The main purpose of seed orchards is to obtain regularly seeds of the highest genetic value for forest plantations. Long-term research in Ukraine and foreign experience show that there is a significant reduction in the cone yield on orchards that are over 26–28 years old even with free spacing of ramets. The aim of the study was to identify peculiarities in reproduction of Scots pine on Clonal Seed Orchards (CSO), based on comparison for performances of flowering intensity and seed production from different clones, their groups and CSO in Rivne region. The object of the study is the clonal seed orchards of Scots pine (Pinus sylvestris L.). The subject of research is the reproduction of clones on clonal seed orchards of Scots pine. The intensity of «flowering» and seeding of clones on CSO was determined by continuous list of each ramet. To assess the intensity of female «flowering», we determined the growth and the reproductive layer of the crown, the rank position of pine clones on plantations, which we divided into three groups: high, medium and weak. We analyzed the intensity of growth, «flowering» and seed production of Scots pine clones (Pinus silvestris L.) for many years on the plantations of 1977 and 1984. At CSP of 1977, the «flowering» within clones is characterized by a mixed-sexual type; on the plantation of 1984, the most clones (54.2%) were dominated by female «flowering». The rate of microstrobiles formation in clones on the younger plantation (CSP-1984) is lower than the intensity of megastrobiles formation by 4.0%, while on the older one (1977), on the contrary, the intensity of microstrobiles formation was dominant by 118.2%. The average yield of strobiles from the number of megastrobiles on the CSP of 1977 and 1984 was 70.1 and 74.3%, respectively. The close correlations were found between the number of megastrobiles and the number of strobiles (r = 0.94 and 0.84). The variation in the number of strobiles per tree over the years of observation is quite high and varied in clones of 1977 from 40.2% in 2004 to 70.7 in 2003 and averaged 52.6%; clones of 1984 ranged from 43.6% in 2004 to 78.8% in 2005 and averaged 59.3%. The number of female strobiles for the six-year period at CSP of 1977 averaged 45.8% from the number of male ones; for three years — 4.0% in clones of 1984. Their number ranged from 25.5 to 61.3% in clones of 1977; in clones of 1984 – from 16.5 to 77.5%. Depending on the clone and the weather conditions of the growing season, the ratio between the number of female and male strobiles within each clone is from 29.8 to 166.7% on CSP of 1977 and from 49.4 to 1005.4% of 1984. The correlation between the number of mega- and microstrobiles on CSP of 1977 is weak (r = 0.17), and the ones of 1984 – high (r = 0.77). No dependences were found between the preservation of megastrobiles by their number (abundance of «flowering») in clones of 1984 and the average correlation (r = 0.33) was found in clones of 1977. According to long-term data on CSP of 1977, the most productive is clone No 22. The highest yield of strobiles from the number of megastrobiles on the plantation of 1984 – in clone No 130 (88.1%), the lowest — No 121 (46.7%). Only two clones (No 22 and 97) and eight clones of 1984 (No 116, 118, 127, 129, 130, 137, 138, 139) are included into the group of clones of 1977 with abundant «flowering», harvest and high yield of strobiles). The clones that have the high and medium growth intensity, with high and medium flowering intensity, with high and medium yield of strobiles are perspective for seed plantations among the selected groups.
Cone and seeds variability in seed orchards and seed stands of Pinus sylvestris L.