秦岭南北坡森林鼠类对板栗和锐齿栎种子扩散的影响

森林鼠类的种子贮藏行为对植物的扩散及更新会产生积极的影响。2012和2013年秋季,分别在秦岭北坡的周至国家级自然保护区和南坡的佛坪国家级自然保护区内,调查了森林鼠类对板栗(Castanea mollissima)和锐齿栎(Quercus aliena)种子的取食和扩散差异。结果显示:1)秦岭南北坡的环境因素,特别是植被因素,对鼠类扩散板栗和锐齿栎种子具有重要的影响。南坡较为丰富的壳斗科植被种类,导致2种种子在南坡存留时间均长于北坡,而北坡的扩散取食和丢失率均高于南坡。2)种子特征影响鼠类的取食或贮藏偏好。由于较高的蛋白、脂肪等营养含量,鼠类更喜好取食或搬运贮藏板栗种子。然而,低营养但高丹宁含量的锐齿栎种子仍然被鼠类大量贮藏。3)2种种子在南北坡的扩散历程在两个年份间有很大差异,在食物相对匮乏的年份(2012年),种子被扩散的速度更快且丢失的比率更高。这种差异反映了种子大小年现象对森林鼠类取食和贮藏策略的影响。4)无论在秦岭南坡还是北坡,营养价值含量(如蛋白和脂肪)较高的板栗种子的取食和贮藏距离都明显大于营养价值含量较低的锐齿栎种子,这与最优贮藏空间分布模型的预测一致。

Effect of forest rodents on predation and dispersal of Castanea mollissima and Quercus aliena seeds on south- and north-facing slopes of Qinling Mountains

Scatter hoarding behavior of forest rodents has a positive effect on plant distribution and regeneration. Environmental factors, seed traits, and food abundance can affect the hoarding strategy of forest rodents. However, current research in this area has not been sufficiently comprehensive and little information is available on how major environmental factors, such as climate zone district, can affect seed dispersal by rodents. Predation and dispersal of Castanea mollissima and Quercus aliena seeds were investigated at the Zhouzhi National Nature Reserve on the north-facing slope of Qinling Mountains and at the Foping National Nature Reserve on the south-facing slope of Qinling Mountains in October 2012 and October 2013. Ten plots (1 m × 1 m), separated by a 15-m long transect line, were established as acorn stations in a deciduous broad-leaved forest. Twenty C. mollissima seeds and 20 Q. aliena seeds were placed at each station and seed fates were monitored at 7 d after initial release. During each visit, we searched the area around each station (radius <30m) for seeds that removed by rodents and recorded acorn fates. Environmental factors, especially vegetation, have a significant impact on seed dispersal. Because of Fagaceae abundance, the lifetime of seeds from both study species was longer on the south-facing slope than on the north-facing slope, while the feeding and loss rate of seeds from both species was higher on the north-facing slope than on the south-facing slope. Seed traits affected the eating and hoarding preference of rodents. Rodents preferred seeds of C. mollissima, due to their higher nutritional content, such as fat and protein than those of Q. aliena with low nutritional and high tannin content. The differences in the dispersal process of seeds from both study species were significant between the north- and south-facing slopes over the 2 years of study. In 2012, a year of food shortage, the distribution and loss rate was higher than that in 2013, which indicated that the eating and hoarding strategy of rodents might be affected by food abundance. Rodents preferred eating and hoarding seeds with low nutritional value (low protein and fat content) in short distance and those with high nutritional value (high protein and fat content) in long distance on both the north and south-facing slopes, results that supported the Optimal Cache Spacing Model. This study indicated that the dispersal process of seeds from both study species on the north and south-facing slopes of Qinling Mountains was different. Vegetation factors, seed traits, and food abundance affected the selection strategy of forest rodents. Forest rodents could identify different seeds and selectively consume them, a factor that might influence the dispersal and natural regeneration of C. mollissima and Q. aliena seeds.