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

Capítulo 3
environmental conditions (Beckage and Clark, 2003). Moreover, natural shading in the
experimental site was mainly produced by Q. ilex, Pinus pinaster and Cistus ladanifer.
The last two species alter physico‐chemical properties of the top‐soil by emiting
allelochemical compounds or modifying the amount of nutrients (Gallardo, 2003;
Gómez–Aparicio et al., 2005; Puerta‐Piñero, 2006). These plant‐plant interactions take
place in different signs depending on the nurse plant and could hide the specific
responses to light availability per se. In fact, Perez‐Ramos et al. (2010) found that light
and nutrient availability are negatively related, therefore the effect of each factor
isolated may be masked.
According to a similar experiment carried out in Sierra Nevada (Spain) (Gómez‐
Aparicio, 2008), light increased aboveground biomass and leaf mass fraction of Q.
pyrenaica. As canopy intercepts rainfall during the growing season (Aussenac, 2000),
shaded sites could be occassionaly drier, so oak seedlings growing in open and wet
areas could be favorished, even although this species is shade tolerant in early life
stages (Quero et al., 2006). On the other hand, stem height of Q. ilex increased on the
shade. This effect have been previously observed in plants growing in areas with a
reduced R:FR ratio (Ziegenhagen and Kausch, 1995; Ammer, 2003). In this experiment
no deep shaded microsites were represented as they are scant in the study area so
other strong negative relations between light and growth are rarely to appear.
Moreover, the studied species are in general, intermediate or good shade tolerant
(Cardillo and Bernal, 2006, Quero et al., 2006, Pérez‐Ramos et al, 2010).
As observed on survival and establishment, soil moisture during the growing
season affected positively Quercus growth and biomass. Holm oak was not influenced
by soil moisture, maybe due to its higher drought tolerance (Mediavilla and Escudero,
2003; David et al., 2007).
Competition between herbs and woody seedlings is mainly for water (Davis et
al., 1999; Rey Benayas et al., 2007). In the present study the herbaceous layer was
related to a decrease in RGR a and aerial biomass and to an increase of stem height in
Q. ilex at the beginning of the growing season. Holmgren et al. (2000) found similar
herb‐effect on Chilean woody seedlings. Competition could be, in this case, for light as
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