Establecimiento de cuatro especies de Quercus en el sur de la ...

Whithin population variability influences early seedling establishment on four Mediterranean Oaks
DISCUSSION
In this study we identified environmental and intrinsic factors that may affect
the early establishment of four Mediterranean oak species. Our more interesting
results was that within population variability as determined by maternal origin affects
different phases of establishment and can modify the responses of seedlings along
resource gradients.
Emergence
For three of the studied species, light availability influenced time to emergence,
being in general a negative factor (the more incident radiation, the lesser time to
emergence). In areas with more incident radiation the soil temperature could be
higher, and this could acelerate the germination and then shortens the time to
emergence (Pugnaire at al., 2006). However, maternal traits modified the effects of
light availability on emergence time of the two deciduous species. Light effects were
negative, neutral or even positive depending on the mother tree. These differences
between mothers can be related to seed moisture content, which happened to differ
among maternal plants. Delayed emergence of seedlings has been related to hypocotyl
dormancy, which is associated to higher seed moisture content (Merouani et al.,
2001). On the other hand, we found that larger seeds of Q. suber and Q. faginea
emerged earlier. This effect of seed mass on time to emergence has not been observed
in other species (Castro, 1999; Jones et al, 1997), but it may be related to speciesspecific
seed size and the ability of seeds to have a storage function. In our case, early
emergence of larger seeds could also be a consequence of a less time of germination
that has been found for other oak species (Gómez, 2004a).
Another interesting result was the delayed emergence that was observed for a
proportion of seedlings in all species (between 2.7 to 5.5). This phenomenon has been
reported for Q. ilex by Gómez (2004b), who found that some acorns germinated but
remained shootless during the summer and emerged when environmental conditions
became favourable. This strategy may thus represent a resistance mechanism against
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