FACTORS INFLUENCING SUCCESSION:
LESSONS FROM LARGE, INFREQUENT NATURAL DISTURBANCES
Monica G. Turner, William L. Baker, Christopher J. Peterson, and Robert K. Peet
Ecosystems, Vol 1, Issue 6, Nov/Dec 1998, pp. 511-523.
Disturbance events vary in intensity, size, and frequency, but few opportunities exist to study those that are extreme on more than one of these gradients. This paper characterizes successional processes that occur following disturbance events that are exceptional in their great intensity or large size. The spatial variability in disturbance intensity withinlarge, infrequent disturbances (LIDs) often leads to a heterogeneous pattern of surviving organisms. These surviving organisms dictate much of the initial successional pattern on large disturbances where theopportunities for seeds to disperse into the middle of the disturbance are limited. The traditional distinction between primary and secondary succession is insufficient to capture the tremendous variability in succession following LIDs. Disturbance size influences succession where long-distance colonization by propagules is important. Observations from LIDs suggest the following hypotheses about trends in succession with increasing distance from seed sources: (1) the rate of recovery ofcommunity composition will be slower; (2) initial densities of organisms will be lower, with the consequence that competitive sorting will be less important; (3) nucleation processes, in which recovering patches serve as foci for additional colonization and expand spatially, will be more important; and (4) community composition will be initially less predictable. Prediction of succession following LIDs without considering contingencies such as the abundance, types, and spatial distribution of residuals; and distance to seed sources is likely to be unsuccessful for large portions of the landscape. Abundance and spatial arrangement of survivors and arrival patterns of propagules may be the pivotal factors determining how succession differs between intense disturbances of large and small extent.