1 Earthworm assemblages in different intensity of agricultural uses and their 2 relation to edaphic variables

18 The objective of this study was to relate the earthworm assemblage structure with three 19 different soil use intensities, and to indentify the physical, chemical, and 20 microbiological soil variables that are associated to the observed differences in the 21 earthworm assemblage structure between soils. Three soil uses were evaluated: 1Fifty 22 year old naturalized grasslands, low use intensity; 2Recent agricultural fields, 23 intermediate use intensity, and 3Fifty year old intensive agricultural fields, high use 24 intensity. Three different sites for each soil use were evaluated from winter 2008 25 through summer 2011. Nine earthworm species were identified across all sampling 26 sites. The sites shared five species: the native Microscolex dubius, and the introduced 27 Aporrectodea caliginosa, A. rosea, Octalasion cyaneum, and O. lacteum, but they 28 differed in their relative abundances according to the system. The results show that the 29 earthworm community structure is linked to and modulated by soil properties. Both, 30 species abundance and diversity showed significant differences depending on soil use 31 intensity. A PCA principal component analysis showed that species composition is 32 closely related to the environmental variability. The ratio of native to exotic species was 33 significantly lower in the intensive agricultural system when compared to the other two, 34 lower disturbance Systemssystems. Microscolex dubius was shown to be related to the 35 naturalized grasslands and it was associated to soil Ca, pH, Mechanical Resistance, and 36 to microbial respiration. Aporrectodea caliginosa was related to high K levels, low 37 enzymatic activity, slightly low pH, and low Ca, and appeared related to the highly 38 disturbed environment. Eukerria stagnalis and Aporrectodea rosea, commonly found in 39 the recent agricultural system, were related to high soil moisture condition, low pH, low 40 Ca and low enzymatic activity. These results show that earthworm assemblages can be 41 good descriptors indicators of different soil use intensities. In particular, Microscolex 42 dubius, Aporrectodea caliginosa, and Aporrectodea rosea, showed different temporal 43 patterns and species associations, due to the changes in soil properties attributable to 44 soil use intensity, defined as the amount and type of agricultural operations. 45 46