C. Fragoso et al., AGRICULTURAL INTENSIFICATION, SOIL BIODIVERSITY AND AGROECOSYSTEM FUNCTION IN THE TROPICS - THE ROLE OF EARTHWORMS, Agriculture, ecosystems & environment. Applied soil ecology, 6(1), 1997, pp. 17-35
Earthworm biodiversity is modified when forests and natural savannas a
re replaced by agroecosystems; these changes can be studied from the t
axonomic and functional point of view. In the first case the number an
d origin (native or exotic) of species is important, as well as the ge
ographic scale of the study (local or regional), The functional approa
ch considers the ecological groups (epigeic, endogeic, anecic), which
have different effects on soil function, Studies in Mexico, Peru and I
ndia reveal that agroecosystem earthworm communities (as compared with
those in the undisturbed ecosystem) have lower species richness, lowe
r number of native species, lower number of ecological groups and a pr
edominance of endogeics, Therefore the role of endogeic species in int
ensifying agroecosystems is likely to be more important for soil funct
ion, especially because they act as ecosystem engineers and through th
eir mutualistic interactions with microflora, selective ingestion of s
oil particles, high rates of ingestion and production of casts, galler
ies, burrows and chambers can affect nutrient and organic matter dynam
ics and other pedological processes. Epigeic and anecic species do not
appear to be as widespread in agricultural systems and their dependen
ce on a litter layer for survival implies that litter management pract
ices must be implemented for their role in soil function to be of impo
rtance. The role of earthworms in enhancing primary production depends
on the synlocalization (in the same place) and the synchronization (a
t the same time) of their activities with the period and the sphere of
active root growth and nutrient demands. Several field studies have f
ound significant yield increases with earthworm inoculation, though mo
re research is needed. Incorporation of information on earthworm life
histories, field population variations, ecological strategies and shor
t and long term effects on soil properties, in addition to plant and e
nvironmental factors (climate, soil, cropping period and management of
the agroecosystem), are essential to properly assess the potential ro
le of a particular earthworm species on plant production.