reported that differences in
plant species composition and soil properties could be responsible
for the variation in dehydrogenase, and also that this enzyme
activity was positively and significantly correlated with soil pH but
no correlation with total soil C and N. However, Leiros et al. (2000)
reported a clear positive relationship with soil C, probably in the
forest ecosystems they studied soil microorganisms are nutrient
rather than C limited. Since dehydrogenase did not respond to the
variation of C contents or the C:N ratio, rather site factors (forest
canopy, species composition, soil texture, soil pH and available
nutrients) and seasonal sampling data were the greater determinants
of the variation in dehydrogenase than management factors
(Quilchano and Maranón, 2002 ˜ ). Nevertheless, it is also very diffi-
cult to compare the values obtained with different experimental
protocols (especially in the case of enzymatic activities), either
because there are no standardized methods or due to the soil
samples been subjected to different pre-treatments prior to their
analysis, such as pH, sample collection, and sample storage, prior
to their analysis