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Positive feedbacks and alternative stable states in forest leaf types

Published Article

Global

Publication date: May 31, 2024

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Global data and simulations show evergreen and deciduous forests form alternative stable states driven by strong positive feedbacks in growth, survival, and recruitment. These feedbacks create bistability, hysteresis, and hotspots in ecotones, shaping biome distribution, biodiversity, and climate‑carbon dynamics.

Subject Tags

  • Forest
  • Biodiversity
  • Life Sciences

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.

Citation

Zou, Y., Zohner, C.M., Averill, C., Ma, H., Merder, J., Berdugo, M., Bialic-Murphy, L., Mo, L., Brun, P., Zimmermann, N.E. and Liang, J., 2024. Positive feedbacks and alternative stable states in forest leaf types. Nature Communications, 15(1), p.4658. https://doi.org/10.1038/s41467-024-48676-5

TNC Authors

  • The Nature Conservancy