INVESTIGADORES
MARTINEZ PASTUR Guillermo Jose
artículos
Título:
Photosynthetic plasticity of Nothofagus pumilio seedlings to light intensity and soil moisture
Autor/es:
G MARTÍNEZ PASTUR; MV LENCINAS.; P PERI; M ARENA
Revista:
FOREST ECOLOGY AND MANAGEMENT
Referencias:
Año: 2007 vol. 243 p. 274 - 282
ISSN:
0378-1127
Resumen:
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Nothofagus seedlings often
survive and grow slowly for a long time in the shaded understory. This creates
a seedling bank with a potential advantage in reestablishing canopy
disturbances. To manage primary forests more effectively, it is important to
understand the basis of plant regeneration ecophysiology, and their plasticity
to changes in environmental factors. The objective was to evaluate the
photosynthesis plasticity of N. pumilio seedlings to light intensity and
soil moisture gradients; and to relate them with silvicultural prescriptions.
Six treatments with three light intensities (4%, 26% and 64% of the natural
incident irradiance) and two soil moistures levels (40-60% and 80-100% soil
capacity) were assayed under greenhouse controlled conditions. CO2
gas exchanges were measured every month on seedlings growing in each condition.
In the shaded treatments seedlings grow below their optimum photosynthetic
potential (leaf light-saturated net photosynthesis rate of 5.1 µmol CO2
m-2 s-1) compared with the lighted treatments by
improving their photosynthetic performance (8.3-8.4 µmol CO2 m-2
s-1). Seedling growing under low soil moisture conditions had higher
leaf light-saturated net photosynthesis rate than plants grown under 80-100%
soil water capacity (7.8 µmol CO2 m-2 s-1 and
6.6 µmol CO2 m-2 s-1, respectively). When
light (up to 150-200 µmol m-2 s-1) and soil moisture
(40-60% soil capacity) levels were favorable, seedling plants could exhibit
their maximum photosynthetic capacity. If one of these factors became limiting,
the plants reduced their photosynthetic rate, e.g. Nohofagus pumilio
seedlings with enough light and high levels of soil moisture, probably
decreased their growth and fine roots activity. For this, application of
silviculture systems must take into account the changes in both factors (light
and soil moisture) for maximize the growth potential in the natural
regeneration. These findings must be combined with morphological variables at a
whole-plant, shoot, crown and leaf levels to determine the optimum growth
conditions.