Regeneration & Relations, the effects of plant diversity on plant-based ecosystem services for regenerating Neotropical rainforest

Abstract

Tropical forests are among the most diverse ecosystems of our planet and provide important ecosystem services (ES) to humanity: benefits enabling life on earth and making it worth living. A third of the tropical forests in the amazon consist of secondary forests, including clear-cut regenerating forests, playing a crucial role in restoring ES and biodiversity. Synergies between diversity and tropical ES —e.g. aboveground carbon (AGC) storage and Non-Timber Forest Product (NTFP) provisioning— would enable simultaneous restoration; targeting ES restoration would automatically entail restoration of diversity. However, it is unclear if diversity and tropical forest ES are linked for regenerating forests. While primary tropical forests exhibit a significant positive relationship between tree species richness and AGC, such a relationship has not yet been robustly established for regenerating forests. In this report, the relationships between species richness and ES, i.e. carbon storage and NTFP provisioning, were studied in a 25-year-old regenerating forest on a former coffee and cacao plantations in Suriname. After 25 years of regeneration, species richness had recovered to primary forest reference levels, although AGC was still markedly lower. The relationship between species richness and carbon storage was found to be insignificant, as well as between species richness and NTFP provisioning. However, evidence of complementarity and selection effects was found; species-rich vegetation contained more individuals with higher wood density (WD). However, significant impacts of complementarity and selection effects on AGC were hindered by the relatively small size (average DBH < 11 cm) of later successional species with a high wood density (WD > 0.6 g cm-3). We suggest further investigation into species richness-carbon relationships in regenerating forests, to decipher when complementarity, selection, and insurance effects will start to significantly contribute to an increase in AGC. Policymakers are urged to consider the regeneration of tropical forests to be a long-term project, without immediate apparent positive relationships between plant diversity, carbon storage, and NTFP provisioning.