Abstract: This study determines the effects of nutrition，predation，and spacing behaviour interactions on the population demography of root voles，Microtus oeconomus，using a iactorial experiment design under enelosures in field．The effect patterns of food availability and predation on the population dynamics of the voles reported in this paper is the first part of the muhifaetorial hypothesis of population system regulation for small rodents.The specific hypothesis tested is that the availability of high-quality food and predation act independently and additively to limit the population densities Qf small rodents．
The results from four experimental treatments generally suppotted the hypothesis that food availability and predation have independent and additive effects on the vole populations．The predictions that the populations with supplemental food and no predation would reach the highest densities，those with no supplemental food and predator access (control)show the lowest densities，and those with single treatment have intermediate densities have been confirmed.A two—way AN0VA indicated that both food and predation treatments had significant effects on densities during 1— 20W K ．Prevention of predator accessing significantly affected the recruitments during 4— 20W K，but the effects of additional food on recruitments was somewhat less and only marginally signlficant．
The effects of both food and predation treatments on the densities and recruitments appeared to be additive (no significant interaction)and different in magnitude.Also as expected the patterns of recruitment and the instantaneous rate of population increase under four different treatments paralleled the observed density patterns．

Key words: Small rodents, Population system, Muhifaetorial hypothesis, Food availability, Predation, Root voles, Population dynamics

摘要： 本研究在野外围栏条件下采用析因实验设计，测定营养、捕食及空间行为对根田鼠(Microtus oeconomus)种群统计特征的影响。本文旨在检验下述特定假设：高质量食物可利用性和捕食对限制小型啮齿动物种群密度具有独立的和累加的效应。
3年期间，4种野外实验处理6个重复的研究结果表明，附加食物并预防捕食者处理的种群具有最高密度；未附加食物及不预防捕食者处理(对照)的种群密度最低；而单一处理的种群其密度居中。不同处理条件下。新生个体在种群的补充模式以及种群瞬时增长率的变化均与种群密度的变动相应一致。
双因素ANOVA的结果证明，附加高质量食物能明显地提高根田鼠的种群密度，而对种群补充量的作用则较弱，仅接近显著水平；预防捕食者不仅能显著地作用于种群密度，更能强烈地影响种群补充量。高质量食物和捕食者的作用具有累加的性质，两者的交互作用对种群密度和补充量均无显著影响。

关键词: 小型啮齿动物, 种群系统, 复合因子理论, 食物可食用性, 捕食, 根田鼠, 种群动态