Positive feedbacks and alternative stable states in forest leaf types
Yibiao Zou, Constantin M. Zohner, Colin Averill, Haozhi Ma, Julian Merder, Miguel Berdugo, Lalasia Bialic‐Murphy, Lidong Mo, Philipp Brun, Niklaus E. Zimmermann, Jingjing Liang, Sergio de‐Miguel, G.J. Nabuurs, Peter B. Reich, Ulo Niinements, Jonas Dahlgren, Gerald Kändler, Sophia Ratcliffe, Paloma Ruiz‐Benito, Miguel Á. Zavala, Meinrad Abegg, Yves C. Adou Yao, Giorgio Alberti, Angélica M. Almeyda Zambrano, Braulio Vílchez Alvarado, Esteban Álvarez‐Dávila, Patricia Álvarez-Loayza, Luciana F. Alves, Christian Ammer, Clara Antón‐Fernández, Alejandro Araujo‐Murakami, Luzmila Arroyo, Valerio Avitabile, Gerardo A. Aymard C., Timothy R. Baker, Radomir Bałazy, Olaf Bánki, Jorcely Barroso, Meredith L. Bastian, Jean‐François Bastin, Luca Birigazzi, Philippe Birnbaum, Robert Bitariho, Pascal Boeckx, Frans Bongers, Olivier Bouriaud, Pedro H. S. Brancalion, Susanne Brandl, Francis Q. Brearley, Roel Brienen, Eben N. Broadbent, Helge Bruelheide, Filippo Bussotti, Roberto Cazzolla Gatti, Ricardo G. César, Goran Češljar, Robin L. Chazdon, Han Y. H. Chen, Chelsea Chisholm, Hyunkook Cho, Emil Cienciala, Connie J. Clark, David B. Clark, Gabriel Dalla Colletta, David A. Coomes, Fernando Cornejo Valverde, José Javier Corral‐Rivas, Philip M. Crim, Jonathan Cumming, Selvadurai Dayanandan, André Luís de Gasper, Mathieu Decuyper, Géraldine Derroire, Ben DeVries, Ilija Djordjević, Jiří Doležal, Aurélie Dourdain, Nestor Laurier Engone Obiang, Brian J. Enquist, Teresa J. Eyre, Adandé Belarmain Fandohan, Tom M. Fayle, Ted R. Feldpausch, Leandro Valle Ferreira, Leena Finér, Markus Fischer, Christine Fletcher, Jonas Fridman, Lorenzo Frizzera, Javier G. P. Gamarra, Damiano Gianelle, Henry B. Glick, David J. Harris, Andy Hector, Andreas Hemp, Geerten Hengeveld, Bruno Hérault, John Herbohn, Martin Herold, Annika Hillers
Abstract
The emergence of alternative stable states in forest systems has significant implications for the functioning and structure of the terrestrial biosphere, yet empirical evidence remains scarce. Here, we combine global forest biodiversity observations and simulations to test for alternative stable states in the presence of evergreen and deciduous forest types. We reveal a bimodal distribution of forest leaf types across temperate regions of the Northern Hemisphere that cannot be explained by the environment alone, suggesting signatures of alternative forest states. Moreover, we empirically demonstrate the existence of positive feedbacks in tree growth, recruitment and mortality, with trees having 4-43% higher growth rates, 14-17% higher survival rates and 4-7 times higher recruitment rates when they are surrounded by trees of their own leaf type. Simulations show that the observed positive feedbacks are necessary and sufficient to generate alternative forest states, which also lead to dependency on history (hysteresis) during ecosystem transition from evergreen to deciduous forests and vice versa. We identify hotspots of bistable forest types in evergreen-deciduous ecotones, which are likely driven by soil-related positive feedbacks. These findings are integral to predicting the distribution of forest biomes, and aid to our understanding of biodiversity, carbon turnover, and terrestrial climate feedbacks.