Home – Home – Jornals – Siberian Journal of Forest Science 2022 number 3

The capsule review of the scientific editor for the thematic issue of the Siberian Journal of Forest Science, 2022, number 3 is done, dedicated to silvicultural problems in Siberia.

As a result of an experiment on thinning of different intensity and the application of fertilizers (carbamide, 46 % as the active ingredient) in the young stands of the Krasnoyarsk forest-steppe, formed on former agricultural land, with the initial density 30 thousand trees per ha, data were obtained on the response of cenoses to the complex treatment. Dependences of growth on the age and initial density of plantings, and on the density and dose of fertilizer were built. It is shown that on the plots with the thinning intensity of 77 and 59 % of the number of trees, after 10 years it is necessary to carry out a second thinning treatment. It has been established that the growth response to the application of fertilizers begins from the fifth year after their application. The application of fertilizers makes it possible to reduce the competition between trees for environmental resources, which allows overdense young stands to provide the maximum possible productivity up to a certain age. The results obtained can be used not only in solving forestry problems of increasing the productivity of plantations, but also to increase their carbon sequestration functions.

Based on the analysis of the wood increment dynamics in the middle-aged pine forests of the Krasnoyarsk forest-steppe of various structure, formed through thinning of different intensities and the introduction of various doses of mineral fertilizers (carbamide, 46 % of the active substance), the regularities of changes in the current annual increment were established. A model allowing assessing the trends in increment with age and density of stands growing both without and with the use of fertilizers has been proposed. Data are presented indicating that in the conditions of the Krasnoyarsk forest-steppe, due to the application of fertilizers, the current annual increment in pine plantations can be increased by 1.2-6.8 m³/ha compared to the reference site. Differences in the response of stands to fertilization in the first five years and the next three years were revealed it has been found that the current annual increment increases significantly starting from the sixth year after fertilization. The density-age optima of the productivity of pine stands, providing a multiple increase in the increment of managed stands as compared to the reference site were established. The obtained knowledge is the theoretical basis for the implementation of a model of intensive use and reproduction of forests in the best forest growing conditions, and will also be useful in creating carbon farms, which main purpose is to reduce the carbon footprint of industrial enterprises.

The dynamics of forest inventory indicators, attrition and wood growth of 35-year-old pine Рinus sylvestris L. crops with various density are analyzed, Pine crops were created in 1982 by V. N. Sukachev Institute of Forest Russian Academy of Sciences, Siberian Branch under the leadership of A. I. Buzykin on former agricultural lands in Bolshemurtinsky district of Krasnoyarsk Krai. The initial density of the stands varied in a wide range from 0.5 to 128.0 thousand trees per ha. The assessment of the stand density influence on the growth and productivity of young pine stands at the age of 2, 5, 12, 15, 20, 25, 30 and 35 years old was carried out. It has been established that since the age of five, the process of intensive self-thinning of trees has been observed, at initial planting density 90.0 thousand trees/ha the density decreased to 10 thousand trees/ha by the age of 35 years. At the initial density less than 10 thousand trees/ha the self-thinning intensity is significantly lower and the stand density has decreased by less than 2 times over the same period. It is shown that at the initial stage of stand growth there is a growth increase with the initial planting density, reaching the plateau at a density of over 70.0 thousand trees/ha. With age reaching the plateau occurs with the lower initial density. At the age of 20, the maximum increase was at the initial density from 50.0 to 70.0 thousand trees/ha, by the age of 30 it shifted to a density range from 30.0 to 50.0 thousand trees/ha. The relationship between the current annual increment, age, and the initial and actual densities of pine crops has been established. In the age range studied there is a tendency of increasing the increment with age, although for the crops with the initial density higher than 90 thousand trees per ha in the range of 15 to 22 years the decrease of annual increment is observed, which is evidently connected to the escalating of concurrent relations in cenosis. Thus, it can be suggested that high rates of carbon deposition at the initial stage of high-density stands creation can be maintained under the condition of periodic thinning, regulating the stand density.

The results of the formation of overstocked 15-year pine stands (with initial density of trees 35.6 thousand per ha) in the Krasnoyarsk forest-steppe the thinning aimed at reducing their density with keeping only the trees of a certain cenotic position (dominant, co-dominant and suppressed) in order to obtain information about the possible equalization of their forest inventory indicators in the process of their growth are presented. It was found that after thinning the dominant trees stand had density of 4.3 thousand per ha, had the best growth characteristics (mean height and mean diameter) and upheld that tendency through the whole observation period. After 7 years mean diameter of dominant trees increased from 4.8 ± 0.1 to 9.4 ± 0.2 cm, mean height increased from 4.8 ± 0.1 до 8.1 ± 0.1 m. Stem timber volume increased 5.0 times to the value of 141.63 m³ per ha, relative density - from 0.51 to 1.27. Stand density for co-dominant trees decreased to 6.6 thousand per ha after the thinning. The mean diameter of co-dominant trees increased 2.6 times and amounted 6.1 ± 0.1 cm, the mean height increased from 3.4 ± 0.1 to 5.7 ± 0.1 m. Stem timber volume increased from 7.92 to 60.06 m³/ha, relative density increased 3.7 times (1.00). After the thinning the suppressed trees underwent a long (1-2 years) adaptation period, had disproportional growth in height and decreased growth in diameter (relative height 244). Stand density for suppressed trees pine Pinus sylvestris L. decreased to 6.3 thousand per ha after the thinning. The mean diameter of the suppressed trees after 7 years after the thinning changed from 0.9 ± 0.1 to 4.2 ± 0.1 cm, the mean height - from 2.3 ± 0.1 to 3.8 ± 0.1 m. Timber volume increased from 1.09 to 17.23 m³ per ha, relative density increased from 0.07 to 0.69.

