Assessing belowground carbon storage after converting a temperate permanent grassland into a bamboo (Phyllostachys) plantation

Bamboo (Phyllostachys sp.) is considered a sustainable resource that can replace fossil fuel‐based products. Its additional ability to sequester organic carbon in the soil (SOC) makes it a promising nature‐based solution for combating climate change. However, bamboo's soil C storage potential may vary considerably between species or growing conditions and needs to be better quantified, especially in temperate climates where data are lacking. In the present research, the SOC dynamics of plots converted from grassland to plantations of three bamboo species (i.e. Phyllostachys nigra, Phyllostachys aurea and Phyllostachys aureosulcata), planted 12 years ago on podzol (World Reference Base classification) in the Belgian Campine region, have been studied. Soil and root samples were taken until a depth of 40 cm using a 10 cm interval. Besides, the total belowground C stability (mgCO2‐C g−1 C h−1) was assessed by measuring during 3 months the carbon dioxide (CO2) efflux relative to the belowground C stock. Based on an equivalent soil mass, only P. aureosulcata, the species with the highest culm basal area, had a significant (p < .001) SOC increase of 5.0 kg C m−2 (relative increase of +94%) as compared with grassland. Considering the sum of C stocks in the soil, roots and leaf litter, all bamboo species showed significant (p < .001) C storage, i.e. +3.6 kg C m−2 (+64%), +5.3 kg C m−2 (+94%) and +8.6 kg C m−2 (+151%) for P. nigra, P. aurea and P. aureosulcata, respectively. In addition, bamboo's relative basal CO2 efflux (0.007, 0.006 and 0.008 mgCO2‐C g−1 C h−1, respectively) was remarkably lower than in the grassland (0.012 mgCO2‐C g−1 C h−1), though it was only significant for P. aurea. This study highlights that converting temperate permanent grassland into Phyllostachys bamboo plantation can result in net and rapid organic C storage by increasing the total belowground C stability and C input. Further research regarding the net CO2 balance of bamboo‐derived products is still required to fully assess its climate change mitigation potential.