Resource-consumer dynamics in drylands: modeling the role of plant-plant facilitation-competition shifts with a piecewise system
arxiv(2024)
摘要
In drylands, water availability determines plant population densities and
whether they cooperate via facilitation or compete. When water scarcity
intensifies, plant densities decrease and competition for water surpasses the
benefits of soil improvement by facilitator plants, involving an abrupt shift
from facilitation to competition. Here, we model this facilitation-competition
shift using a piecewise system in a resource species such as grasses studying
its impact on a resource-consumer dynamical system. First, the dynamics of each
system are introduced separately. The competitive system, by setting conditions
to have a monodromic equilibrium in the first quadrant, has no limit cycles.
With a monodromy condition in the same quadrant, the cooperative system only
has a hyperbolic, small amplitude limit cycle, allowing for an oscillating
coexistence. The dynamic properties of the piecewise system become richer. We
here prove the extension of the center-focus problem in this particular case,
and from a weak focus of order three, we find 3 limit cycles arising from it.
We also study the case assuming continuity in the piecewise system. Finally, we
present a special and restricted way of obtaining a limit cycle of small
amplitude in a pseudo-Hopf bifurcation type. Our results suggest that abrupt
density-dependent functional shifts, such as those described in drylands, could
introduce novel dynamical phenomena. Our work also provides a theoretical
framework to model and investigate sharp density-dependent processes in
Ecology.
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