Document: CEC-3-63-13

Ecosystem and physical control of tree growth in two Chilean temperate forests.

PEREZ, C.*, J.J.ARMESTO, J.C.ARAVENA and M.CARMONA

Universidad de Chile. Santiago, Chile ¹

Abstract:
We investigated the seasonal patterns of tree growth and the main physical and ecosystem variables that control these patterns in two temperate rainforests in the coastal range of Chilo Island (42 30'S), southern Chile: A conifer-dominated and a mixed-broadleaf Nothofagus-Podocarpus forest. In each forest, dominant canopy trees [N=10 for Fitzroya cupressoides (Cupressaceae), and N=5 trees each for Podocarpus nubigena (Podocarpaceae) and Nothofagus nitida (Fagaceae)] were monitored for diameter increment using high-resolution, electronic band dendrometers. Hourly records of tree cambial activity were taken from 1997-1999. Tree hydration levels were recorded by capacitance sensors implanted in the phloem tissue. Simultaneously, environmental variables (air and soil temperature, moisture, monthly precipitation) and ecosystem processes (carbon, nitrogen inputs in litterfall, net nitrogen and phosphorous mineralization rates in soil) were measured in situ. Results revealed marked seasonality of tree growth in these temperate communities. Growth is shut down in winter and re-initiated in spring. Maximum growth occurred in late spring for both Nothofagus and Podocarpus, but it varied greatly among individuals for Fitzroya. Growth rates decreased towards summer and fall in all species. Growth of Fitzroya was temporally interrupted during rainless summer months. Principal Component Analysis suggest that in the mixed forest higher tree growth is associated with reduced C/N ratio in litterfall. In the conifer forest tree growth is more strongly associated with tree hydration and potential N mineralization. Annual radial increment varied from 0.11 to 1.4 mm in Fitzroya, from 0.037 to 3.2 mm in Nothofagus and from 0.38 to 1.5 mm in Podocarpus. Inter-individual differences are attributed to tree ages and crown exposure to light Supported by Presidential Chair in Science in Science (JJA) and A. W. Mellon Foundation.

Keywords: Radial tree growth, Southern temperate forests, Internal N cycle

This abstract is being presented at: 3:30 PM in session:
Poster Session #17: Vegetative Analysis.