Planted forest stands on reclaimed lands are established on a mixture of overburden grounds suitable for forests. In the dumped rocks, the humus and nitrogen contents are very low and in most cases, there is an insufficient supply of such macronutrients as potassium and phosphorus. In order to increase the fertility of the trophotope and intensify the growth of the main forest-forming species, some ameliorative plants can be introduced into the forest species composition within a stand. Among wood species, Alnus incana (L.) Moench and Alnus glutinosa (L.) Gaertn. are mostly chosen.
Materials and Methods
In a permanent trial on forest reclamation, we studied the growth characteristics of planted red oak stands from I to III age classes with the participation of grey alder as ameliorative species. The permanent trial was located within the Kozachanske Forestry, the Zvenigorodske Forest Economy. The changes in mensuration variables and the mutual influence of the tree species have been studied in pure and mixed (with grey alder) planted red oak stands during the entire period of their growth. We applied commonly used methods in forestry and normative materials to analyze the growth and development of planted red oak stands with grey alder as well as to calculate and analyze forest mensuration indicators.
At the age of 8, the average height of red oak in a mixed stand was 64 % higher compared to pure oak stand: 2.2 m against 1.4 m. The average total height increment was 46 cm against 34 cm. A 12-year-old red oak had V yield class in a pure oak stand and III yield class in a mixed one; it was Ia for grey alder. At the age of 17, in the pure stand the oak had III yield class and in a mixture with the alder Ia. At the age of 28, the yield class was I for pure oak stand and Ia for mixed one. At this age, alder had I yield class but its preservation was 9.2 % since only the best alder trees were left. The others died being not able to compete for moisture with red oak. In addition, for each variant of the trial and each species, the coefficients for the equations for the course of growth by mensuration variables of a stand have been determined. Furthermore, we defined the best age to remove grey alder from the stand due to its drying out and loss of ameliorative function.
The introduction of grey alder into the red oak plantations makes it possible to significantly improve their growth and reduce the stand development phases, namely, to shorten the period for the planted stands to become closing. The first also promotes a more rapid formation of the forest environment. The age limit till which it is possible not to cut off grey alder in red oak planted stands is 15–17 years. After that, a strong competition for moisture begins, which brings about almost complete alder mortality, as well as an increase in the red oak mortality compared to the section where the alder rows were cut. Moreover, it causes a decrease in the growth rate of the stock volume of red oak compared with the section with the cutting of alder, and even with the control.
6 Figs., 3 Tables, 15 Refs.