Structure of aboveground phytomass of spruce and pine in short rotation plantation stands

A study of the influence of different soil and hydrological conditions of habitat on the structure of the main elements of ground phytomass – trunk, needles and branches in plantation stands of pine and spruce by the age of 40 years, grown in the Leningrad region, was studied. The results obtained showed a different level of influence of the plantation density regime during accelerated growing of pine and spruce trees on the quantitative characteristics of parts of the above-ground phytomass. There is a significant difference between these species in the considered variants of the experiment in terms of the number of trees in the plantation. Pine forms greater total aboveground phytomass in stands with a density of 1000 trees per ha than spruce. However, in the smallest and largest trunk diameter classes of pine, ground phytomass and live branch mass are lower than in spruce. The share of needle mass in spruce is higher than in pine in all thickness grades, which is due to biological peculiarities of photosynthetic apparatus of these species. It is necessary to regulate the density of pine plantations in a timely manner during accelerated cultivation and not to delay the selection for harvesting of trees of smaller thickness stages. For spruce plantations, timely selection of trees should be carried out both from small trunk diameter classes and large thickness stages, as the main trunk phytomass is deposited in the central thickness stages. For pine plantation crops, reliable differences in total ground and stem phytomass were obtained for variants with densities of 950–1050 and 1100–1200 trees per ha. No statistically significant differences were found between the other variants in the formed above-ground phytomass. The optimum possible productivity in accelerated cultivation of pine stands by the age of 40 years is observed at a density of 1200–1400 trees per ha, for spruce – 1400–1600 trees per ha.