Abstract: In this paper time series methods are applied to analyse seasonality，trends and periodicity of population density on 11 species of rodents in the Chihuahuan Desert of North Ameriea，and a seasonality．index is developed to evaluate the seasonality of population density as well．The results reveal that Chaetodipus penicillatus has the most significant seasonality，but two species in genus Peromygcus and Perognathus flavus have the most ambiguous seasonality of all, There are trends in population density of7 pecies．Popalation density of 6 species tends to increase，on the contrary that of Dipodomys spetctabilis trends to deerease during the study period．Weind out a 4-year period in fluctuation of population density of Dipodomys merriami，a 4．5-year period in Peromyscus maniculatus and a 1-year period in the other three species includingChaetodipus penicillatus, Reithrodontomys megalaotis and Onychomys leucogaster．A comparative study on seasonality，trends and periodicity shows that population dynamics 11 species varies widely and lacks clear and consistent patterns with their phyloge-netieal history．We suggest that it is diverse seasonality，trends and periodicity patterns that keep coexistence temporally in 11 species.

Key words: Coexistence, Dcsert, Periodielty, PopuIation density, Rodents, Seasonalit

摘要： 本文提出了季节性指标并用时间序列方法分析和比较了北美Chihuahuan荒漠11种动物种群密度的季节性、趋势和周期性。结果表明，研究期各年间盘尼西拉特斯颊囊鼠(C.p-enicillatus)有最显著的季节性，鹿鼠属(Peromysus)的两个物种和伏拉瓦斯囊鼠(Pg.flavus)节性最无规律，11个种群中有7个有趋势，除旗尾更格卢鼠(D．spectabKls)的种群密度呈减少趋势外，其余6个种群的密度呈增加的趋势1种群密度的周期，麦利阿姆更格卢鼠(D．merriam)是4年，曼利卡拉特斯鹿鼠(P．maniculatus)是4.5年，盘尼西拉特斯颊囊鼠(C．penicilatus)等3个种群是1年。对11个种群的比较说明，这些种群密度的季节性、趋势和周期性呈现出明显的多样化，且与它们的亲缘关系或种系发生历史无显著关系11个种群的密度变动的多样化维持了它们在时间的共存。

关键词: 共存, 荒漠, 周期性, 种群密度, 啮齿动物, 季节性