Biomass production and carbon storage of Populus ×canadensis Guinier I-214 plantations grown at Pogradeci region in Albania

Fast-growing plantations of Populus ×canadensis Moench (syn. P. ×euramericana (Dode) Guinier ex Piccarolo) clone I-214 have good potential for biomass production. The objective of the study was estimation of biomass using allometric equations and estimation of carbon allocation according to tree components. The study was carried out in five poplar stands (total area 16.9 ha) in the Pogradeci region, Albania. Poplar stands were 6, 8 and 11 years old, planted at a density of 2 500–4 444 trees ha−1. We used 0.2 ha sample plots per each poplar plantation, where diameter at breast height and tree heights were measured. Sample trees in each stand were selected for determination of fresh biomass with methods of moisture content (25 sample trees) and stem analysis (five sample trees). We noted a discrepancy in dry biomass estimation between the two methods, where the moisture content method underestimated the biomass compared with the stem analysis method. Allometric equations for dry biomass were determined based on field measurements. Trees had a diameter at breast height (DBH) ranging from 2.5–24 cm and 8–21 m for height. Diameter at breast height resulted as a better allometric predictor of dry biomass than tree height. Relationships between dry biomass and predictor variables (DBH or tree height) were non-linear (exponential), whereas the relationship between dry biomass and age was linear. The squared DBH was the best predictor variable and the relationship with dry weight was fitted with a linear regression. A total of 281 t C ha−1, 137 t C ha−1, and 54 t C ha−1 was stored in 11-, 8- and 6-year-old poplar stands, respectively. Of the total C stored in all stands, 81% of carbon was allocated in the aboveground components, whereas 19% carbon was allocated in the belowground components of the trees. One-way analysis of variance (LSD test) revealed a highly significant difference in dry biomass between 6- and 11-year-old poplar stands, while the difference between 6- and 8-year-old as well as 8- and 11-year-old poplar plantations was less significant.