Can native shrubs facilitate the early establishment of contrasted co-occurring oaks in Mediterranean grazed areas?

Costa A., Villa S., Alonso P., García-Rodríguez J.A., Martín F.J., Martínez-Ruiz C. y Fernándes-Santos B. (2017) - Can native shrubs facilitate the early establishment of contrasted co-occurring oaks in Mediterranean grazed areas? - JOURNAL OF VEGETATION SCIENCE

Questions: Can shrubs (Cytisus multiflorus) and large herbivore exclusion
(fence) facilitate seedling survival and growth of marcescent and sclerophyllous
oaks (Quercus pyrenaica vs Q. ilex subsp. ballota) under a bioclimatic limit in
Mediterranean grazed areas?
Location: Open oakwoodlands, central-western Spain.
Methods: A 2-yr field experiment was conducted by planting 200 seedlings of
each Quercus species under four different treatments combining the influence of
nurse shrubs and fencing on Quercus seedling survival and growth.
Results: Cytisus multiflorus enhanced poor Quercus seedling survival found in the
study area, at least during the first 2 yr after planting and particularly during the
first dry season. The improvement in soil organicmatter under the shrub canopy
may have contributed to this positive effect, which was more pronounced on
Q. pyrenaica seedlings. Seedling herbivory did not seem to be a limitation to survival.
Increased seedling growth in both species was also very low, and no
growth was recorded 2 yr after planting without shrubs. The positive shrub
effect on seedling growth, especially marked in fenced areas, was more important
in Q. pyrenaica in the first growing period and in Q. ilex in the second; 2 yr
after planting no difference in shrub effect on growth was found in either Quercus
species. Seedling herbivory was a limitation to seedling growth in areas without
shrubs,mainly in the case of Q. pyrenaica.
Conclusions: In Mediterranean grazed areas with important summer drought
and very sandy soil, shrubby C. multiflorus plants have a clear facilitative effect
on seedlings of ecologically contrasted Quercus species. The facilitative effect was
found in both marcescent and sclerophyllous oak seedlings, but to a different
degree depending on the species considered and the variablemeasured (survival
or growth). In terms of survival, the marcescent species was more favoured by
shrub cover than the sclerophyllous one, and this effect was accentuated
through time. However, in terms of growth, although Q. pyrenaica was initially
more favoured by shrubs, differences between the two species were attenuated
after 2 yr. Therefore, C. multiflorus can have a key role in restoration of these oak
degraded environments.

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