Site index models with density effect for hybrid aspen (Populus tremula L. × P. tremuloides Michx.) plantations in southern Finland

Models for diameter distribution and tree height in hybrid aspen plantations in southern Finland

“…The developed models were designed to be used in practice after taking the modelling data range into account. The number of trees per hectare in this study ranged from 400 to 1600, which are sparser than the prevailing practice in Finland (Hynynen et al 2002;Lee et al 2021). In addition to the compliance with these conditions, DG was evaluated as the most stable characteristic for recovering diameter distribution as presented in this study (Table 2, Fig.…”

“…experiments). The experiments were established in Lohja, Jalassaari (60°13´N, 23°56´E), Lohja, Kirkniemi (60°11´N, 23°57´E), Lapinjärvi (60°39´N, 26°08´E), and Pornainen (60°32´N, 25°20´E) in Finland, and comprised of 4-24 plots with a plot area of 1000 m 2 by location (Lee et al 2021). The experiments were repeatedly remeasured 7-12 times by site between 1997 and 2016.…”

“…The experiments were repeatedly remeasured 7-12 times by site between 1997 and 2016. The detailed information on clones, plot design, and the history of silvicultural treatment was described in Lee et al (2021). In each plot, dbh and height were measured for all trees.…”

“…Dominant height (HDOM) was calculated by averaging tree height of one hundred trees with the largest dbh per ha. Site index (SI) was computed based on the densitysensitive site index model suggested by Lee et al (2021).…”

“…Nevertheless, growth and yield models for hybrid aspen have yet to be developed for stand management purposes (Stener et al 2019). There is still a lack of modelling research except for a few studies carrying out the dominant height and site index model (Johansson 2013;Lee et al 2021), thus highlighting the importance and necessity of developing stand-and tree-level models.…”