Abstract
Few studies have determined the influence of acorn size on germination and predation percentage at tree level. To evaluate the seed size influence at individual tree level, trees producing two different sizes of acorn were chosen. Our results show that smaller acorns were significantly more infested (49.6–75.3%) than larger ones (11.0–27.33%). About germination, big acorns achieved the best germination percentage compared to the smaller ones (18% in infested and 76% in sound acorns for the small acorn group versus 69.3% in infested and 93.3% in sound acorns belonging to the big acorn group). We also found that there was a difference in behaviour between big and small seeds at tree level. The same size belonging to different functional groups presented a difference at the behavioural level per tree. Infested small acorns from trees 8 and 10 had only 33 and 13% germination, while big acorns from trees 2, 3, and 6 (there was no difference between both sizes) presented 67, 97, and 83%, respectively. These results indicate that the production of acorns with two different sizes could be a strategy for species regeneration, producing each size for a different purpose.
Highlights
Quercus L. is a genus that produces a great acorn-size variation within the species and even at the individual tree level
Big acorns achieved the best germination percentage compared to the smaller ones (18% in infested and 76% in sound acorns for the small acorn group versus 69.3% in infested and 93.3% in sound acorns belonging to the big acorn group)
In accordance with previously published work, which aimed to determine the reproductive behaviour of cork oak [18], we proposed to understand the reason that this species produces different acorn sizes at the individual tree level
Summary
Quercus L. is a genus that produces a great acorn-size variation within the species and even at the individual tree level. Female flowering, or both may happen in spring and again in autumn [1,2,3] Most of these species need only one season to complete the cycle (from flower until seed maturity) whereas others require two years. Several trees produce biennial acorns with anthesis in spring or autumn of the first year and fruit set in the second year All of this could be the origin of acorn size variability because spring flowering has more time to grow than autumn ones in annual cycle. The biennial flowering has more time than annual ones All of these reasons make cork oak a very interesting species that produces acorn from September to January with different sizes and different origins
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