Effects of plant diversity on productivity strengthen over time due to trait-dependent shifts in species overyielding by Zheng, L, Barry, KE, Guerrero-Ramírez, NR, Craven, D, Reich, PB, Verheyen, K, Scherer-Lorenzen, M, Eisenhauer, N, Barsoum, N, Bauhus, J, Bruelheide, H, Cavender-Bares, J, Dolezal, J, Auge, H, Fagundes, MV, Ferlian, O, Fiedler, S, Forrester, DI, Ganade, G, Gebauer, T, Haase, J, Hajek, P, Hector, A, Hérault, B