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Height-DBH Growth Models of Major Tree Species in Chungcheong Province.

Height-DBH Growth Models of Major Tree Species in Chungcheong Province.
Yeon Ok Seo¹, Young Jin Lee¹*, Dai Kyun Rho², Sung Ho Kim³,
Jung Kee Choi⁴ and Woo Kyun Lee
Abstract: Six commonly used non-linear growth functions were fitted to individual tree height-dbh data of eight
major tree species measured by the 5th National Forest Inventory in Chungcheong province. A total of 2,681
trees were collected from permanent sample plots across Chungcheong province. The available data for each
species were randomly splitted into two sets: the majority (90%) was used to estimate model parameters and
the remaining data (10%) were reserved to validate the models. The performance of the models was compared
and evaluated by R2, RMSE, mean difference (MD), absolute mean difference (AMD) and mean difference(MD)
for diameter classes. The combined data (100%) were used for final model fitting. The results showed that these
six sigmoidal models were able to capture the height-diameter relationships and fit the data equally well, but
produced different asymptote estimates. Sigmoidal growth models such as Chapman-Richards, Weibull functions
provided the most satisfactory height predictions. The effect of model performance on stem volume estimation
was also investigated. Tree volumes of different species were computed by the Forest Resources Evaluation and
Prediction Program using observed range of diameter and the predicted tree total height from the six models.
For trees with diameter less than 30 cm, the six height-dbh models produced very similar results for all species,
while more differentiation among the models was observed for large-sized trees.
Key words : height, dbh, growth model, national forest inventory