Net primary production is identified by means of the growth of the stand structural components and their respective increase (increment) in mass for a certain period per unit area. Environmental impact on the growth processes of forest stands and dynamics of their bioproduction processes have been analyzed in numerous studies. Taking into account a high percentage of Scots pine forests within Europe and Ukraine, the study of the qualitative and quantitative characteristics of their stands production is urgent.
The aim of the study was to estimate the total annual production of the aboveground part of the phytomass in pine stands within Ukrainian Northern Steppe.
Materials and Methods
We used the data obtained at 20 temporary sample plots (TSP) within Dnipropetrovsk Region to analyze the aboveground components of pine stands (wood and bark of stems, wood and bark of branches, needles). We assessed the aboveground phytomass fraction of trees using the method by Lakyda (2002). On the whole, 60 model trees were cut down on the TSP and measured, by fractions which enabled us to determine the current increment of stem wood. The algorithm for calculating a total annual production of Scots pine stands included a phased calculation of the phytomass production of their aboveground components, taking into account the calculation of the percentage of the current increment of the stand components and the proportion of needles per one growing year.
The results of the basic statistics showed that the variation seria of natural values of the current increment, the growing stock of stand and the wood phytomass of the stand follow a normal distribution.
The correlation analysis showed that for the current increment there was a positive correlation with all biometric indexes. The value of the current increment had a closer relationship with the growing stock of the stand; it had a medium relationship with the average height and relative density of stocking of the stand, and a weak one, with the average diameter of the stand at breast height.
We present the results of modelling and statistical estimation of the phytomass components of stem wood and bark, wood and bark of the branches, calculations of the percentage of the current increment, as well as the total annual aboveground production of the pine stands. Furthermore, we discovered that the connection of phytomass components with different impact factors can be described through the allometric regression equations with R2 from 0.22 to 0.92.
We defined that to calculate the total aboveground stand production there are three most appropriate factorial models of the dependence of the individual phytomass components on age, average diameter and relative density of stocking of the stand.
Selected allometric models were used to assess the ecological and resource potential of Scots pine stands in the State Forest Enterprises within Dnipropetrovsk Region. We have estimated that the total annual production of pine forests in the region makes 125,194.38 tons per year, where the average production of all aboveground phytomass components is 5.96 tons per hа per year.
The presented models for calculating a total annual production enable researchers to further apply them in order to evaluate the carbon sequestration and oxygen-producing functions of pine plantations in the research area.
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