Enzyme activities in undisturbed and disturbed forest soils under oak (Quercus brantii var. persica) as affected by soil depth and seasonal variation

Abstract

The seasonal dynamics of acid phosphatase, alkaline phosphatase and dehydrogenase and the relationship of their activities to soil depth were studied in the undisturbed forest soils under oak and compared with the disturbed one. At each site, four soil samples were randomly taken at depth of 0-20 cm in May, July, September and November and at three different depths (0-10, 10-20 and 20-30 cm) in November. Enzymes were assessed by reaction with substrate and photometrical method. The activity of acid and alkaline phosphatase and dehydrogenase was greater at undisturbed site than disturbed sites. These results signalized a high activity of roots for the secretion of acid phosphatases. High alkaline phosphatase activity reflected a good status of soil microorganisms. Moreover alkaline phosphatase activity was 2.1 to 2.93 times greater than acid phosphatase activity at both sites. Alkaline and acid phosphatase and dehydrogenase activity showed a seasonal pattern with maxima in summer and minimum in autumn. Assay of acid phosphatase activity showed significant (p<0.01) increasing of its activity with soil depth increment at undisturbed site whereas this increasing trend was not observed at disturbed site. The depth pattern of alkaline phosphatase activity was totally different. At undisturbed site, alkaline phosphatase activity significantly (p<0.01) decreased with soil depth and visa versa in the disturbed site. At both sites, dehydrogenase activity significantly (p<0.01) decreased with soil depth increment. In conclusion the higher activity of phosphatase and dehydrogenase at undisturbed sites shows the effect of land use management and for understanding soil ecosystem functioning. © 2008 Asian Network for Scientific Information.