The basic density stems of the main wood species in the forest stands within northern steppe of Ukraine
Authors: Sytnyk S. A. , Lovynska V. M. , Maslikova K. P. 
Published: February 2018

The goal of this research is determination the values average basic wood’s density in the bark of Pinus silvestrys (Scots pine) and Robinia pseudoacacia (black locust). It is established the depending of searching parameter from the main biometric characteristics of trees such as age, diameter of the trunk on the height 1.3 m (d1,3) and height (h) of the trees. The experimental data to determine basic wood density obtained on the thirty temporary plots (sample), where were felled thirty model trees and carried out their evaluation by the fraction. The basic wood’s density in the bark was analyzed according to the main biometric indexes the model trees: age, diameter and height of tree. For the studied species, both for Scots pine, and black locust noted the gradual increase the average basic wood’s density in the bark with growing age of the trees. Thus, for Scots pine fixed the minimum value (245 kg·(m3)-1) of basic wood’s density for the sample in the youngest age, and then recorded the temperate increase this parameter. The maximum value fixed for the oldest sample  (90 years). By analyzing of the change average basic wood density in the bark of black locust found that the maximum value of this index (605 kg·(m3)-1) was recorded for trees in the age 84 years that belonging to the overmature age group, while the minimum value (438 kg·(m3)-1) have the trees in the age 30 years. The distinctions in the value of the average basic density are 27.6%. More high value of basic wood’s density in the bark have the black locust sample compared with Scots pine. The percentage difference between the maximum value of both investigated species is 22.5%. The average basic wood’s density is characterized by increasing type with the age. It was observed both for Scots pine, and black locust. The established dependence of changes of wood basic density of black locust can be related with the proportionate changes in parenchyme tissue and structural elements of xylem vessels. The value of the average basic wood’s density increases with growing diameter at breast height and reaching the maximum values 439–469 kg·(m3)-1) in the Scots pine sample with diameters from 24.3 to 26.1 cm, and then decline. The absolute value of the average basic wood density in the bark is characterized by the significant variation relative to the trend line. The average basic wood’s density in the bark depending on the height tree. The highest index (469 kg·(м3)-1) established for the sample with a height of 22.3 m. Within these altitudes are concentrated the highest values ​​of the studied parameter. Analyzing the data in another study species (black locust) it should be noted that the basic wood’s density in the bark is the constant value. There is observed a few variation of the values ​​of basic wood’s density in bark relative trend line. This fact can be explained by the different age of the sample of Robinia pseudoacacia and its impact on the basic wood’s density in the bark. Thus, this index gradually increases with the aged trees and with the increase diameter and height and then decreases for trees with a maximum diameter (27.4 and 28.6 cm) and height (21.6 and 22 7 m). The maximum value the basic wood’s dencity in the bark (605 kg·(m3)-1) fixed for the sample black locust with a height 24 m and the diameter 15.7 cm. The results of correlation analysis shown the close correlation between the value average wood’s density in the bark both for black locust, and Scots pine with a diameter 1.3 m and height of trees. All correlation coefficients of basic wood’s density in the bark for both studied species with the diameter and height of trees, or else the density of these indexes have a direct relationship. Closely (r = +0,61+0,62) correlation found for basic wood’s density in the bark for Scots pine with height trees, while for black locust the closely correlation  found with both studied biometric parameters as for diameter and height. The average wood’s density in the bark of Scots pine is a few weak (r = +0,55), but significant correlation with stem diameter. Overall, the studied parameters change with the diameter and height of the trunk and depend on the age of the tree. Identified laws allow to establish of the mathematic depends for assessing components of biomass stem. It is necessary to study the biological productivity of forests.