# Growth Process and Mortality of Sasa borealis Seedlings over Six Years Following Mass Flowering and Factors Influencing Them

## TL;DR

This study tracks the growth and survival of Sasa borealis seedlings for six years after mass flowering in Japan, identifying factors that influence their regeneration.

## Contribution

The study provides the first detailed six-year analysis of Sasa borealis seedling regeneration following mass flowering.

## Key findings

- Seedling growth was slow and influenced by foraging and abiotic factors like temperature and humidity.
- Regeneration of Sasa borealis to pre-reproduction levels requires a long time.
- Biotic and abiotic factors significantly affect seedling survival and morphological development.

## Abstract

Bambusioideae, encompassing bamboo and dwarf bamboo, is a subfamily of clonal plants reproducing through rhizome-type nutritional reproduction. The duration of nutritional reproduction varies from three years to more than 120 years, depending on the species. This process is characterized by synchronous sexual reproduction among individuals within a region, followed by mortality after sexual reproduction. From 2016 to 2017, Sasa borealis exhibited sexual reproduction (mass flowering and mast seeding) in northeastern Aichi Prefecture, central Japan. This is a dwarf bamboo species that grows on forest floors. We investigated the regeneration process of S. borealis from seed dispersal to germination and the growth of seedlings while considering biotic and abiotic factors. This study clarified the timing of seedling emergence and the factors influencing their number. We observed that the growth and morphological characteristics changed because of differences in the forest floor environment and foraging on parts of the seedlings. The findings regarding regeneration following sexual reproduction in this study provide the first step toward quantifying the regeneration process and timeline for environmental recovery after severe disturbances to forest ecosystems.

The sexual reproduction of Sasa borealis, a species of dwarf bamboo, occurred in central Japan from 2016 to 2017. S. borealis grows on the forest floor and serves as an important source of habitat and food for various animals. Sexual reproduction occurs in synchrony among individuals in a given area, leading to a decline in population and causing substantial disturbances to the forest ecosystem; however, the subsequent regeneration process remains unclear. In this study, we investigated S. borealis seedling regeneration over six years. Fixed plots were established in the forest in the year following the sexual reproductive event, and the growth of seedlings was monitored from seed emergence to seedling growth at the individual level. We considered biotic and abiotic factors to evaluate their influence on regeneration. We examined mammalian and arthropod foraging as biotic factors. Conversely, abiotic factors included temperature and humidity near the ground surface, solar radiation, soil conditions, and snow cover. Seedling growth was characterized by a slow rate and affected by morphological changes resulting from foraging and abiotic factors. The return of S. borealis to its presexual reproductive stage requires an extended duration. Our study provides precious information for future S. borealis conservation and management strategies.