Unifying deterministic and stochastic ecological dynamics via a landscape-flux approach

Li Xu, Denis Patterson, Ann Carla Staver, Simon Asher Levin, Jin Wang

Research output: Contribution to journalArticlepeer-review

Abstract

The frequency distributions can characterize the population-potential landscape related to the stability of ecological states. We illustrate the practical utility of this approach by analyzing a forest–savanna model. Savanna and forest states coexist under certain conditions, consistent with past theoretical work and empirical observations. However, a grassland state, unseen in the corresponding deterministic model, emerges as an alternative quasi-stable state under fluctuations, providing a theoretical basis for the appearance of widespread grasslands in some empirical analyses. The ecological dynamics are determined by both the population-potential landscape gradient and the steady-state probability flux. The flux quantifies the net input/output to the ecological system and therefore the degree of nonequilibriumness. Landscape and flux together determine the transitions between stable states characterized by dominant paths and switching rates. The intrinsic potential landscape admits a Lyapunov function, which provides a quantitative measure of global stability. We find that the average flux, entropy production rate, and free energy have significant changes near bifurcations under both finite and zero fluctuation. These may provide both dynamical and thermodynamic origins of the bifurcations. We identified the variances in observed frequency time traces, fluctuations, and time irreversibility as kinematic measures for bifurcations. This framework opens the way to characterize ecological systems globally, to uncover how they change among states, and to quantify the emergence of quasi-stable states under stochastic fluctuations.

Original languageEnglish (US)
Article numbere2103779118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number24
DOIs
StatePublished - Jun 15 2021

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Ecological system
  • Flux
  • Global stability
  • Landscape

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