Here we present fossil pollen and charcoal concentrations results from two stratigraphic columns from Isla Mocha (38°19'-38°25'S; 73°57'-73°52'W), Laguna Hermosa (350 m.a.s.l.) and Laguna Huairavos ( 125 m.a.s.l.). These results suggest that the forest of lsla Mocha was maintained at least during the late Holocene,judging from the continuous forest cover during the last 2000 years B.P. The Laguna Hermosa record indicates that the development of the 'olivillo' and mirtaceous forest was interrupted by severa! wet phases, indicated by the dominance of 'canelo' (Drimys winteri) forests most likely associated with flooded or saturated terraines, with the presence of paludal herbs (Cyperaceae-Juncaceae), Gunnera tinctoria and ferns. We discuss the probable effects of tectonic events on the topography and drainage evolution of the island and thus on the vegetation, mainly the emergence of the island beginning 6000 years B.P. and the pronounced uplift during the last 2 000 years B.P. The palynological results are discussed in connection with size structure of monoespecific forests of olivillo in Chile, as these exhibit breaks in the lower to intermediare strata, linked to reduced rates of self-placement. We propose that the maintenance of olivillo forests over long period of time is due to the coexistence of auto- and allogenic processes during the late Holocene. Autogenic processes would be linked to the stability of the community and would be expressed through the gap-phase dynamics. Allogenic processes would be linked to the local changes in soil drainage and landslides, manifestations of tectonic stability. The Laguna Huairavos records shows an abrupt change, from olivillo forests at the base to a canelo forest associated with herbs, paludal taxa and ferns after 1760 years B.P. The presence of abundant microscopic and macroscopic carbon associated with these changes strongly suggest that man-made fires could have been the principal factor that caused the observed succession. This hypothesis is reinforced by two archeological records, both very close to the pollen sites and coevals with the deposition of sediment at Laguna Huairavos. The archeological sites have abundant lithological materials used to cut and wear wood, indicating the importance that the forests had for these cultures, and their clearing for agricultura! and animal use.