Authors’ contributions

C.J. Chu, Y.H. Zhang and W. Lin conceived and designed the study. Y.H. Zhang and W. Lin performed the experiments and data analysis. B.H. Li conducted the forest census. Y.H. Zhang and W. Lin contributed materials collection. W. Lin wrote the paper. C.J. Chu, S.A. Queenborough, M. Ni, Q. He, and Y.H. Zhang revised the paper.