02644naa a2200193 a 450000100080000000500110000800800410001910000140006024500840007426000090015852018590016770000160202670000160204270000170205870000190207570000190209470000160211377303210212913148702008-09-18       2008    bl uuuu     u00u1 u    #d1 aPIRON, D.  aSoil tillage practices and the spatial organisation of earthworm biostructures.  c2008  aEarthworm biostructures are widely accepted for their distinctiveness in term of soil structure, organic matter availability or biological activities. However, while the determinism of earthworm activities has been investigated since a long time, only few studies have reported data on the spatial distribution of earthworm biostructures according to agricultural practices. Therefore, many soil profiles corresponding to conventional tillage (CT) and no-tillage treatment (NT) were thinly sketched according to the typology of soil morphologic features (physicogenic and biogenic facies). Then, GIS tool were used (i) to quantify the areas of biostructures according to the depth, (ii) to qualify the size and the shape of the facies (iii) and to detect their preferential orientation. This study showed that the area of biogenic facies clearly differed between 0 and 25cm, with the significant highest value for NT treatment (25 to 35%) vs 10% for CT treatment. On the other hand, the percent of biogenic facies that decreased gradually below 25cm did not differ significantly between the agricultural treatments. Facies of bioturbation was composed by a major part of cast aggregates assembling (B3), dominated by welded casts (B3i), while the facies B1 (burrows) never exceeded 1% of the soil profile. The size of B3 facies could reach 80cm², but most of them (80%) were ranged between 4 and 20cm². In addition, the shape of the facies B3 appeared frequently circular, even if a contortioned shape characterized often the welded casts assembling (B3i). In No-Tillage treatment, the impact on earthworm activities of past ploughing was noticed by the oblique orientation for many facies B3i between 10 and 25cm. Our study showed that earthworm activities under the constraint of soil agricultural practices are an important process of soil structure1 aPÉRÈS, G.1 aBELLIDO, A.1 aHALLAIRE, V.1 aBOTTINELLI, N.1 aMENASSEREI, S.1 aCLUZEAU, D.  tIn: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.