Effect of weather cycles on cone harvesting for six coniferous species in Czech forest management

Forest tree fructification cycles play a key role in planning the production of planting material and artificial regeneration of forests, especially in the context of changing climatic conditions. Cone harvest data reflects underlying reproductive cycles, but volumes are also influenced by seed demand and forest management decisions. Nevertheless, cone harvest remains a valuable proxy in forestry, as it reflects the availability of reproductive material essential for regeneration planning and nursery production. This comprehensive study analyzes the influence of temperature, precipitation, and the North Atlantic Oscillation (NAO) on the cone collection of seed material for four native Central European (Norway spruce, Scots pine, silver fir, European larch) and two introduced (Douglas-fir and grand fir) coniferous species. The quantity of cones harvested in the entire territory of the Czech Republic in 2004–2022 ranged from 78.7 to 396.9 t·ha −1 ·yr −1 . The most intensively harvested tree species in the Czech Republic, Norway spruce ( Picea abies [L.] Karst.), shows the most pronounced 2 and 3-year cycles, with a complementary 7-year cycle, with precipitation in April and October and lower temperatures playing a crucial role. Scots pine ( Pinus sylvestris L.) dominates by 2.5 and 3.5-year cycles, influenced by precipitation in August and September and lower temperatures in September. Silver fir ( Abies alba Mill.) shows 2.3-year cycles aligned with June precipitation, while European larch ( Larix decidua Mill.) is influenced by the NAO, typically in 2-year cycles. Douglas-fir ( Pseudotsuga menziesii [Mirbel] Franco) exhibits 2.2-year cycles linked to July precipitation and NAO in June, while grand fir ( Abies grandis [Douglas ex D. Don] Lindley) exhibits 2.5-year cycles matching July precipitation. Of the forest tree species analyzed, Scots pine showed the highest correlation with the factors studied, while European larch had the lowest. The results show that tree seed crop cycles are strongly influenced by climatic fluctuations, which is essential for effective forest management. However, the 19-year dataset limits confidence in detecting longer-term cycles. Higher harvest volumes in species like Douglas-fir, grand fir and European larch are additionally affected by increased collection efforts. Understanding tree fructification cycles is crucial for planning, as climatic variations significantly affect reproductive success and the availability of planting material. Monthly variations in weather patterns notably affect the cone harvesting cycles of forest tree species.