Transient Instability and Patterns of Reactivity in Diffusive-Chemotaxis Soil Carbon Dynamics

TL;DR

This paper investigates how transient dynamics and reactivity can induce pattern formation in a soil bacteria and carbon model, revealing mechanisms beyond traditional Turing instability, especially in two-dimensional systems.

Contribution

It uncovers how transient growth and reactivity can lead to pattern formation outside Turing unstable regimes, emphasizing the role of system geometry and bistability.

Findings

Transient dynamics can induce patterns without Turing instability.

Bistable regions with transient growth are present in 2D but not 1D.

Reactivity analysis reveals new pattern formation mechanisms.

Abstract

We study pattern formation in a chemotaxis model of bacteria and soil carbon dynamics as an example system where transient dynamics can give rise to pattern formation outside of Turing unstable regimes. We use a detailed analysis of the reactivity of the non-spatial and spatial dynamics, stability analyses, and numerical continuation to uncover detailed aspects of this system's pattern-forming potential. In addition to patterning in Turing unstable parameter regimes, reactivity of the spatial system can itself lead to a range of parameters where a spatially uniform state is asymptotically stable, but exhibits transient growth that can induce pattern formation. We show that this occurs in the bistable region of a subcritical Turing bifurcation. Intriguingly, such bistable regions appear in two spatial dimensions, but not in a one-dimensional domain, suggesting important interplays between geometry, transient growth, and the emergence of multistable patterns. We discuss the implications of our analysis for the bacterial soil organic carbon system, as well as for reaction-transport modeling more generally.