昆虫种子捕食与蒙古栎种子产量和种子大小的关系

Insect seed predation and its relationships with seed crop and seed size of Quercus mongolica

为了了解昆虫种子捕食者在栎类种群更新中的作用,于2006年秋季,在黑龙江省伊春市带岭区东方红林场研究了昆虫对蒙古栎Quercus mongolica在参园和东山两个种群的种子蛀食情况及其与蒙古栎种子产量和种子大小的关系。结果表明:(1)在参园和东山两个林分内,蒙古栎种子雨动态非常相似,种子雨成分中完好种子的平均密度仅为3.2±4.1个/m2(参园)和1.7±2.8个/m2(东山),分别仅占种子产量的4.0%和3.2%,而虫蛀种子和败育种子的比例均在38%以上,以虫蛀种子的比例最高,分别为58.2%和57.7%;(2)柞栎象Curculio arakawai是蛀食蒙古栎种子的主要昆虫种类,在虫蛀种子中所占比例高达96.8%(参园)和97.1%(东山),且象甲蛀食种子中所含虫卵数与种子大小有关,即种子越大,所含象甲的虫卵数就较多。本研究的结果说明2006年蒙古栎成熟种子多遭遇虫蛀,导致完好种子的数量极低,因而可能成为限制蒙古栎种群更新的重要因素。

In autumn of 2006, insect seed predation and its relationship with seed crop and seed size of Quercus mongolica were investigated at Cenyuan and Dongshan sites in Dongfanghong Forest Farm in Dailing Region of Yichun City, Heilongjiang Province, Northeast China. The dynamics of seed rain and its composition of Q. mongolica were similar between the two sampled sites, though seed crops varied between both sites partly due to tree size based on diameter of breast height. For individual tree sampled, sound acorns had a very low density at both sites： 3.2 ± 4.1 nuts/m^2 （Cenyuan） and 1.7 ± 2.8 nuts/m^2 （Dongshan）, same with the proportion of sound acorns at both sites, only 4.0% （Cenyuan） and 3.2% （Dongshan） of the total seed crops, but the proportions of both insect-infested and aborted acorns were very high, over 38 % at both sites. In particular, the proportion of insect-infested acorns was up to 58.2% （Cenyuan） and 57.7%（Dongshan）. Weevil Curculio arakawai was the key insect species infesting Q. mongolica acorns with up to 96.8 % （Cenyuan） and 97.1% （Dongshan） of insect-infested acorns sampled. We also found that the number of weevil eggs and larvae in each weevil-infested acorn was significantly correlated with acorn size, i.e. larger acorns had more weevil eggs and larvae. These results indicated that seed crops of Q. mongolica were very poor in 2006, with most mature acorns infested by insects （especially by weevils） and fewer sound acorns available for dispersal and subsequent seedling recruitment. Thus, intense insect seed predation may be one primary limiting factor influencing population regeneration of Q. mongolica especially in seed-poor years.