Introduction: Forest ecosystems play an important role in the global carbon cycle. Carbon dioxide is absorbed by vegetation during the growing season and stored in plants as biomass. Trees are one of the most important and largest carbon reservoirs in natural ecosystems and are very effective in reducing atmospheric carbon emissions. Determining the amount of tree biomass is very important in the sustainable management of natural resources and also determines the contribution of forests and afforestation to the global carbon cycle. The present study attempted to investigate the amount of trunk carbon sequestration and annual volumetric growth in poplar plantations in six counties of West Azerbaijan Province.
Materials and methods: This study was conducted in six poplar-growing counties of West Azerbaijan Province, including Urmia, Miandoab, Shahindej, Naqadeh, Khoy, and Salmas, which are appropriate for wood cultivation. Poplar stands with planting density (1×2) and approximately the same age (8 to 10 years) were selected in the study areas and the quantitative variables of diameter at breast height and total height of nine trees were measured in groups in the beginning, middle and end parts (27 trees in each stand and a total of 162 trees) and the volume of a single tree was calculated in cubic meters. Then, in each county, from each stand at the time of felling, 6-disc samples from trees with a diameter of 20 cm and above were selected for testing and examination. The prepared and separated discs were cut into cubic pieces with dimensions of 3×3×3 cm. For drying, the samples were placed in an oven at 105 ° C for 24 hours and their dry weight was calculated, then the samples were placed in a furnace at 400° C and the resulting ash was reweighed. Annual volumetric growth was also obtained by accurately calculating the volume and dividing it by the number of planting years.
Results: The results indicated that the treated Populus mass in Shahindej had the highest carbon sequestration rate, with an average of 3.29 tons per hectare. In terms of growth, the stands in Urmia and Shahindej showed the highest average growth rates, at 2.84 and 2.83 cubic meters per hectare, respectively. One-Way ANOVA analysis test showed that there is a significant difference between the average amount of carbon sequestration and growth in Populus stands in different cities under investigation at the 99% confidence level. The comparison of the stands of different cities based on Tukey's test also showed that there is a significant difference between Shahindej stand and Selmas and Khoy stands at the 95% confidence level in terms of carbon sequestration. In relation to the rate of growth, a significant difference was observed at the 95% confidence level between the Populus plantations of Urmia and Shahindej couties with the Salmas, Naqdeh and Miandoab stands.
Conclusion: Due to the similar planting density, the same age of the plantations, and the relatively similar climate in the plantations investigated in the study, no significant difference was observed in terms of the amount of trunk carbon sequestration and volumetric growth in most plantations. The small significant difference observed could also be due to the management method and, to some extent, soil conditions. In this regard, it is recommended that policymakers prioritize poplar development plans by focusing on areas such as Shahindej and Urmia that have a higher potential for trunk carbon sequestration and growth increment.