摘要：The behaviour of earthworms, their role in
organic matter incorporation into the soil, and the
influence of aridity in such processes in arid and
semiarid regions have scarcely been studied. In
this study, physico-chemical analyses of the casts
and the surrounding no-till agricultural soils
of three experimental sites representing an aridity
gradient in Navarre (NW Spain) were done. The casts
were formed by the activity of the only anecic
species, Scherotheca gigas
(Dugès, 1828), ubiquitous in no-till soils
in this region. We observed a significant depletion
of clay and higher concentration of total organic C
and labile C in the form of particulate organic
matter (POM) in the casts as compared to the
surrounding soil, suggesting selective ingestion of
soil by S. gigas. This, together
with the observation of increased concentration in
POM with increasing aridity, suggests a major role
of this species in the observed progressive gains
of organic C stocks in no-till soils in the
region.
