Global dynamics of a size-structured forest model

TL;DR

This paper analyzes a size-structured forest growth model, establishing conditions for permanence, existence of a global attractor, and stability of equilibrium states under certain biological assumptions.

Contribution

It introduces a novel approach to the renewal equation for forest dynamics, proving permanence, global attractor existence, and stability results under weak assumptions.

Findings

Existence of a compact global attractor for the model.

Conditions for the model's permanence.

Stability of a unique equilibrium under monotonicity assumptions.

Abstract

We study a size-structured model proposed in [1] C. Barril, \`A. Calsina, O. Diekmann, J. Z. Farkas, On competition through growth reduction, e-print arXiv:2303.02981, to describe the dynamics of trees growth in the forest. Our approach to the associated renewal equation is rather different from the methods in [1] and is based on ideas developed in [2] F. Herrera, S. Trofimchuk, Dynamics of one-dimensional maps and Gurtin-MacCamy's population model. Part I: asymptotically constant solutions, Ukrainian Math. J., (in Memory of O. Sharkovsky), 75 (2023), 1635-1651, https://doi.org/10.3842/umzh.v75i12.7678. Assuming relatively weak restrictions on the reproduction, death and growth rates $\beta, \mu, g$, we establish the permanence properties of the semiflow $\frak F^t$ generated by the renewal equation and prove that it possesses a compact global attractor of points $\mathcal A$. Next we show that the opposite types of monotonicity of $\beta, g$ assure that $\frak F^t$ is also monotone and that in this case $\mathcal A$ coincides with a unique asymptotically stable equilibrium attracting neighbourhoods of compact sets with non-zero initial data.