Comparative morphologies and life histories amongst montane tree species in north-western Argentina

Abstract

Co-existing broadleaved sub-tropical tree species were compared in two separate
montane forests. Axes of morphological differentiation were identified amongst species
and their functional significance evaluated by testing their links with species' (a)
recruitment patterns across resource gradients and (b) demographic life-history
variables. At Los Toldos valley (Salta), 14 morphological, reproductive and
phenological traits were measured in 41 species. These were complemented by (i) a
census of trees (2: 5 cm dbh) in forty-six 0.075 ha forest plots distributed across a wide
range of soil fertilities and (ii) a molecular phylogeny. At San Javier (a nature reserve in
Tucum,111), 15 ecomorphological traits and 13 demographic, abundance, and distribution
variables were measured in 29 species. Demographic information was obtained over a
10-year census period in 12 ha of permanent sample plots (trees 2: IO cm dbh) in
secondary and old-growth forest, complemented by estimations of tree crown exposure
to light and counts of saplings growing under shade. At both sites a major non-random
axis of covariation between leaf traits and wood density reflects an evolutionary tradeoff between rapid acquisition/use of resources and high conservation of resources. The
functional significance of this ecomorphological axis was supported at Los Toldos by:
(a) phylogenetically-controlled comparisons which indicate that trait-associations partly
resulted from recurrent evolution in different phylogenetic lineages and (b) observations
that species with resource conservation attributes recruit more commonly where light or
soil resources are in short supply. At San Javier, quantitative comparisons of species'
demographic performances provided an objective classification of tree life-histories
constituted by three axes: light-demand, population turnover and regeneration
requirements. The first two life-history axes match two ecomorphological axes; species
with short life-spans and fast population turnover rates have attributes of high resource
acquisition and short stature, and the light-demand axis was related to a 'physiognomic '
axis.

Date of Award	Jan 2006
Original language	English
Awarding Institution	University of Wales, Bangor
Sponsors	CONICET, Buenos Airies & Overseas Research Student Awards Scheme
Supervisor	John Healey (Supervisor)