川西平原农田啮齿动物群落动态：趋势和周期性

本用时间序列分析方法，对川西平原农田由8种啮齿动物组成的生物量、物种多样性的Shannon指数和Simpson指数中3个主要群落变量的趋势和周期性进行了分析和比较!结果表明：(1)3个变量都有增加的趋势．生物量是二次抛物线，Shannon指数是指数函数，Simpson指数是正弦函数。(2)3个变量中生物量显示出了周期性，这个变量的周期都约为1年。1年的周期与四川亚热带农业生态系统初级生产力的动态相一致：Shannon指数和Simpson指数末显示出周期性—川西平原啮齿动物群落3个变量的增加趋势，可能是农业生态系统中啮齿动物与人类长期共存所形成的适应特征，它们能随农业产量增加这样的环境变化使各个群落变量呈现出增加的趋势；也可能不过是处于群落自然波动中的上升阶段、因此需要长时间的研究工作，才能判断该增加趋势的生态学本质。

Dynamics of the Rodent Community in Cropland of the Western Sichuan Plain: Trends and Periodicity

The time series analysis method was applied to character the trends and periodicity of the 3 variables of a 8-species rodent community in the Western Sichuan Plain, including biomass, Shannon index and Simpson index. Results suggest that: (1) Fluctuations of the 3 variables all showed increasing trends. The trend of biomass is parabola function, Shannon index and Simpson index are exponential and sine functional respectively,and (2) biomass showed one-year periodicity. The annual periodicity of the variable is synchronized with growth and harvest of rice-wheat, rice-rape, or maize-sweet-potato in subtropical agriculture ecosystem in Sichuan. The above adaptive traits resulting from coexistence of rodents and people probably make the rodents respond to cultivation quickly, such as environmental changes like yield increasing, so that increasing trends of 3 community variables were observed. Or the 3 community variables may be increased during the increasing period of their natural fluctuations. In order to characterize ecologically we need long-term study of the community.