Seed shadow of Quercus liaotungensis in a broad-leaved forest in Dongling Mountain

The seed shadow of oak (Quercus liaotungensis Koidz.) was investigated in a broad-leaved deciduous forest in Dongling Mountain in 1997. The seed rain patterns under oak tree crown for three out of four oak trees fit quadratic distribution, with high coefficients of determination. For each of the four trees selected in tills study the seed rain size estimated from the viable acorns collected from the traps deployed under the crown was low, ranging from 26 to 259. For each of the four oak trees, the average density of the seed rain under oak tree crown ranged from 0.76 to 7.26 seeds/m(2). The average seed rain density estimated from the acorns in the traps deployed randomly in the field was 1.57 seeds/m(2). After all viable acorns fell, the acorn ground density estimated from the acorns in the quadrats was 0.13 seeds/m(2), but no viable acorns were found on the ground under the tree crown of the four oak trees, although the area under die crown was over 5 folds than the area of the combined quadrats. These results indicated that a large number of acorns was removed or predated by vertebrates once the acorns fell on the ground and acorns predation was more intensive in the sites directly under the parent trees than the sites away from the parent trees; this supports the distance-dependent hypothesis. Of the total acorns of all four oak trees, the viable acorns only accounted for 18.1%, and 17.8% for acorns infected by insect larvae, 12.1% for immature acorns, 3.6% for decayed acorns, and the acorns predated by rodent directly in the crown was the highest, accounting for 48.4%. The proportion of acorns predated by animals including vertebrates and invertebrates amounts up to 78.3%, indicating that acorn predation by animals is a limiting factor affecting acorn survival before seed dispersal. The sustained time of viable acorn fall ranged from September 8 to October 3 for the four oak trees, with the peak between 16th and 26th September, The number of acorns was not significantly different among the four directions around the trunk base.