Potential for soil seed banks to drive vegetation changes in windswept Sasa grasslands in eastern Japan

ABSTRACT

Windswept Sasa grasslands are stable communities but may have the potential to change into other vegetation such as forests through germination of the soil seed bank. I investigated the compositions of the vegetation and soil seed banks in two windswept Sasa grasslands in the Tanzawa Mountains, eastern Japan: Ryugababa (RGB) and Fudonomine (FDM). Tall tree and sub-tall tree seedlings were present in both grasslands but were below a dense cover of Sasa hayatae. The number of buried viable seeds was estimated as 2831 seeds m⁻² comprising 39 species at RGB and 5786 seeds m⁻² comprising 58 species at FDM, 70% of which were graminoids and 5−23% of which were sub-tall trees at both sites. Most sub-tall tree seeds were Weigela decora, which forms windswept scrub forests around Sasa grasslands. No seedlings of S. hayatae germinated from any of the soil seed bank samples. A habitat type analysis of the soil seed banks showed that the “other” type (species that are infrequent or do not belong to a particular plant association) had the highest relative dominance (approximately 70%), followed by windswept scrub forest (13−25%) at both sites. Sørensen’s similarity index between the vegetation and soil seed bank was low (39.6% in RGB and 47.1% in FDM), possibly because the dense Sasa cover prevents seedlings from germinating and growing. These results suggest that the soil seed banks in windswept Sasa grasslands have different species compositions from the vegetation and consequently have the potential to cause a shift to W. decora scrub forest.

KEYWORDS:

• Graminoid
• Scrub forest
• Sørensen’s similarity index
• Sub-tall tree
• Vegetation

Acknowledgments

I thank H Nemoto and H Kamimura for their help with soil sampling; H Nakayama, Y Nobe, and S Hatazawa for help with the seedling emergence survey; and A Shoji of the Ryokusei Research Institute Inc. for help with vegetation surveys during my study.

Disclosure statement

I have no potential conflict of interest.

Geolocation information

The study was conducted in the grassland and forested landscape of the Tanzawa Mountains (35°28ʹ08.0”-35°28ʹ42.6”N, 139°09ʹ22.2”- 139°09ʹ53.1”E).

Supplementary material

Supplemental data for this article can be accessed here