The study was conducted in Huantai County Shandong Province in North China to study the secondary succession of earthworm population under low and high soil fertility in agro-ecosystem. The result shows that seven species were found both in two agro-ecosystems, but the earthworm population density and composition are different, the average earthworm population in the high fertility soil is relatively abundance, the population density is 83.83 in./m~2. Among the seven earthworm species, Aporrectae trapezoids is the dominant species. While in the low fertility soil, the population density is 40.18 ind./m~2 and Drawida gisti is the dominant species. Comparing the density of each earthworm species in the two kinds of soil fertility agro-ecosystems, the density of Aporrectae trapezoids and Amynthas hupeiensis is significantly higher in the high fertility soil than that in the low fertility soil, while the difference of other five species is not obvious. This result shows that with the succession of the soil fertility, the earthworm also has a process of succession; the abundance species in the low fertility agro-ecosystem Drawida gisti is gradually substituted by Aporrectae trapezoids in the high fertility agro-ecosystem.
One-year experiment was also conducted to study the impact of the organic input on earthworm population and succession. The result shows that with the increase of the organic input, the earthworm population density is increasing, the earthworm density of the treatments has the following ascending trend: Chemical fertilizer