ABSTRACT
While it is not always explicitly acknowledged, most forest ecologists appear to (at least implicitly) accept the central tenets of complexity science. This recognition has many antecedents, but our understanding of the ubiquity of natural disturbance clearly provided a foundation for a regime shift in our thinking about forest ecosystems (Loucks, 1970; Heinselmann, 1973). Early models of system reorganization following disturbance were largely deterministic and focused on clearly defined pathways of system reorganization to restore a steady state (Bormann and Likens, 1979). As late as the 1980s, ecologists were still debating whether there was empirical evidence of multiple successional pathways within forests (Abrams et al., 1985). In the last 30 years, however, it has become clear that there is far more variability and unpredictability in forest dynamics than early models of succession imagined, even in systems with minimal human impacts (Pacala et al., 1996; Daniels, 2003). But it seems equally clear that there are strong forces of self-organization within forests and that certain features of forest ecosystem structure and function are both highly resilient and broadly predictable (Pacala et al., 1996). A major attraction of complexity science is that it provides a body of theory that can reconcile the instability and unpredictability of multiple successional pathways with the more constrained and predictable dynamics of classical succession theory (Haeussler, 2011). But while succession theory has emphasized recurring cycles of disturbance, regrowth, maturation and redisturbance, complexity science helps us to situate such cycles within a larger framework of ceaseless environmental change, adaption and uncertainty.
