Abstract: To elucidate the effects of varying land-use types on the spatial distribution of earthworm ecological groups in a typical organic farm in Shunyi, Beijing, we investigated the distribution characteristics of earthworm populations across four land use types (vegetable fields, woodlands, orchards, and grasslands). We further analyzed the effects of different earthworm ecological groups on soil physicochemical properties through their casts. The results showed that the earthworm densities per unit area across land use types were 57 individuals·m^-2 in orchards, 54 individuals·m^-2 in vegetable fields, 37 individuals·m^-2 in woodlands, and 19 individuals·m^-2 in grasslands. Land use type significantly influenced the distribution of earthworm ecological groups. Vegetable fields and grasslands were dominated by endogeic earthworms (Amynthas hupeiensis), accounting for 46.30% and 47.00%, respectively. Orchards and woodlands were dominated by anecic earthworms (Amynthas carnosus, Metaphire tschiliensis), with proportions of 52.60% and 43.24%, respectively. Epigeic earthworms (Drawida japonica, Drawida gisti gisti) did not exhibit dominance in any of the four land-use types. Soil organic matter, nitrogen, phosphorus content, and human disturbance were the main factors shaping the distribution of earthworm ecological groups. In woodlands, the three ecological groups of earthworms exhibited a more balanced distribution than in the other three land use types, with clear ecological niche separation. Earthworm casts had the greatest effect on woodland soil properties, increasing cation exchange capacity, total nitrogen, and soil organic matter by 19.79%, 154.43%, and 373.14%, respectively (P≤0.05). Endogeic earthworms exerted the strongest influence on the formation of large soil aggregates (d>2 mm), with their effects on soil properties being higher than those of the other ecological groups. By elucidating the effects of different land use types on earthworm ecological groups and the impacts of their ecological group-specific casts on soil physicochemical properties, this study provides a theoretical basis for optimizing land management practices and the utilization of soil biological resources.

Key words: land use type, soil fertility, earthworm ecological group, organic matter, agricultural management practice