啮齿动物对不同林木种子的搬运和取食微生境选择机制

不同植物种子依靠不同的方式实现扩散,啮齿动物对林木种子搬运后在取食点微生境和贮藏方式的选择存在偏好,研究其贮藏行为与微生境的关系是探究幼苗建成的关键。在秦岭中段火地塘林区,采用标签标记法,以锐齿槲栎、华山松和油松种子为材料,探究了小型啮齿动物对松栎混交林建群种种子扩散过程的影响。结果表明:1)油松种子原地取食率显著高于锐齿槲栎和华山松种子,且啮齿动物更倾向于搬运后取食(60%)和埋藏(4.33%)华山松种子,搬运后取食距离也为华山松最大(2.49 m);锐齿槲栎小种子被搬运后埋藏的距离最大(4.92 m)。2)除华山松种子外,其他类型种子被搬运后单个取食的比例均在85%以上;油松种子不存在埋藏点,而其他类型种子90%以上均以单个形式被埋藏。3)大部分种子被啮齿动物搬运后选择在裸地丢弃;锐齿槲栎大种子(87.5%)、小种子(78.57%)和华山松种子(53.33%)较大比例被啮齿动物埋藏在灌丛下方,埋藏在裸地的种子较少。4)大部分种子在灌丛下方被取食,仅华山松种子被啮齿动物搬运到洞穴取食;除油松种子被大量原地取食外,其他类型种子被搬运到取食点的种子比例基本呈现由微生境植被复杂到简单(灌丛—草丛—灌丛边缘—裸地)而逐渐减小的趋势。种子的营养价值及取食和搬运过程中啮齿动物付出的成本是影响种子命运的关键性因子,且啮齿动物对种子埋藏和取食地点的微生境存在较明显的选择性。

Selection mechanism of rodents on the removal and predation microhabitats of seeds from different tree species

Different types of seeds could be dispersed in various ways. Rodents show a significant preference in the microhabitats of predation sites and caching methods after seeds removal. Understanding the relationship between storing behavior and microhabitat is the key to study seedling establishment. The objective of this study was to reveal the effects of small rodents on seed dispersal patterns of constructive species in pine-oak mixed forests. Field experiments were conducted in the Huoditang forest region in the middle of the Qinling Mountains, Shaanxi Province, northwestern China. Coded plastic tags were used to study the seed fates of Quercus aliena var. acuteserrata, Pinus tabuliformis, and Pinus armandii. The results showed that the in situ seed predation rate of P. tabuliformis seeds was significantly higher than the seeds of the other three types of seeds. P. armandii seeds had the highest predation rate (60%) and cache rate (4.33%) after removal by rodents, and the longest average dispersal distance of predation sites (2.49 m). The small acorns of Q. aliena var. acuteserrata had the longest dispersal distance of cache sites after removal by rodents (4.92 m). All types of seeds except P. armandii seeds had over 85% of the sites were used as predation sites. P. tabuliformis seeds had no cache sites. Over 90% of the cache sites of the other three types of seeds contained a single seed. Most of the seeds were discarded after removal by rodents. The proportions of seeds that were cached under shrubs were higher for large and small acorns of Q. aliena var. acuteserrata and P. armandii seeds, which were 87.5%, 78.57% and 53.33% of the total number of seeds after cache by rodents, respectively. A lower proportion of seeds was cached on bare land. Most of seeds were eaten under shrubs. Only P. armandii seeds were eaten in the holes after removal by rodents. A higher proportion of P. tabuliformis seeds were eaten in situ than the other three types of seeds. Except P. tabuliformis seeds, the predation rates for the other three types of seeds tended to decrease along microhabitat changing from simple to complex (shrub to grass to shrub edge to bare land). The nutritive value of the seeds and the cost of the rodents'' predation and removal process were the key factors affecting the fates of seeds, and rodents showed obvious preference in the microhabitats of seed storage and predation sites.