森林鼠类对秦岭南坡3种壳斗科植物种子扩散的影响

种子作为森林鼠类的主要食物来源,它们的扩散和更新很大程度上依赖于鼠类的传播。在鼠类扩散种子的过程中,种子特征和食物相对丰富度是影响鼠类对种子进行何种选择策略的重要因素。2011—2012年的8—12月,采用塑料片标记法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同域分布的3种壳斗科植物(锐齿槲栎Quercus aliena var.acuteserrata、栓皮栎Q.variabilis和短柄枹栎Q.serrata var.brevipetiolata)种子的扩散差异。结果表明:(1)鼠类倾向于贮藏营养价值较大的栓皮栎种子,并且其贮藏距离也最远(2011:1.52 m,2012:4.03 m),3种种子在食物相对丰富度较低年份被贮藏的距离均较远。(2)在食物相对丰富度较高的年份(2011),种子的消耗速率较慢,在种子释放10 d后种子释放点仍有67.33%的种子,贮藏量较高,至实验结束仍有29.67%的种子被贮藏。在食物相对丰富度较低的年份(2012),种子消耗速率较快,在种子释放后10 d内所有种子均被取食或搬离种子释放点,贮藏量较低,至实验结束仅有3.83%的种子仍被贮藏。(3)虽然栓皮栎种子的贮藏量最大,被贮藏后的存留量也最大,但其在实验地的分布却较小,说明种子扩散仅是植物分布与存活的第一步。以上结果表明,鼠类倾向于贮藏营养价值高的种子。在食物相对丰富度较高的年份会更多的贮藏种子,但种子被贮藏的距离较近,在食物相对丰富度较低的年份会更多的取食种子。

Seed dispersal of three sympatric oak species by forest rodents in the south slope of Qinling Mountains, China

Forest rodents, as seed predators and dispersers, play important roles in the regeneration of plants. Seed characteristics and food abundance influence the eating and hoarding strategies of rodents. In order to understand the seed selection differences by rodents, in 2011 and 2012 three sympatric Fagaceae plants (Quercus aliena var. acuteserrata, Q. variabilis and Q. serrata var. brevipetiolata) were used to study seed dispersal in Foping National Nature Reserve,located in the Qinling Mountains, China. Prior to the experiment, rodent density was surveyed from August to October of each year. Cage traps (27.0 cm×14.0 cm×14.0 cm), baited with peanuts, were set 10 m apart along two transects in each plot and were deployed from 17:00 to 17:30 daily. Traps were checked after 14 hours and all captured rodents were processed and immediately released. The seed mast was also surveyed from mid-August to late November of each year. 36 collection boxes were set up under 36 trees (12 trees of each species). The collection boxes were approximately 1 m² and were monitored every 7 days. Physical properties of the collected seeds were measured by technicians in the lab and chemical properties were determined by the Center of Grain Quality at the Ministry of Agriculture, China. Seed dispersal was surveyed in a deciduous broadleaved forest each year. Ten sites (1 m×1 m) were established as seed stations with a minimum distance of 15 m from one another. 20 tagged seeds of each of each of the three tree species (n=60) were placed at each station. Seed counts at each box occurred on days 1, 3, 5, 10, 17, 27 and 50 following presentation. Missing seeds were located by visual search and their fates followed. The results showed that: (1) rodents preferred to cache Q. variabilis seeds (with higher energy) at a greater distance, and eat Q. serrata var. brevipetiolata (with lower energy) in situ. Q. variabilis were cached farther than Q. variabilis (2011:1.52 m,2012:4.03 m). All three seed types were cached further when food was scarce. (2) In a mast seeding year (2011), rodents consumed seeds slowly and cached more seeds. 67.33% seeds remained at each station on the 10^th day, and 29.67% seeds remained in caches on the 50^th day. In the year that food resources were relatively poor, rodents tended to eat more seeds. All seeds were removed by the 10^th day and only 3.83% seeds remained in the caches on the 50^th day. When food was most scarce, all three kinds of seeds were cached less. (3) Although more Q. variabilis seeds cached by rodents survived in later experiments, it had a narrow range of distribution. This phenomenon indicates that seed dispersal is just the first step of plant distribution and survival. These results indicate that rodents primarily select seeds of high nutritional value to cache. More seeds were cached in the year with abundant food resources and at closer cache distances, while more seeds were consumed when food resources were relatively poor.