Factors Affecting the Natural Regeneration of Sessile Oak (Quercus Petraea) in North Wales: II. Acorn Losses and Germination Under Field Conditions

Shaw, M

Previous investigations at Coed Cymerau National Nature Reserve, Merionethshire have shown that the production and viability of acorns are unlikely to be limiting factors in the natural regeneration of this woodland (Shaw 1968). By contrast, only a small proportion of the acorns produced survive long enough to become seedlings. A few acorns are removed from the trees prior to fall but the main losses occur when the acorns reach the ground, the conversion rates being 0+6% and 1+5% for 1964-65 and 1965-66 respectively. Acorn predators such as wood pigeons (Columba palumbus L.) and small mammals were thought to be largely responsible for such low values. The present paper deals with what happens to acorns on the ground, using experimental plantings as opposed to naturally fallen acorns. Acorns which reach the ground can fail to produce seedlings for four main reasons. (a) They are non-viable when they leave the tree. (b) They are eaten during the 7-8 months period between fall and the completion of germination (c) They fail to reach a position on the ground in which the conditions necessary for germination exist. (d) They subsequently lose the capacity to germinate (or complete germination) as a result of factors such as insect or fungal attack, freezing, drying or even excessive moisture. Previous investigations have shown that (a) is not a major factor but that (b) probably is. Little is known about the germination requirements of acorns in the field (c) but Watt (1919) found suitable conditions were often lacking in southern oakwoods. The range and complexity of factors involved in (d) would require a much more detailed approach and the present investigation concentrated on (a), (b) and (c).

Factors Affecting the Natural Regeneration of Sessile Oak (Quercus Petraea) in North Wales: II. Acorn Losses and Germination Under Field Conditions

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