啮齿类取食的物种偏好与时空格局

通过强烈消耗土壤种子库，动物取食种子对植物种群更新和群落动态产生深远的影响。一般认为种子被食概率的空间格局取决于种子密度和离母树的距离，而环境（如地形）异质性的影响则一直没有得到足够的关注，与此相关的机制及其影响程度亦不清楚。研究设计在野外埋放种子以模拟种子扩散后的情形，监测啮齿类对种子的取食，以检验种子取食受埋藏生境、时间及动物对种子种类的偏好等因素的影响。结果表明，经过1a实验，8种落叶阔叶树种子的累计取食概率为0～48．25％，平均值为20％；山顶部位的取食概率大致是其它部位概率的3倍；埋放在凋落物层中的种子被食概率大约为埋放在土壤层中概率的2倍。利用logistic回归模型进行统计分析表明，种子被食概率变化的45％可以被上述因素解释。其中，物种偏好是影响种子被取食概率的首要因素，其后依次是地形、埋藏时间和深度。啮齿类明显喜好较大的种子；其取食行为在山脊部位明显较其它部位更频繁和剧烈；对埋藏种子的取食从3月份开始加剧，到7月份以后平息下来。种子埋放深度对啮齿类的取食概率有显著影响。

Species preference and spatiotemporal patterns of predation by rodents

By intensive consuming on soil seed bank, the post-dispersal seed predation has prominent impacts on population regeneration and the dynamics of plant community. The spatial variation of seed predation intensity has been generally linked with density and distance to the parent trees in modeling, while the impacts of environmental variations (e.g. topography) have received much less attention, the related contributions and mechanisms are still open. We buried seeds in the field, mimicing the post-dispersal condition, and monitored the seed predation by rodents, in order to test the effects of species preference, topography, time and depth of burial on the probability of predation. In a one year experiment, the cumulated average seed predation is 20%, range from 0 to 48.25% among eight deciduous tree species, the final probability of seed predation at hilltop is about 3 times as those at other topographic positions; the predation probability occurred to the seeds buried in plant litter layer were twice as those buried in soil. The interactions between the factors were analyzed, and a logistic regression model was fitted to estimate their contribution to the variation of seed predation probability. In result, about 45% of variation can be explained by the factors considered. In summary, species preference is a primary factor for the variation of predation, followed by topography, time and burial depth in contributions. Rodents significantly favor the species with larger seeds; their foraging activity seems to be much more intensive or frequent at ridge than other slope positions. Seed predation becomes more intensive since March, and turns down after July. The depth of burial has prominent effect on the efficiency of seed search by rodents.