Rhizome extension characteristics, structure and carbon storage relationships with culms in a 10-year moso bamboo reforestation period

Abstract

Moso bamboo (Phyllostachys pubescens) forest plays an irreplaceable and significant effect on carbon sequestration and the adaptation of forestry to climate change in South China because of its high growth rate and adaptability to adverse environmental conditions. There may be a relationship between rhizomes and ramets because moso bamboo, as a monopodial running bamboo, grows belowground by rhizome branching and elongation and spreads ramets aboveground. This study used terrestrial laser scanning (TLS) to accurately quantify the above- and belowground structure and dynamics of moso bamboo forests after reforestation, indicating that the number and carbon storage of rhizomes exhibited significant “on-year” and “off-year” features and in even-numbered years were significantly higher than those in odd-numbered years. No significant variation was found in the average diameter of the rhizome (DR), while the average diameter at breast height (DBH) increased significantly from the 3rd year, and the three greatest increases in DBH occurred after the year in which rapid rhizome growth occurred. The depth of the rhizomes ranged from 3.54 to 38.47 cm, and the rhizomes were mainly distributed in the 10–30 cm soil layer. The angles of the rhizome and subrhizome (ARSR) were mainly less than 30°and increased over time. Rhizomes store and allocate nutrients by increasing the length and number of rhizome segments (NRS) and normally maintain connections over tens of metres. Both the number and biomass of culms were significantly positively correlated with the total NRS, total length of rhizomes, number of rhizomes and rhizome biomass under different rhizome-culm systems. We used a linear equation (y=4.112x+9.337,R2=0.7605,RMSE=19.36) to accurately estimate the rhizome biomass based on the aboveground biomass and the ratio of aboveground and rhizome carbon storage (RCS) to accurately estimate RCS in different years after reforestation.