Plus trees selected in natural and artificial stands is the output base for creation of clonal and seedling seed orchards. At development of the “Program of forest seed-growing development for 2010 – 2015" the realization of the extended selection of plus trees was pre-arranged on all territory of Ukraine, in particular in areas, where such trees were absent.
The aim of the presented work is to analyze the distribution of plus trees selected by URIFFM and its experimental network in 2010-2014 by exceeding in height and diameter, height of branchless part of stem depending on site conditions, natural zones.
Materials and Methods
The stem diameter at a height of 1.3 m; the height of the tree and attaching the first lower living and dead twigs; the diameter of crown; the selection category; Kraft class; the condition; origin; type of coarse bark; defects and damages; other characteristics (phenological type, availability of flowering, fruiting, etc.) were determined during the evaluation of candidate plus trees. For each tree, geographic coordinates were determined using GPS, which were entered to the passport and used for construction of schemes of trees location on territory of subcompartment using MapInfo program.
During 2010-2014, 722 candidate plus trees of pine and oak were selected. The passports are issued for all of the trees. Summarized data on the average exceeding by height, diameter and length of the branchless part of stem were grouped by natural zones and growth conditions.
The biggest exceeding of indices for Scots pine are fixed for the Polissya, and rich forest growth conditions. In poorer conditions the average exceeding is smaller. Correlation analysis revealed the influence of climatic and forest growth conditions to the exceeding indices by diameter and length of branchless part of stem. In Polissya conditions which are optimal for Scots pine growth, the selection of plus trees of I breeding category with significant exceeding is possible. In Steppe, where the southern boundary of the Scotch pine natural range is situated and natural conditions are close to critical ones, it is possible to select mainly the trees of II selection category.
For 45 Crimean pine trees the influence of medium strength of soil nutrient status to exceeding by diameter and significant impact of the soil moisture on the average exceeding of height and length of branchless part of stem (r = 0,55; 0,85, 0,91, respectively) are registered.
For 284 English oak plus trees, indices of exceeding of different natural zones are close, but in Polissya the exceeding is higher than in the Steppe, and branchless part of stem is bigger. The same as for a pine tree, the high impact of natural zone on the state and selection categories of selected trees are noted.
For Sessile oak less exceedings, both by height and by diameter, at the better debranching are registered compared to English oak.
It should be noted that the plus trees selection is only the first step in the selection process. The next steps should be the testing of selected trees by progenies and their propagation by seeds or vegetative propagation for forest seed orchards creating.
Average exceeding of selected 357 Scots pine plus trees in 12 regions of Ukraine by height were 7.5-28.9 %, by diameter 16.0-41.2 %. The decrease of exceeding and length of branchless part of stem from Polissya to Steppe are noted.
45 plus trees of Crimean pine selected in Zaporizhzhya region were characterized by average exceeding of stands indices by height from 8.6 % to 17.5 % and by diameter from 12.7 % to 42.3 %. The medium influence of the soil nutrient status on exceeding by the diameter and significant impact of the soil moisture on average exceeding by height and debranching (r = 0.55; 0.85, 0.91, respectively) are observed.
Average exceedings of 284 English oak plus trees selected in 11 regions of Ukraine by height are from 4.4 % to 27.5 %, by diameter from 13 % to 66.2%, and the average indices of branchless part of the stem are from 20.6 to 65.9 %. Exceeding by diameter increases from Polissya to Steppe, and the length of branchless part of stem, conversely, does from Step to Polissya. In Polissya the exceeding is higher than in Steppe and debranching is better. .
Selected in Crimea 36 Sessile oak plus trees characterized by medium exceeding of the average stand indices: by height from 10.6 % to 16.6 %, by diameter from 8.7 % to 19.1 % , by length of branchless part of stem from 51.0 % to 54.9 %. As compared to selected English oak plus trees, lower values of exceeding both by height and diameter at better debranching are noted.
Selection criteria for plus trees should be differentiated for different natural zones and forest tree species. Requirements to indices of diameter exceeding for Steppe hard environment conditions should be reviewed and reduced from 30 % to 15-20 % for Scots and Crimean pines.