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Guohong Zhang

Publications and source records attributed to Guohong Zhang.

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Bifurcation Analysis of a Reaction-Diffusion System with a Cognitive Map Memory Kernel

This paper investigates a single species reaction-diffusion system incorporating a spatiotemporal delay memory kernel, which models the cognitive map of animals, under Neumann boundary conditions. The model can be used to describe the process in which individuals are influenced by historical information during spatial diffusion. An equivalent system construction method with auxiliary variables is introduced to transform the original system into a delay-free coupled reaction-diffusion equation. By employing Fourier modal decomposition and eigenvalue analysis, we conduct stability and bifurcation analyses for both the exponentially decaying weak kernel and the peak type strong kernel, obtaining explicit expressions for the steady state and Hopf bifurcation points. Compared with the model in which the memory term of the continuous-time integral kernel using its own population density, our model exhibits Hopf bifurcations and steady state bifurcations even under a weak kernel because of the introduce of a dynamic cognitive map. This implies that a dynamic cognitive map introduces sufficient flexibility to generate both steady state bifurcations and Hopf bifurcations across a broader range of temporal kernels. Numerical simulations are presented to demonstrate the influence of stable, steady state and Hopf bifurcation regions on the spatiotemporal distribution of solutions.

math.DS

Grazing duration and intensity modulate vegetation dynamics in semi-arid ecosystems with seasonal succession

This study investigates the impacts of grazing duration and intensity on vegetation population dynamics in semi-arid ecosystems characterized by seasonal succession. A novel piecewise periodic model is proposed, dividing the annual cycle into three distinct phases: dry season, growth period and grazing period in wet season. We derive critical thresholds for the durations of the dry season and grazing period that determine the persistence or extinction of a single vegetation species. For two competing species, we analyze how grazing parameters influence competitive outcomes, including exclusion, coexistence, and bistability. Theoretical results are supported by numerical simulations, which illustrate bifurcation diagrams and phase transitions under varying grazing regimes. Our findings provide actionable insights for sustainable grazing management in arid and semi-arid regions.

math.DS

Dynamic Coupling of Infiltration-Soil Moisture Feedback:Emergent Vegetation Patterns in a Water-Vegetation Model

We present a modified water-vegetation model to investigate the mechanistic relationship between infiltration-soil moisture feedback and vegetation pattern in arid/semi-arid ecosystems. Employing Turing pattern formation theory, we drive conditions for diffusion-induced instability and analyze spatiotemporal dynamics near Turing-Hopf bifurcation points. Our key findings include: (i) The system exhibits rich dynamics including multiple stable equilibria, supercritical/subcritical Hopf bifurcations, bubble loops of limit cycles and homoclinic bifurcations. (ii) The system admits Turing-Hopf bifurcation. Using normal form theory, we establish the existence of quasiperiodic solutions and mixedmode oscillations near critical thresholds, providing a mathematical framework for predicting nonlinear ecological regime shifts. (iii) Soil moisture feedbacks govern critical transitions between three distinct ecosystem states: uniform vegetation covering, self-organized spatial patterns (labyrinth/gapped vegetation), and bare soil state, which demonstrates that soil moisture thresholds control the final state selection in this system.

math.DS

Effect of protection zone on the dynamics of a diffusion-advection population-toxicant model

This paper develops and analyzes a diffusion-advection model coupling population dynamics with toxicant transport, incorporating a boundary protection zone. For both upstream and downstream protection zone configurations, we investigate the combined influence of protected zones and key ecological factors on population persistence or extinction. Employing monotone dynamical system theory and eigenvalue analysis, we establish the global dynamics of the population-toxicant coexistence equilibrium. Furthermore, we characterize the parameter dependence governing the stability of the toxicant-only steady state, specifically examining the protected zone length, toxicant effect coefficient on population growth, per-unit contaminant discharge rate, toxicant input rate, diffusion/advection rates, and population natural growth rate. Finally, numerical simulations reveal the complex interplay between the protection zone and toxicant advection rate in significantly shaping population persistence domains.

q-bio.PE