Modeling the Phytomass of Dead Branches in Standing Trees of Pinus Sylvestris L
Introduction. In a changing climate, estimates of the total carbon pool of all components of forest ecosystems, including the mass of dead branches (DBM) of standing trees, are increasingly relevant. According to published data on the tree phytomass, the ratio of DBM to the aboveground phytomass, or relative DBM (RDBM), ranges from 0.3 to 29 %. However, attempts to identify the factors explaining such a wide range have been quite rare. The aim of the study. In this research, the first attempt was made to develop allometric models for estimating DBM and RDBM of Pinus sylvestris L. trees growing in the natural forest stands and plantations of the steppe and forest-steppe zones. Objects and methods. The object of the study was pure island pine forests of natural and artificial origin located in the steppe area of the Turgay Depression. For comparative purposes, published data on natural Pinus sylvestris L. forests of the Krasnoyarsk and Kansk forest steppe were utilized; their comparative evaluation in regard to DBM and RDBM was carried out. In total, 595 model trees taken from 48 sample plots were used for the analysis. Results. The analysis of paired associations of DBM with dendrometric tree characteristics showed that the trunk diameter at breast height (DBH) accounts for 87-92 % of DBM variability, and the tree height accounts for 81- 88 % of it. With an increase in DBH from 6 to 26 cm, RDBM in the Turgay steppe plantations rises from 6 to 13 %, while in natural pines forests it remains stable at 4 %. A comparative analysis of DBM of trees in plantations and natural forest stands, which was performed using a two-factor model depending on DBH and the tree height, showed that DBM in plantations was 1.8 times higher than that in natural stands. A comparative analysis of DBM of trees in the natural pine forests of the Turgay steppe and the Krasnoyarsk and Kansk forest-steppe revealed little difference; on average, with an increase in DBH from 6 to 26 cm, DBM changes from 0.3 to 9 kg, while RDBM remains stable at 4 %. With increasing age and constant DBH, RDBM in the natural pine forests of the two regions decreases from 10-19 % to 2-4 %. Conclusion. When calculating the carbon pools of the aboveground phytomass, it is necessary to make a correction to the pool estimate as a 6-13% increase for the steppe zone pine plantations, and as an increase of 4 % for the natural pine forests of the steppe and forest-steppe zones.