Stand-Level Dieback and Regeneration of Forests in the Galápagos Islands

Stand-level dieback and regeneration of forests in Galápagos are discussed, and related to natural- and man-made disturbances. The dieback of Scalesia pedunculata (Asteraceae) in Galápagos seems to follow the etiology and patterns seen in other pacific island groups. The currently large and synchronized cohorts of this early-successional species, found on Santa Cruz Island, may be explained by severe disturbances such as the natural el Niño phenomenon and human caused fires. It is suggested, that slow-growing species such as Zanthoxylum fagara, Psidium galapageium and Acnistus ellipticus have been suppressed by frequent fires in the highlands of Santa Cruz. The population dynamics of Scalesia pedunculata are suggested to follow a cyclus of 10-20 years duration, caused by senescence in the Scalesia stand, and promoted by extreme stress. Stand-level dieback is also reported from Scalesia cordata, Erythrina velutina and Miconia robinsoniana.