Fjölrit RALA - 15.06.2004, Side 116

Enchytreid reproduction test in volcanic material on Santorini.
E. Vavoulidou1, A. Oikonomou2 and F. Bartoli
1.NAGREF, Soil Science Institute of Athens, Greece, 2.NAGREF. Forest Research Institute ofAthens, Greece
3INRA, Laboratoire Sols et Environnement, Nancy, France
The aim of this study was to assess whether volcanic soils under Mediterranean climatic
conditions can be a habitat for soil organisms such as enchytreids (family of Oligochaeta).
Soil samples were taken from different sites on Santorini Island in Greece. Five cylindrical
cores (100 cm3 volume) per site were taken to collect samples for enchytreid abundance
studies. These soil samples were transferred to the laboratory where part of each sample was
used for counting the Enchytreid population using a stereoscope. The remaining soil from
each sample was placed in a box for incubation at 20°C for 10 weeks under a favourable soil
moisture regime (maximum water capacity 40-50%) for reproduction tests. The parent
material of all the soils studied is pumice and volcanic ash and the soils are fairly young, very
skeletic, with an extremely dry moisture regime.
The results were as follows:
Enchytraeids population density in the Santorini cultivated volcanic soils was consistently
low (1945 Ind/m2) and its increase after incubation was not statistically significant (2576
Ind/m2). The highest abundances prior to and after the incubation (2571 and 4286 Ind/m2
respectively) were found in the samples taken from sites with faba bean and pistachio nut
cultivations The mean lowest abundances prior to and after the incubation (0 and 330 Ind/m2
respectively) was found in samples taken from sites covered with natural vegetation.
From the micromorphological analysis of the three natural sites included in the study, no
significant enchytreid activity was observed. A few casts of dipteral larva were present in one
sample. This agrees with the complete lack of enchytreids in these three soils, which is in
contrast to the cultivated soils of the island, particularly the soils located on lower ground.
The preliminary results show that in extremely dry Mediterranean conditions, the young
volcanic soils do not enhance the soil fauna activities.
Further, more frequent, sampling needs to be performed in the “humid” period in order to
ascertain whether the relatively limited abundance of soil organisms (enchytreids) in April,
when this study was carried out, was due to the soil moisture regime at that time of year in
this volcanic habitat or is a more general phenomenon.
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