秦岭森林鼠类对华山松种子捕食及其扩散的影响

森林鼠类的种子贮藏行为对植物的扩散和自然更新有着非常重要的影响。通过塑料片标记法,2008和2009年的9月—11月分别在秦岭南坡的佛坪国家级自然保护区内调查了森林鼠类对华山松(Pinus armandii)种子的捕食和扩散,结果显示:森林鼠类对华山松种子有着非常大的捕食压力。在2008年,几乎所有的种子(96.4%)在第3天后就被全部取食,而在2009年,也有将近一半的种子(49.6%)在第3天后被取食。但与此同时,鼠类对华山松种子的扩散也起着非常重要的作用。尤其在2009年,第3天时鼠类最高分散贮藏了17.75%的种子,而且直到第19天后仍然有12.25%被贮藏的种子存活下来。华山松种子在两个年份间的扩散历程有很大差异。在2008年,几乎所有的种子都被鼠类取食,贮藏量非常小;而在2009年,种子被贮藏的比例显著的增加。这个结果可能与种子大小年现象有着十分紧密的联系。2008年是华山松种子的小年,产量非常低。鼠类为了满足其日常的能量需求,只能大量的取食有限的种子,而减少其贮藏量。而2009年是华山松种子的大年,产量非常高。鼠类在满足其日常能量需求的同时,还有大量剩余的种子供其贮藏。

Effect of forest rodents on predation and dispersal of Pinus armandii seeds in Qinling Mountains

Seed dispersal is recognized as a key phase affecting plant regeneration and distribution. By acting as seed dispersal vectors, forest rodents play an essential role in this phase through their scatter hoarding behavior. Although rodents can consume a large number of seeds to meet their immediate energy requirements, they also store some seeds in scatter caches for future use to ensure overwinter survival or reproductive success. Buried seeds are more likely to germinate and survive to the seedling stage if the animal fails to recover some of the seeds; this may occur if, for instance, the animal has died or moved, or stored more than it could use. Pinus armandii, which are common and often dominant tree species in many temperate and subtropical forests, are an important food source for many wild animals. Much attention has been paid to the dispersal biology of Pinus spp.; however, knowledge of the interactions between P. armandii seeds and rodents in Qinling Mountains is still poor. The predation and dispersal of P. armandii seeds by forest rodents were investigated using plastic tags in Foping National Nature Reserve (35°0'N, 105°30'E), located in the southern aspect of Qinling Mountains in Shaanxi Province during September-November of 2008 and 2009. Approximately 20 plots (1 m × 1 m), separated by 15 m along a transect line, were established as seed stations in a deciduous broad-leaved forest. In September of each year, 50 tagged seeds were placed at each station and seed fates were monitored on 1, 2, 3, 11 and 19 days after initial placement. During each visit, we searched the area around each station (radius < 30 m) for seeds removed by rodents and recorded their fates. The results showed that rodents imposed a strong predation pressure on P. armandii seeds in this study site. In 2008, nearly all the seeds (96.4%) were consumed by the third day, and almost half of the seeds (49.6%) were consumed by the third day in 2009. Rodents also played an important role in seed dispersal of P. armandii. In 2009, rodents scatter hoarded 17.75% seeds by the third day and 12.25% of hoarded seeds were still alive by day 19. There was a significant difference in seed dispersal of P. armandii between the two years. In 2008, almost all the seeds were consumed by rodents and the quantity of cached seeds was very small. The proportion of cached seeds was significantly greater in 2009 than in 2008. This result may be associated with mast seeding. The yield of P. armandii seeds was very low in 2008 and rodents had to consume a large number of seeds to meet their daily energy needs, leading to a reduction in storage. Whereas the yield of P. armandii seeds was very high in 2009, and there were sufficient seeds to not only meet the daily energy needs of rodents but also to hoard seeds for future use.