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551.
552.
Spatial patterns of seedling regeneration of woody Mediterranean plants are widely documented, with seedlings and juveniles
growing almost exclusively under shrub and tree canopy. Neighbourhood habitat amelioration and consequent facilitative effects
on recruitment have been extensively suggested as the major determinant of such spatial pattern for Mediterranean vegetation.
Much less is known on recruitment patterns of perennial herbs. As herbs differ from woody plants in many relevant ecological
aspects and in their life cycles, we would expect particularities in their recruitment dynamics. We analysed the spatial (regional,
local and fine-scale) variation in environment (herb cover, litter depth, air temperature and irradiance) and its relationship
with seedling emergence, mortality, and recruitment of the perennial herb Helleborus foetidus (Ranunculaceae) during 2 years. We conducted the study in three distant localities in south-eastern Iberian Peninsula (defining
the regional scale). Local scale was defined in terms of microhabitat type based on three categories of vegetation cover (under
evergreen shrubs or trees, under deciduous spiny-shrubs, and in open interspaces). Finally, fine-scale variation was defined
in terms of 1 m2 sampling plots. Our results showed regional, local and fine-scale variations in recruitment, with the major source of variation
changing across scales. Seed input was important in determining differences in recruitment both at the largest (regional)
and the finest scale. Environment had minor importance in shaping differences in recruitment at these two scales. At the local
scale, variation between microhabitats was mainly related to differences in seedling survival through facilitative effects
(alleviation of water and irradiance stresses) of shrub and tree cover, although such facilitative effect was not consistent
in all localities or years. Our study thus points to a similarity in the spatial patterns of recruitment (and in the environmental
factors shaping such patterns) between Mediterranean woody plants and perennial herbs, but much more effort is needed to assess
the generality of such similarity. 相似文献
553.