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

19 The objective of this study was to relate earthworm assemblage structure with three 20 different soil use intensities, and to indentify the physical, chemical, and 21 microbiological variables that are associated to the observed differences in earthworm 22 assemblage structure between soils. Three soil uses were evaluated: 1Fifty year old 23 naturalized grasslands, low use intensity; 2Cattle-grazingRecent agricultural fields, 24 intermediate use intensity converted to feedlot within the two years before the start of 25 this work, and 3Fifty year old intensive agricultural fields, high use intensity. Three 26 different sites for each soil use were evaluated from winter 2008 through summer 2011. 27 Nine earthworm species were identified across all sampling sites. The sites shared five 28 species: the native Microscolex dubius, and the introduced Aporrectodea caliginosa, A. 29 rosea, Octalasion cyaneum, and O. lacteum, but they differed in their relative 30 abundances according to the system. The results show that earthworm community 31 structure is linked to and modulated by soil properties. Both, species abundance and 32 diversity showed significant differences depending on soil use intensity. A PCA 33 analysis showed that species composition is closely related to the environmental 34 variability. The ratio of native to exotic species was significantly lower in the intensive 35 agricultural system when compared to the other two, lower disturbance Systems. 36 Microscolex dubius was shown to be related to the naturalized grasslands and it was 37 associated to Ca, pH, Mechanical Resistance, and to respiration. Aporrectodea 38 caliginosa was related to high K levels, low enzymatic activity, slightly low pH, and 39 low Ca, and appeared related to the highly disturbed environment. Eukerria stagnalis 40 and Aporrectodea rosea, commonly found un thein cattle-grazingrecent agricultural 41 system, were related to high soil humiditymoisture condition, low pH, low Ca and low 42 enzymatic activity. These results show that earthworm assamblages can be good 43 descriptors of different soil use intensities. In particular, Microscolex dubius, 44 Aporrectodea caliginosa, and Aporrectodea rosea, showed different temporal patterns 45 and species associations, due to the changes in soil properties attributable to s oil use 46 intensity, defined as the amount and type of agricultural operations. 47 48 Comment [CEC1]: Related to the Cattle-grazing comment by reviewer 1 Comment [CEC2]: As requested by reviewer 1