Influence of weather factors on seed cone formation of Siberian stone pine Pinus sibirica Du Tour (Pinaceae Lindl.)

Nowadays, when studying the fruiting of tree species, it is of great interest to understand the influence of weather factors on the inter-annual variability of fruit and seed yield. Siberian stone pine covers a large part of the Asian part of Russia and is valued primarily for its seeds. Therefore, the sustainable functioning of ecosystems depends on the yield of Siberian stone pine. Yield estimation was performed by examining bark marks from annually laid seed cones during the study period. The following categories of cone scars were recognized: (1) small triangular scar remaining from an aborted cone bud that dies before pollination; (2) triangular scar remaining from an aborted flowering seed cone soon after pollination; (3) an oval scar from a 1-yr-old conelet that developed after pollination but was aborted in the winter; (4) a large oval resinous scar from a fully mature seed cone. When studying the effect of temperature on Siberian stone pine yield, it was found that there is an increased sensitivity of initiating cone primordia to air temperature in the first decade of August. The cool weather at the beginning of August (+16 °C) contributes to the abundance of cones. On the opposite, if the temperature in the first ten-day period of August exceeds +19 °C, fewer buds are deposited. And further decrease of temperature to +16 °C in the second ten-day period of August has no effect on bud establishment.