Wpływ typu siedliskowego lasu na wielkość i masę igieł opadających w ciągu roku w 30-letnich drzewostanach sosnowych

The article presents the size and weight of needles in 30−year−old Scots pine stands over one year with regard to the site conditions in which they grow (fresh mixed coniferous and fresh coniferous habitats). Two rectangular 1−hectare sample plots, which differed from one another only with the habitat type, were set up in Maszewo forestry in the Cybinka Forest District (western Poland). The plots were divided into 100 one−acre subplots, which were ascribed numbers from 1 to 100. In order to pick 10 plots a random number generator was used. The middle of the chosen plot became the central point of the 1−acre circular sample plots, where the measurements of all diameters at breast height and the height of every fifth tree were taken. Moreover, it was also the place where a square needle collection container (20 cm high, 1 m2 area) was located. The empty containers were placed in both experimental plots on 1st August 2017 and they were emptied on the first day of each month, throughout the entire year. The entire material was dried at the temperature of 65°C with an induced air flow. The needle mass was measured with the accuracy up to 0.001 g. Out of the samples collected each month, 300 needles were chosen at random in order to measure their length (after they were scanned with WinFOLIA program the size of each individual needle was established). Throughout the entire year, on fresh coniferous habitat the mass of the fallen needles was 2.8203 t/ha and it was by over 20% higher than it was determined for the fresh coniferous habitat. The lowest mass of the needle fall in each stand was in January, and the greatest in September on the fresh coniferous habitat, whereas in October on the fresh mixed coniferous habitat. In both of these cases, it was more than a half of the needle mass for the entire year. The average length of the fallen needles was in each month smaller on the fresh coniferous habitat and the differences between the analyzed stands were significant. The difference was the smallest (3.3%) in May, while the greatest (18.8%) in February. Moreover, significant differences in the length of the needles in the particular months in both types of stands were observed. The coefficient of variation for the needles length on the fresh mixed coniferous habitat ranged from 17.4 to 22.8%, whereas on the other habitat it varied between 14.2 and 21.6%. The mean of the coefficients of variation for the particular months was lower by 2.0% and for fresh coniferous habitat it reached 18.25%.