Changes in Tree height–diameter allometry for temperate forests: A large periodical observational study

Forest biomass is used as a representative factor for forest size, forest maturity, and forest productivity, so quantitative evaluation is very important not only for management and harvest but also for the evaluation of ecosystem functions and services including CO₂ absorption. The allometric equation is a method of estimating the value of each part through the relative growth rate of plants and is a methodology widely used from the past to the present. Recently, studies have shown that the relative growth system of trees is changing due to the increase in CO₂ concentration in the atmosphere and the resulting climate change, raising the need to review the previously developed relative growth and coefficients. In this study, the height-DBH relative growth relationships of four major tree species in Korea [(Pinus densiflora (PD), Larix kaempferi (LK), Quercus variabilis (QV), and Quercus mongolica (QM)] were analyzed using the 5―7th NFI data. Furthermore, these results were compared with the present yield table from the national institute for forest science. As a result of the analysis, it was found that the expected height value for the same DBH increased as the NFI progresses. For example, as a result of model analysis, the expected height for PD, LK, QV, and QM for DBH 25cm were 12.48, 19.17, 14.47, and 13.19m in the 5th NFI data, respectively. From the 7th NFI data, they were estimated as 13.61 (+9.1%), 21.58 (+12.7%), 15.76 (+8.9%), and 13.93 m (+5.6%), respectively. These results indicate that the current growth of major tree species in South Korean forests is more active in height growth than in diameter growth under climate change when compared with the height-DBH development trends by tree species identified through past survey data.