INVESTIGADORES
GRAU Hector Ricardo
artículos
Título:
Tree life histories in a montane subtropical forest: species differ independently by shade-tolerance, turnover rate and substrate preference
Autor/es:
EASDALE, T; HEALEY, J; GRAU, HR; MALIZIA, A
Revista:
JOURNAL OF ECOLOGY (PRINT)
Editorial:
Blackwell
Referencias:
Lugar: Londres; Año: 2007 vol. 95 p. 1234 - 1249
ISSN:
0022-0477
Resumen:
1.
To investigate life-history differentiation and an objective functional classification of
tree species we analysed the demography of 29 species in subtropical montane forests in
north-western Argentina.
2.
We computed 13 growth, demographic, abundance and distribution variables based
on: (i) two 5-year re-measurements of stems
¡Ý
10 cm diameter at breast height (d.b.h.)
in 8 ha of old growth forest and 4 ha of secondary forest; (ii) assessments of tree crown
illumination; and (iii) sapling counts under shade and on landslides.
3.
We assessed the potential confounding effects of stem size and crown illumination on
absolute stem diameter growth rate for the 24 most abundant species. As diameter
increased, one species showed significant increases in growth rate and five showed
significant reductions. Seventeen species grew significantly faster with increased exposure
to light and we controlled for this confounding effect in the computation of diameter
growth rates for subsequent analyses.
4.
A principal component analysis resulted in three meaningful and interpretable axes
of demographic variation across species. The first axis (interpreted as shade tolerance)
indicates that trees of species with inherently high growth rates tend to have wellexposed
crowns at 10¨C30 cm d.b.h., have high density of trees in secondary forest and
are less tolerant of shade.
5.
The second axis (turnover) shows that in old-growth forest short-lived species, with
high mortality rates, size-class distributions with a steep negative slope and low
dominance, persist due to high rates of recruitment (to
¡Ý
10 cm d.b.h.).
6.
The third axis indicates that species that colonize landslides have lower tree
recruitment rates and greater growth variability in secondary forest, reflecting spatio/
temporal differences in species¡¯ recruitment linked to differences in their substrate
requirements for regeneration.
7.
Maximum height and diameter are correlated with the first and second axes,
indicating that higher rates of both growth and survival permit some species to attain
large size.
8.
All three demographic axes depict separate trade-offs that confer competitive
advantage to each ¡®demographic type¡¯ under contrasting ecological conditions (of light
availability, disturbance frequency and disturbance intensity), thus underpinning
species¡¯ coexistence in dynamic forest landscapes.