Divergence, convergence, and self-organization in landscapes

sMany theories, old and new, of landscape and earth-surface system developm ent involve concepts of self-organization. There are at least eleven distin ct definitions of self-organization in the literature that are relevant to landscapes. Some have profoundly different implications with respect to the nature and trajectories of landscape evolution and earth-surface system be havior, including whether evolution is convergent or divergent, whether ent ropy or energy dissipation is maximized or minimized, the role of chaos, an d the mechanisms by which self-organized patterns are generated. Despite th ese differences, most self-organization concepts can be broadly aggregated into two categories: those concerned with the evolution of order and regula rity in the aggregate or ensemble properties of the landscape, and those co ncerned with the differentiation of landscapes into more diverse spatial un its. This paper presents a theory of spatially divergent self-organization related to the latter, showing that autogenic differentiation is directly l inked to dynamical instability and chaos. The determination of the self-org anization properties of a landscape should be a starting point rather than a goal of geographic explanation. The extent to which field-testable hypoth eses are generated, or explanations provided based on process mechanics or landscape history, will ultimately determine the utility of self-organizati on concepts and methods in physical geography.