Fjölrit RALA - 15.06.2004, Side 115

In addition, soils were analysed for particle size distribution, organic carbon (Walkley Black
method), CaCOs, total N, cation exchange capacity, exchangeable cations, Olsen P, pH (in a
water-saturated soil paste), and mineral N (ammonium and nitrate).
All soils were sandy loam to loamy sand in texture (SL-LS) and had an acid to slightly
alkaline reaction. Free CaC03 was very low except in one region with values up to 15%.
This is probably explained by the presence of underlying non-volcanic rock formations. The
organic matter content was very variable, ranging between 0.5 to 9.6%. All the agricultural
soils contained >5 mg kg'1 of available P and two thirds contained > 20 mg kg"1. However, 3
of the 6 natural sites contained only trace amounts. Available K was in the range 0.2 to 0.6
cmol kg"1 soil for most soils. In general, the cation exchange capacity (CEC) was very low,
less than 10 cmol kg'1. Total nitrogen (N) was relatively low, but the ratio of total organic
carbon to total nitrogen (C: N) was in the normal range (2-14) for inorganic soils. In addition,
the concentrations of the nitrate and ammonium ions were found to be at normal levels.
No earthworms (Lumbricidae) were found at any of the sites on the island. Enchytreids
were found at only 2 of the natural sites with very low abundance (800 and 1600 Ind m"2). A
higher percentage (56%) of agricultural soils contained enchytreids, but again their abundance
was generally low, with a mean population of 2700 Ind m"2.
Hydrolytic enzyme activity was low in most soils sampled when compared to data for soils
from wetter regimes (Marx et al, 2001). Enzyme activity is in general strongly related to soil
biological activity, and in soils with low levels of organic matter the activity of hydrolytic
enzymes such as cellulase is low. The few soil samples from Santorini that had higher levels
of organic matter showed higher levels of enzyme activity.
In conclusion, on the basis of the above data, the soils of Santorini do not show significant
biological activity during the seasons in which the samples were taken. This is likely to be a
reflection of the relatively young age of the soils, and the low levels of organic matter.
However the situation is likely to be complicated by local factors such as micrometeorological
conditions and the impact of parent material on soil water holding properties. It is important
that investigations be extended to the wet period of the year in order to confirm these initial
findings.
References
Dick, R. P. 1994. Soil enzyme activity as indicators of soil quality. In "Defining Soil Quality
for a Sustainable Environment" (J. W. Doran, D. C. Coleman, D. F. Bezdicek and B. A.
Stewart, eds.), pp. 107-124. Soil Science Society of America, Madison, Wisconsin.
Marx, M.-C., Wood, M., and Jarvis, S. 2001. A microplate fluorimetric assay for the study of
enzyme diversity in soils. Soil Biology & Biochemistry 33, 1633-1640.
Misopolinos, N., Syllaios, N., Prodromou, K. 1994. Physiographic and soil mapping of
Santorini island. Edited by the Laboratories of Soil Science and Remote Sensing of the
School of Agronomy, Aristotle University of Thessaloniki. ppl 10 (in Greek).
92