Volume 25, Issue 3, March 2015
Index of content:
- FOCUS ISSUE: NONLINEAR DYNAMICS FOR PLANET EARTH
25(2015); http://dx.doi.org/10.1063/1.4897912View Description Hide Description
Changes in our climate and environment make it ever more important to understand the processes involved in Earth systems, such as the carbon cycle. There are many models that attempt to describe and predict the behaviour of carbon stocks and stores but, despite their complexity, significant uncertainties remain. We consider the qualitative behaviour of one of the simplest carbon cycle models, the Data Assimilation Linked Ecosystem Carbon (DALEC) model, which is a simple vegetation model of processes involved in the carbon cycle of forests, and consider in detail the dynamical structure of the model. Our analysis shows that the dynamics of both evergreen and deciduous forests in DALEC are dependent on a few key parameters and it is possible to find a limit point where there is stable sustainable behaviour on one side but unsustainable conditions on the other side. The fact that typical parameter values reside close to this limit point highlights the difficulty of predicting even the correct trend without sufficient data and has implications for the use of data assimilation methods.
25(2015); http://dx.doi.org/10.1063/1.4906951View Description Hide Description
Many biological populations fluctuate in synchrony over large geographic regions. This behavior may increase the chance of extinction. The combination of time-scale separation between interacting species and weak spatial linear diffusive coupling is one mechanism that can generate synchrony; however, accounting for travel time between habitat patches may destabilize this synchrony. Here, we show that ubiquitous behavioral aspects of dispersal (e.g., predator avoidance), implemented as nonlinear diffusive coupling, may also destabilize synchrony. In addition, these aspects interact with travel-time delays and amplify mechanisms that destroy synchrony. Our work suggests that dispersal-induced synchrony is more rare than typically assumed.