The potential of plantations to restore ecosystem services, a case study from Ghana

The role of plantations for restoring humid forest ecosystems is subject to intense debate. Some studies suggest that plantations are inferior to secondary forests in most ecosystem services. In contrast, other studies emphasise the role of planted trees that could catalyse an accelerated development towards late-successional forests. Our study analyses a unique dataset of old (>40 years) unmanaged timber plantations. Planted species were Aucoumea klaineana, Cedrela odorata, Tarrietia utilis, and Terminalia ivorensis. We compare these to secondary forests, and pristine primary stands. Our results indicate that in the unmanaged plantations, species-rich stands with high biomass evolved. The carbon stocks of the unmanaged plantations exceeded the secondary forest and had similar levels to the primary stands. The biomass of the naturally regenerated trees in the plantations was similar to secondary forests. Not surprisingly, timber value of the plantations surpassed both primary forests and secondary forests. Results were more mixed for biodiversity attributes. Plantations of Aucoumea klaineana had lower diversity values than the primary and secondary forests. However, other species, especially plantations of Cedrela odorata, had similar diversity to primary and secondary forests. Species with high conservation value were present in all three ecosystem types. Above-ground carbon stocks in plantations were highest, and there were no statistical differences in below-ground carbon stocks. Our results indicate that plantations could play a role in rapidly accruing carbon in tropical landscapes.