Oak sprout dynamics after a 1996 stand-replacing fire in Korea

Abstract

Sprouting is an effective means to re-establish a forest after forest fires. However, these sprouts are vulnerable to fungi-related infection (e.g., discoloration, heart rot, and decay) through wounds on primary stumps or root systems to produce low-quality timber. A stand-replacing fire consumed 3762 ha of pine-dominated forests in Goseong-gun, Gangwon-do in 3 days in 1996 and a low-intensity fire swept the area again in 2000. We established five 9 × 9 m2 plots in the area designated for natural regeneration, where oak species (i.e., Quercus dentata Thunb., Q. mongolica Fisch. ex Ledeb, Q. serrata Thunb. ex. Murray, Q. variabilis Blume) replaced Japanese red pine (Pinus densiflora Siebold & Zucc.) forests. All the measurements were carried out in April 2010. The objectives of the study were to evaluate the natural regeneration patterns of oak species and to assess the factors associated with oak sprout discoloration. Sprout production was the highest in the third growing season from each fire in 1996 and 2000, implying that oak species might focus more on root development for the first few years and move onto sprout production. A t-test was employed to evaluate the difference between normal and discolored sprouts. There were significant differences in height, DBH, and age between normal and discolored sprouts (P < 0.05), except for those of Q. dentata. Additionally, correlation analysis was conducted between sprout discoloration occurrences and sequentially shifted annual sprout production to assess the time-lagged relationship. Discoloration occurrences showed the highest correlation coefficient with annual sprout production at a 2-year advance (r = 0.36, 0.82, 0.62, and 0.80 for Q. dentata, Q. mongolica, Q. serrata, and Q. variabilis, respectively), indicating that discoloration tended to occur within 2 years after the sprout production. Approximately 50% of sprouts were discolored showing that discoloration is a common phenomenon in oak sprouts after fire and oak sprouts would likely produce less desirable timbers. The results suggest that fire-induced oak forests should be managed for small timber forests with short rotation.