A simulation model of the growth of pine stands is proposed. The model, taking into account the competition for the available resource, allows to calculate the increase in trunk diameter for each tree in the simulated area, as well as to derive the taxation characteristics: stand density, completeness, stock of stem wood and make monitoring the dynamics of all these indicators in increments of one year. The model takes into account the relative location of trees in the tree stand, their size and the amount of available resource for each tree. The verification of the model was carried out using the materials of long-term research on permanent research plots of young, middle-aged and ripe stands. Several scenarios for the growing of pine stands are considered. The influence of cutting on the dynamics of a number of taxation characteristics is studied. These are the average diameter the average diameter of the trunk and the increase in diameter, the value of the average annual increase; the density of the stand; the stock of stem wood. The proposed simulation model is an effective tool for studying the growing of stands and serves as an alternative to time-consuming field studies, which are difficult to implement over long time intervals. Modeling allows studying the impact of logging in forests for various destinations. It is possible to choose such a system of forest care activities using the analysis of the dynamics of the main taxation indicators, which provides the most complete implementation of the tasks of intensive reforestation by varying the intensity and frequency of cutting during modeling.

The basis for forecasting the growth of forest stands is the site index scales. Expansion of knowledge about the processes of functioning of forest ecosystems, the nature of changes in the process of growth of morphological indicators of trees and stands, their interconnections and interdependencies, and the creation of a more suitable mathematical apparatus and appropriate software for describing biological processes form the prerequisites for formulating and solving the problem of forecasting the growth of stands on higher methodological level. The aim of this work is to assess the predictive ability of the growth equations obtained using the generalized algebraic difference approach (GADA) to describe the course of growth of tree stands at the average height and to construct a site index scale. The data for the study were general tables of the course of growth of complete (normal) pine stands North Eurasian. A total of 25 equations obtained using the GADA approach are analyzed. Comparative analysis showed that the best quality of data alignment is provided by an equation based on the Mitscherlich function (also known as Drakin-Vuevsky, Chapman-Richards) with the replacement of parameters responsible for the limiting values of the height and the shape of the curve. This model is polymorphic, has the shape of a sigmoid curve and variable asymptotes, i.e. takes into account most of the properties imposed on the growth rate models in height. Model errors are distributed depending on the selected forecasting interval and the site index of the stand. With an increase in the forecasting period, an increase in the error occurs. For all intervals of the forecast range, the value of the mean absolute error is not exceeding 2.01 %. The highest average absolute forecast error (1.1-2.2 %) is characteristic of the extreme site index classes (I^b, V, V^a and V^b). The methodology considered in the study can be applied to develop models of the growth rate of stand inventory variables of other forest-forming species in Russia.

Qualimetry of aboveground and underground biomass of trees is an integral part of studies of biological productivity and carbon depositing capacity of forest cover, necessary for the correct assessment of the carbon cycle in its spatial gradients and in relation to climate change. The great bulk of carbon is deposited in tree stems and largely depends on the basic density (BD) of wood and bark. The author’s database on the qualimetry of forest-forming species of Northern Eurasia is used in the work. About 3.450 model trees of 9 tree species (genera) were selected from it. The constructed mixed-effects models describing the dependences of the BD of wood and bark on their dendrometric indicators, geographical coordinates and species belonging of trees, revealed a 0.25% decrease in the BD of wood by 1 ° N. in the direction from south to north and 0.26 % decrease by 1 °E. in the direction from west to east. In the same gradients, the decrease in the BD of the stem bark is 0.55 % by 1 °N. and 0.28 % by 1 °E., respectively. The largest share of the explained variability of BD is accounted for by the species of trees - 74 % for wood and 87 % for bark, significantly less - by geographical location - 12 and 9 %, respectively, and the smallest share - by dendrometric indicators of trees 14 and 4 %, respectively. The ranking of species of equal-sized trees by BD value was performed, which showed that each species has a specific ratio of BD of wood and bark. This means that for a more correct assessment of the basic density and carbon deposition in wood and bark, it is necessary to process separately wood and bark of the disks removed from stems, and not the disks over bark as a whole.