Semi-arid ecosystems can exhibit striking vegetation patterns, which may have no characteristic size of patchiness. Elucidating local scale processes that generate these macroscopic patterns is of fundamental ecological importance. In addition, they may provide insights and tools to forecast the future dynamics of these highly vulnerable ecosystems that are prone to abrupt, irreversible shifts in vegetation cover, often resulting in desertification. I ask what information can be inferred from spatial vegetation patterns about an ecosystem and the processes driving it. I approach this question from two related angles. The first is from the context of scale and strength of underlying ecological interactions in a landscape. The second is from the context of regime shifts and spatial indicators of the same.

I begin by reviewing previous work done on bistability in ecosystems and spatial patterns indicative of approaching regime shifts. I briefly discuss the pros and deficiencies of existing spatial early warning signals of abrupt regime shifts (also called,discontinuous transition). I then propose and analyse a new metric, the power spectrum. I demonstrate that in combination with another widely used early warning signal - the probability distribution of vegetation patches in the system, it could provide a robust tool for detection of imminent discontinuous transitions.

The nature of regime-shifts (continuous/discontinuous) is determined by the underlying interactions in the system. Within this framework, I carry out further investigations of spatial patterns and the processes that they are signatures of. Most ecological interactions between species of the same trophic level (such as between different plants) can be simplified into two basic types – competition and facilitation. The relative scales over which interactions of each type are operational, could potentially determine the nature of the spatial patterns observed in vegetation over a landscape. I use cellular automaton models to simulate conditions with different scales of competitive and facilitative interactions in a system and analyse the resultant spatial patterns for signatures of these underlying rules.