Extinction Probabilities and the Changing Age Structure of Redwood Forests

Survival of coast redwoods is modeled as a stochastic process of individual tree and neighborhood-wide survival and reproduction processes. Age-dependent seed and sprout production capacities, as well as probabilities of death and site availability, are estimated for various levels and kinds of site disturbances which may occur in the future. Analyses of these processes indicate that, in the remaining areas of old-growth, coast redwoods have a small probability of extinction due to natural processes within neighborhoods. Management to control mortality and increase successful reproduction can increase survival probabilities and the chances of maintaining an all-aged structure. However, large areas can be destroyed by many agencies in addition to clear-cutting, and their frequency may well increase in the future. While supplemental planting can easily prevent extinction, the survival processes in redwoods which are now or are soon to be converted to almost completely young age-class trees is not yet well known. A conservative strategy requires heavy restrictions on conversion of old-growth, all-aged forest neighborhoods into young, even-aged neighborhoods.