Abstract

Both theory and empirical evidence support the hypothesis that diversity stabilizes productivity in primary producer communities. In model systems such as grasslands, stabilizing effects have been linked to three key processes: species asynchrony, overyielding and species interactions. However, it is unclear whether these same mechanisms also promote stability in other plant communities. Using tree ring data from permanent forests plots, we explore the relationship between diversity and aboveground wood production (AWP) in forests across Europe. We show that although diversity has a strong stabilizing effect on AWP , the processes behind this positive association differ from those acting in other, more dynamic, systems. Of the three mechanisms we tested, only overyielding was found to operate in much the same way as previously reported by other studies, and emerged as a general, albeit weak, stabilizing force. Asynchrony in species responses to fluctuating environmental conditions was strongly stabilizing. However, its effects were largely limited by the slow turnover rates which characterize forest ecosystems. For this very reason we also found that species interactions tended to promote – rather than deter – stability in individual species growth rates, the opposite of what is generally found in grasslands. Together, our results shed light on the central role of diversity as a driver of AWP stability in forests, and bring us closer to linking patterns and processes in natural ecosystems.