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

Reforestation with Quercus ilex L. and Q. suber L. by direct seeding and planting in southern Spain
No clear conclusion can be drawn as regards survival in 3‐year‐old seedlings.
Thus, Q. suber exhibited medium rates (about 50% the first year) that were
comparable to those for direct‐seeded plants, and Q. ilex had very low values (25 %)
that departed significantly from those for the other methods.
These performance differences can seemingly not be explained in terms of the
morphological variables studied. Previous studies aimed at identifying morphological
attributes allowing seedling field performance to be predicted found either no definite
relationships (Zida et al., 2008; Palacios et al., 2009) or relationships that changed with
the meteorological conditions of the planting year (Del Campo et al., 2010). Palacios et
al. (2009) claim that the effect of seedling quality must be studied jointly with those of
other environmental factors —particularly, those with a high potential impact on
reforestation. Thus, appropriate soil preparation and planting date selection, with
provision for the local climate, might be the most influential factors for successful
reforestation. Nursery cultivation variables may also have a prominent effect on postplanting
establishment (Menzies et al., 2001; South et al, 2001; Villar‐Salvador et al.,
2004a). Container type and size are two such variables. Larger containers allow the
development of deeper tap roots capable of colonizing increased volumes and
absorbing more water as a result, thereby facilitating the establishment of seedlings —
the greatest limitation for which is known to be imposed by summer droughts (Pemán
et al., 2006; Chirino et al., 2008). The containers used to grow 3‐year‐old Q. ilex
seedlings were considerably smaller than those for 3‐year‐old Q. suber seedlings.
Moreover, removal of seedling roots from the soil after 8 months of growth in the field
revealed that the nursery seedlings had developed few new roots outside of the
nursery container root volumen; by contrast, the roots of direct‐seeded plants had
grown more vertically than horizontally. This effect may have been critical for 3‐yearold
Q. ilex oaks, which produced less deep roots than the others and may partly
account for their poor survival by effect of their strengthening container constraints on
root growth.
Although seedlings with an increased root/shoot ratio can be expected to
survive quite well in dry environments (Lloret et al., 1999), we found no lower
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