Using a Life History-Carbon Balance Model for Forest Decline Research

Abstract

In a review of several poorly understood cases of decline of conifer and deciduous forests in North America, Mueller-Dombios et al. (1983) showed that natural senescence and stand uniformity are plausible factors underlying synchronous tree death. The same review described decline of Hawaiian forests of Metrosideros polymorpha (Myrtaceae) where the single generational structure and the maturity of the stands are apparent. The “cohort senescence” theory explains Hawaiian forest dieback as the synchronized death of senescent trees in single-generation stands, and describes these diebacks as naturally occurring cyclic events in primary succession (Mueller-Dombois 1980, 1986, 1987). Long-term studies provide ample evidence of Metrosideros regeneration following these dieback events (Jacobi et al. 1983, 1988). Mueller-Dombois et al. (1983) asserted that the physiological condition of senescing trees, an “internal factor,” deserves equal attention in forest decline research with “external factors,” such as biotic disease and abiotic stresses. This explanatory theory recognizes an important role for external triggering factors that precipitate and synchronize the death of senescent trees.