Enzyme activities as affected by mineral properties in buried volcanic soils of southern Italy

Abstract

The aim of the study was to explore the likely relationships between physico-chemical and biochemical properties in buried volcanic soils of Italy, showing different degree of andic properties extent. Indeed, buried soils have the advantage to be less directly affected by anthropic impact, fresh carbon (C) inputs and environmental conditions (such as temperature, humidity, pH etc.). Two soil chronosequences, developed in different volcanic geomorphological environments, were analysed in Campania region (Italy) to assess the variations of biochemical properties according to soil andic properties. Chemical properties enabled to classify these soils as Andosols of silandic type (e.g. dominated by imogolite-type materials – ITM). As regards the relationship between soil mineral properties and biochemical activity, a positive correlation was found between enzymes and Alpy but not with Feox, Siox or ITM content. However, acid phosphomonoesterase, chitinase, leucine aminopeptidase, arylsulphatase, butyrate esterase activities and enzymes involved in C cycle (SEIc) were significantly different among soils, showing higher activity rates in soils with more pronounced andic properties. Conversely, when enzyme activity was expressed per unit of organic C (specific enzyme activity) it was significantly higher in weakly andic soils. The specific enzyme activity was particularly sensitive to the increase of Alox + 1/2Feox only for values <1%, typical of low developed andic properties, pointing to an important role of Al in controlling the interactions between the ITM mineral phase and soil enzymes. In conclusion, the soil mineralogical properties influenced the potential hydrolysis of organic C whose stabilization in the soil matrix may be affected by ITM presence and the stable interaction with soil enzymes. However, in order to establish if soils’ biochemical activity may be affected by andic properties, additional research should be addressed to cover all types of Andosols, including the aluandic ones.