Seasonal Evolution of Soil Dehydrogenase Activity at Two Different Depths in an Eucalyptus Stand and a Cultivated Field

Abstract

Dehydrogenase activity is a good indicator of changes in fertility, quality and microbiological status of the soil, which may vary seasonally. The aim of this study was to evaluate the seasonal evolution of this activity in two different soils (a cultivated field and an Eucalyptus stand) located in a periurban area of Coruna (NW Spain). From April 2004 to April 2005, a total of 38 soil samples were collected in the forest site and 152 samples in the cultivated field (two replicates at the top and the bottom of the hillslope at two depths: 0–5 cm and 5–10 cm). General soil properties were analyzed by routine methods, soil respiration under laboratory conditions and dehydrogenase activity using soluble tetrazolium salts. This activity ranged from 5 10−5 to 0.033 μg TPF g−1 soil 24 h−1 among individual samples in the forest, whereas it varied from 0.005 to 0.023 μg TPF g−1 soil 24 h−1 in the cultivated field. No differences with depth were observed in the cultivated field; whereas in the forest soil, higher activities were found in the top layer, which combined better conditions for microbial development. Dehydrogenase activity was affected by position and season in the cultivated field; higher values were detected in the top of the hillslope. In the forest site, higher values were observed in the top layer during spring and fall; due to favourable temperature and moisture conditions. In the cultivated field, dehydrogenase activity was correlated to soil basal respiration and soil pH, though, in the forest soil, no significant correlations were observed.