中文摘要：

针对洞庭湖区实施的＂退田还湖＂重大生态环境恢复工程,以原有＂围湖＂造的垸田和垸外湖滩为对照,对退田还湖区（含双退与单退两种形式）的啮齿动物群落于2003～2006年进行定位观察。采用夹捕法进行采样,于每年的1月、4月、7月、10月进行。比较洞庭湖不同退田还湖类型区东方田鼠和黑线姬鼠种群的繁殖指标参数。总体来看,调查期间东方田鼠和黑线姬鼠的繁殖指数要比上世纪80～90年代报道的要高,这与前几年其种群处于年数量低谷有关,是东方田鼠和黑线姬鼠种群负反馈机制的体现。不同类型生境间的比较结果显示,单退垸与原有生境没有明显变化,而双退垸内黑线姬鼠和东方田鼠均有较显著的变化,主要表现在双退垸内夏季东方田鼠保持高的繁殖能力和黑线姬鼠的繁殖力锐减。由于双退垸的高程优势,鼠群在夏季汛期不会迁出垸内,仅迁移集中至较高区域,这种水位变化引导的害鼠种群迁移应该是造成繁殖变化的主要原因。由于黑线姬鼠不适应这种迁移以及集中后与东方田鼠的激烈竞争,迁移到高地后的黑线姬鼠几乎停止繁殖,繁殖指数仅为0.03（I♀=0.05）,明显低于当期其它生境。值得注意的是夏季滞留在双退垸内的东方田鼠,繁殖强度却不减,繁殖指数达1.54（I♀=3.36）,与春季湖滩种群的相当。说明没有经过长距离迁移的东方田鼠种群,在夏季仍会保持较高的繁殖强度,与夏季被迫远距离迁入农田的东方田鼠种群繁殖力急剧下降形成鲜明对比。由此可知,在初夏如果有适宜的栖息地（如双退垸的高台、原有堤岸等）,东方田鼠仍能保持较强繁殖力。本文揭示了双退垸内水位变化引发种群迁移后东方田鼠和黑线姬鼠繁殖能力的这种迥异表现,具体深层次原因有待进一步探讨。

英文摘要：

The reproductive characteristics of the striped field mouse （ Apodemus agrariuz ） and the Yangtze vole （ Microtus fortis） were studied in an area being restored to lake in the Dongting Lake region. There were two main ways that farmland was restored. In Double Restoration Polders （DRP） both human habitation and agricultural activity were removed, while in Single Restoration Polders （SRP） only human habitations were removed but agricultural activities continued. The study was conducted in January, April, July and October from 2003 to 2006. Snap traps were used to get samples in all plots throughout the census. Seven typical plots （ seven different types of habitats for small mammals） were selected for investigation. Habitat 1 was hilly woodland around the lake which was covered by some shrub, arbor and herb, and M. fortis often immigrated to here from beach of lake during flood season. Habitat 2 and habitat 3 were normal farmland in protected polders. There was an M. fortis population migrating into habitat 3 during flood season, as there was a large stretch of beach outside of the dike near the habitat. Habitats 4 and 5 were SRP. Habitat 4 was still farm and the majority of the area of habitat 5 was planted in one kind of poplar （ Populus spp. ）. Habitat 6 was typical DRP, which was also covered by arbor. Habitat 7 was the beach of lake which has fully developed （ matured beach） , it was covered by Carex spp. and Polygonum hydropiper. The reproductive characteristics of Apodemus agrarius and Microtus fortis were compared among these habitats, and also compared with historical data we acquired during 1980 and 1990. The indices of reproduction of females were higher than those in the historical data for both A. agrarius, which was the dominant species in farmland, and for M. fortis, which was dominant species on beach of the lake. Both species were at a low point of multi-annual population fluctuations. Both species displayed no significant changes except for in DRP during the summer. In