Historical logging and current successional status of old-growth Cryptomeria japonica forest on Yakushima Island

ABSTRACT

Estimation of the current successional status of long-lived coniferous forests is difficult especially after several hundred years of human disturbance. However, in Cryptomeria japonica forest on Yakushima Island, the stumps generated by logging activities from the seventeenth to nineteenth centuries remain almost intact without intense rotting. From an inventory of these stumps and long-term monitoring of current stands for more than 25 years, we estimated the forest condition before logging and evaluated the current status of secondary succession. The size structure of Cr. japonica stumps suggested the stumps were composed of two different generations: the stumps of trees present before initiation of logging; and those of trees that regenerated after initiation of logging. In the current forest, the stem number of canopy species is decreasing and that of understory broad-leaved species is increasing. Regenerating Cr. japonica individuals are rare. Before the logging, the forest contained a larger number of larger Cr. japonica trees than the current forest. The results of monitoring the current forest suggested that all coniferous species, including Cr. japonica, were still undergoing self-thinning. The current Cr. japonica forest is in an intermediate stage of secondary succession, but the processes of succession are markedly different between the study plots, depending on their location or previous logging intensity.

KEYWORDS:

• Cryptomeria japonica forest
• Long-term stand dynamics
• Secondary succession
• Stump
• Yakushima Island

Acknowledgments

The permanent plots used in this study were established by the Kumamoto Regional Forest Office. Dr Yoshisuke Inoue, Dr Yuui Sekiya, Mr Hiroo Yamamoto, and many participants maintained and managed these plots for over 30 years. We thank members of the Laboratory of Forest Management, Kyushu University, and the Laboratory of Forest Planning, Kagoshima University, for assistance with the field surveys, and Mr Kenshi Tetsuka and participants for assisting us on Yakushima Island.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The third measurements of the four plots (except KP in 1998) in this work were supported by funding for ‘Research on Conservation of Endemic Tree Species and Genetic Diversity in Ecosystems of Yakushima Island’ from the Ministry of the Environment, Government of Japan.