on the tree species, but also on the characteristics of forest growth conditions that determine the process of formation of a particular forest plant system.
A relatively small number of works are devoted to the peculiarities of the formation of series of species heights of tree species in Central Siberia [1,2,4,6]).It should be noted that the study area -the Yenisei Ridge -has quite specific climatic and soil conditions that distinguish it from other regions of Central Siberia.This mountain system in the southwestern part of the Central Siberian Plateau is characterized by a sharply continental, harsh climate, caused by difficult access to humid air flows from the Atlantic Ocean.
Soil formation processes in the region are mediated by permafrost phenomena.Dark coniferous forest stands with a predominance of Siberian fir (Abies sibirica Zedeb.) and Siberian spruce (Picea obovata Zedeb.) with the participation of Siberian pine (Pinus sibirica Du Tour.) are characteristic of the southern part of the Yenisei Ridge.
The purpose of this work was to establish the features of the formation of species heights of spruce stands in the conditions of the Yenisei Ridge mountain range.

Materials and methods
The work is based on materials from 15 trial plots, where 159 model trees were cut down and measured.The establishment of trial plots was carried out in accordance with the requirements of OST-56-69-83 "Trial forest management plots.Bookmark methods." The characteristics of the trial plots are given in Table 1.All tree stands of the trial plots belong to the green moss group of forest types.In absolute predominance they are highly dense, with tree stands on three sample plots -5; 11 and 13 have a relative completeness higher than standard.For model trees, heights, diameters in bark and without bark were measured at a height of 1.3 m, root collar, 0.25; 0.50; 0.75 trunk height.The volume was determined according to Huber's complex formula, for which the trunks were divided into two-meter sections.The output of assortments was established.Frequent root rots made it difficult to accurately determine the age of trees.

Results and discussion
The series of species heights obtained from the data of model trees, in which the volumes were found in the bark and without the bark, were processed statistically.As a result, almost identical results were obtained: for trunks in the bark, the average Hf value was 8.8 ± 0.2; with a coefficient of variation of 27.8% and experimental accuracy of 2.2%; for trunks without bark, respectively, 8.7 ± 0.2; 24.4%; 2.2%.This indicates that the bark of Siberian spruce is evenly distributed along the trunk and, unlike species such as larch and pine [2,3], does not in any way affect the full woodiness of the trunks.
Correlation analysis showed a high degree of dependence between species height and the main taxation characteristics of model trees.The magnitude of the correlation coefficients between Hf and the delay is 0.92; Hf and D1.3 -0.85; Нf and V -0.81.To establish the characteristics of changes in species heights in the spruce forests of the Yenisei Ridge, linear equations were found that reflect changes in this indicator in trees included in individual fourcentimeter thickness steps (Figure 1).The coefficients of the equations and their adequacy indicators are given in Table 2. Analysis of the set of equations showed that, despite the fact that some of them can be considered only at the level of trend (thickness levels 40; 48) due to the small number of observations or the large variability of the trait.In general, the graphs formed a single field with no breaks or significant deviations.
This distinguishes shade-tolerant dark-coniferous spruce forests, in which renewal processes occur almost constantly, which determines the presence of trees of different ages and sizes, from forest stands formed by light-loving species [5].
So, according to N.N.Kulakova [2] in the larch forests of the Lower Angara region, similar graphs are formed by two zeros.The first includes rows of specific heights of trunks, included in thickness steps of 8-44 cm, where the lines have a clear orientation and complement each other.The second field is formed by the largest part of the forest stand (thickness steps of 48-56 cm), where the graph lines have a significant scatter and differ from each other in the angle of inclination to the height axis.The author explains this by the fact that, on the one hand, trees with a significant diameter have an age at which the processes of growth in height are already fading away, and the increase in diameter continues, and on the other hand, by the fact that in light-loving species, large-sized trees are formed in relatively open spaces (edges) glades) in less competition for light and living space, which certainly affects the shape of the trunks.Similar data are provided by M.N.Efremova [1] for birch stands of island forest-steppes in Central Siberia.
Next, for the entire set of data, an equation of the form was obtained: The adequacy of the equation corresponds to the coefficient of determination (R2) of 0.864.
The dependence is illustrated by the graph in Figure 2.This equation was a mathematical model of the table of view heights for the object of study (Table 3).A comparison of the obtained data with current standards is illustrated by the graph in Figure 3.The graph shows the change in species heights in accordance with current standards (Hf table), the change in species heights according to model trees (Hf) and the average species heights for trial plots (Hf samples).
Figure 3 shows that the indicators are close only within the average heights of 10-16 m.With increasing height, the differences increase, reaching 16.8% at a height of 30 m. Undoubtedly.these differences entail an error in determining the stocks of Siberian spruce stands in the study area.especially when estimating cutting areas using the method of relascopic circular sites.

Conclusion
The harsh mountain conditions of the Yenisei Ridge determine the specific growth regime of woody vegetation.In the region, mainly forest stands are formed, characterized by relatively low productivity.One of the factors influencing the stock of forest stands is the shape of the trunks, reflected by the "species height" indicator.
As a result of the work, in which an analysis of the species heights of Siberian spruce was carried out, it was found that they are significantly lower than the values of this indicator used in the current standards, which causes significant positive errors in determining forest stands.To eliminate them, it is necessary to adjust the taxation regulatory framework for the study area.
The bark of Siberian spruce does not have a significant effect on the shape of spruce trunks.

Fig. 1 .
Fig.1.Relationship between species heights and tree heights within thickness levels.

Fig. 2 .
Fig. 2. Relationship between height and species height in spruce stands.

Fig. 3 .
Fig. 3. Comparison of the obtained data with the data of the current standard.

Table 1 .
Characteristics of tree stands on trial plots.

Table 2 .
Equation coefficients and adequacy indicators.