【摘要】 在北京东灵山地区的一个落叶阔叶林中调查了辽东栎 (QuercusliaotungensisKoidz.)的种子雨。对于选定的4棵辽东栎中的 3棵 ,树冠下的种子雨分布格局符合二次分布 ,具有很高的决定系数。由设置在树冠下的种子捕捉器收集的坚果数量来估计整棵树的种子雨。 4棵树的种子雨中有活力的种子很少 ,变化范围从 2 6到 2 5 9个。每棵树的树冠下的种子雨密度变化范围从 0 .76到 7.2 6个 /m2 。林中平均种子雨密度由随机设置在林中的 47个种子捕捉器估计 ,平均种子密度为 1.5 7个 /m2 。当所有树上的坚果落完后 ,由在地表随机设置的小样方中的坚果数量估计的地表的种子密度为 0 .13个·m2 。但是在树冠下面的地表上没有发现有活力的种子。这说明一旦辽东栎的坚果落下后 ,大量的坚果被动物捕食和搬运 ,并且树冠下的坚果捕食更为强烈 ,这支持距离制约假说 (distance_dependenthy pothesis)。合并 4棵树的种子雨数量 ,有活力的种子只占 18.1%,被昆虫幼虫侵害的占 17.8%,不成熟的占 12 .1%,腐烂的占 3.6 %,被动物在树冠直接捕食所占比例最高 ,为 48.4%。脊椎动物和无脊椎动物合计捕食占 78.3%。这说明动物对坚果的捕食是影响坚果存活的主要因子。坚果的下落时间从 9月 8日到 10月 3日 ,下落高峰期从 9月16日到 2 6日。更多还原

【Abstract】 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 this 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 the 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.更多还原