Document: MAU-3-69-9

Tree regeneration responses in a lowland Nothofagus-dominated forest after bamboo dieback in South-Central Chile.

GONZALEZ, M.E.* ^1,2

Universidad Austral de Chile, Valdivia, Chile. ¹
University of Colorado, Boulder, CO, USA. ²

Abstract:
The bamboo Chusquea quila (Poaceae:Bambuseae) is the most abundant understory species of Nothofagus-dominated forests at low elevations in the Chilean Lake District. This species strongly inhibits the establishment and growth of tree seedlings, especially those of the genus Nothofagus. At intervals of many years, this bamboo flowers synchronously and dies, creating large-scale disturbances. The objective of this study was to determine the influence of bamboo dieback on tree regeneration, especially of shade-intolerant species. The forest studied is a remnant old-growth forest dominated by emergent individuals of N. obliqua and Eucryphia cordifolia above a main canopy formed by evergreen tree species. Tree seedlings established prior to bamboo dieback were recorded in six gaps densely covered by bamboo. After the dieback event in the early 1990's, recruitment, height growth and survivorship were monitored in four gaps during two growing seasons. The advance regeneration consisted mainly of the shade-tolerant species Aextoxicon punctatum, Laurelia philippiana, and Amomyrtus luma. These species, together with E. cordifolia, accounted for over 90 % of the total individuals in gaps. During the following two seasons, c. 40 % of the advance regeneration either died or was damaged. Root suckers of E. cordifolia and L. philippiana were taller and grew faster than the seedlings of other species. New recruitment resulted in the synchronized establishment of shade-intolerant tree seedlings such as N. obliqua, Aristotelia chilensis, and E. cordifolia. These species recruited into the gaps almost entirely during the first season right after the bamboo dieback. However, by the end of the second season, these species had a lower density due to a combination of lower recruitment rate, shortened recruitment period, and greater mortality rate compared to the shade-tolerant species. New bamboo seedlings grew faster and were more abundant than tree seedlings, except for root suckers of E. cordifolia. Seedlings of N. obliqua competed poorly with bamboo seedlings; their successful recruitment may require bamboo flowering coincident with a mast seed year for the tree species.

Keywords: understory influences, gaps.

This abstract is being presented at: 10:30 AM in session:
PLANT DEMOGRAPHY