An area of mixed deciduous and evergreen Nothofagus forest at 1000-1050 m near timberline in South-central Chile wa s studied to determine the influence of the tree dominants on the distribution and dominance of plants in the understorey, the bamboo Chusquea tenuiflora was found to be mor e frequent and taller under the evergreen Nothofagus betuloides. Nearl y all other species wer e mor e abundant and large r under the deciduous Nothofagus pumilio. Th e persistence of the snow cover is less under N. betuloides which results in an effectively longe r vegetative period under the evergreen trees. C. tenuiflora is well adapted by its capacity to immediately spring into an erect position to take advantage of the earlier snowmelt, and its vigorous growth suppresses the other understorey compoments. In the successional trend from mixed Nothofagus forest towards evergreen forest, C. tenuiflora would be expected to increase in size and abundance and play an increasingly controlling role in the process of forest regeneration.