Slope angle determines the productivity of edible culms of Sasa kurilensis in a northern Japanese forest

ABSTRACT

Despite their potential usefulness as a natural resource, wild edible bamboos tend to be ignored or neglected by foresters, and we know little about how environmental factors determine the productivity of edible culms. Here, to examine determinants for the productivity of edible culms of Sasa kurilensis, 60 survey plots were established in a northern Japanese forest, and annual field surveys were carried out over 3 years. The results show that the density and stem diameter of edible culms were determined by the local density and stem diameter, respectively, of old culms. This indicates that we can predict how many and what kind (thickness) of edible culms will be produced based on information about the demographic properties of old culms. Then, by using the GIS-linked data, the environmental factors that affect the demographic properties of old culms were explored. As a result, slope angle was the most influential environmental factor; that is, the density of old culms decreased but the stem diameter increased along the gradient of increasing slope angle. This indicates that the productivity of valuable culms in flat areas may be low since edible culms with small stem diameter are less valuable for eating. To confirm this, the productivity of valuable edible culms, which have a basal diameter larger than a specified thickness was estimated at each site, and a hump-shaped relationship between productivity of valuable edible culms and degree of slope angle shows that the productivity of valuable edible culms can be maximized at medium slope angle.

KEYWORDS:

• Bamboo
• ecosystem services
• GIS
• non-timber forest products
• wild edible plants

Acknowledgments

I especially want to thank Drs. Osamu Kishida and Kentaro Takagi and the staff at the Teshio Experimental Forest of Hokkaido University for their great support of our experiments during this study. I am also grateful to Mr. Shintaro Hayakashi for his helpful comments on GIS analyses for this study.

Disclosure statement

There are no potential conflicts of interest.

Geolocation information

The study site was located in the Teshio Experimental Forest of Hokkaido University (45°03ʹN, 142°07ʹE).

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by Grants-in-Aid for Scientific Research of Japan Society for the Promotion of Science (JSPS) Noboru Katayama [grant numbers 26740045 and 18K11724].