There is increasing evidence that mixed-species forests can provide multiple ecosystem services at a higher level than their monospecific counterparts. Here,
we provide insights into the temporal development of diversity-productivity (DPRs) and diversity-stability relationships (DSRs) in the oldest tree diversity
experiment in the tropics, ‘Sardinilla’ in Panama (established in 2001). We used annually resolved inventory data of tree diameters and heights from 22 plots
with a species richness gradient comprising monocultures, two-, three-, and five-species mixtures of native tree species. Combining tree neighbourhood- and
community-level analyses, we tested the effects of two diversity components, species diversity and structural diversity, on productivity and stability. Over time,
we found a mean overyielding (higher productivity in mixtures compared to monocultures) of about 25-30% in the two- and three-species mixtures and the
highest overyielding at 50% in the five-species mixtures. Tree neighbourhood diversity enhanced community productivity but the effect of species diversity was
stronger and increased over time, while the effect of structural diversity declined. The temporal stability of community productivity increased with increasing
species diversity driven by two principal processes: species asynchrony and overyielding. Along with increased stability, the benefits of mixing on productivity
were highest during a strong El Niño phenomenon, characterized by low precipitation. This suggests a higher resistance of the examined mixtures to droughts.
These results provide new insights into mixing effects in diverse, tropical plantations and highlight the importance of analyses of temporal dynamics for our
understanding of the complex relationships between diversity, productivity and stability.