Tree growing space and acorn production of Quercus robur

Pedunculate oak (Quercus robur L.) is considered the main commercial tree species in conditions of floodplain forests of central Europe. In the Czech Republic clear-cutting silvicultural system represents a prevailing regeneration method of oak stands in floodplain forest. The natural regeneration is limited only in stands and years with sufficient acorn production. We analysed an acorn crop periodicity and an influence of canopy opening to the acorn production in South Moravian floodplain forest, Czech Republic between 2008 and 2011, The acorn crop from trees with different growth spaces in four stand conditions (closed canopy (A), moderate open canopy (B), open canopy (C) and single growing trees (D) with unlimited growth space was analysed. The amount of acorns was determined using seed traps placed under the crowns of sample trees. The average amount of acorns in 2009 and 2011 ranged from 13 (A) to 102 (C)/m2 and from 2 (A) to 124 (D)/m2, respectively. At the same time, a considerable difference was recorded in the fructification of sample trees in the various stand situations. Significant correlations were confirmed between the amount of acorns and crown size (r2 2009=0.27, r2 2011=0.07) of parent trees and their growth space – release area (r2 2009=0.42, r2 2011=0.25) and social area (r2 2009=0.31, r2 2011=0.26). The production of acorns could be affected by establishing conditions for the pedunculate oak with a minimum crown projection area in adult trees of at least 70 m2 and/or with a minimum release area of 300 m2, it means spacing between parent trees about 10 m or 100 trees per 1 ha.