Biological and biochemical indicators in derelict soils subject to erosion

In 21 derelict soils from a semi-arid Spanish Mediterranean area, with a lithological substrate of loams, submitted to a high degree of erosion, several biological and biochemical properties indicative of the soil degradation level were determined. The organic matter content of these soils was very low (mean value = 11.8 g kg(-1)), approximately one-third of the average value for organic matter content of natural soils in the same zone. Biological properties such as basal respiration and biomass C also had low values and were positively correlated with the organic matter content. Low values for dehydrogenase and catalase activity were indicative of low biological activity of the degraded soils. A positive correlation was found between the hydrolases related with the N, P, C and S cycles (urease, proteases, beta-glucosidase and arylsulphatase), as well as between these hydrolases and the organic matter content. Principal component analysis showed that all the variables studied, except catalase and qCO(2), had a similar behaviour. There was a negative correlation between many of the properties studied and electrical conductivity, which agreed with the higher degree of biological and biochemical degradation found in gypsiferous soils with a higher salt content. Arylsulphatase and beta-glucosidase activity were the hydrolases most affected by soil erosion processes. (C) 1997 Elsevier Science Ltd.