Carbon-biodiversity relationships in a highly diverse subtropical forest

Carbon-focused climate mitigation strategies are becoming increasingly
important in forests. However, with ongoing biodiversity declines, we
require better knowledge of how much such strategies account for
biodiversity. We particularly lack information across multiple trophic
levels and on established forests, where the interplay between carbon
stocks, stand age and tree diversity might influence carbon–biodiversity
relationships. Using a large dataset (>4,000 heterotrophic species
of 23 taxonomic groups) from secondary, subtropical forests, we tested how
multitrophic diversity and diversity within trophic groups relate to
aboveground, belowground, and total carbon stocks at different levels of
tree species richness and stand age. Our study revealed that aboveground
carbon, the key component of climate-based management, was largely
unrelated to multitrophic diversity. By contrast, total carbon stocks—i.e.
including belowground carbon—emerged as a significant predictor of
multitrophic diversity. Relationships were non-linear and strongest for
lower trophic levels, but non-significant for higher trophic level
diversity. Tree species richness and stand age moderated these
relationships, suggesting long-term regeneration of forests may be
particularly effective in reconciling carbon and biodiversity targets. Our
findings highlight that the biodiversity benefits of climate-oriented
management need to be evaluated carefully, and only maximizing aboveground
carbon may fail to account for biodiversity conservation requirements.