Microbiological parameters as indicators of soil organic carbon dynamics in relation to different land use management

Abstract

Labile C fractions: microbial biomass C (MBC), K2SO4 extractable C ( $$ {\text{C}}_{{{\text{K}}_{ 2} {\text{SO}}_{ 4} }} $$ ) and the cumulated mineralized C in 21 days incubation at 28°C (C–CO2(21d)), were compared as land use indicators in a calcareous soil under three different management systems: native Querqus ilex forest (under and outside tree cover), a Pinus halepensis plantation, and cropped land (with cereals). Microbial biomass and activity were found to be low and coincided with high carbonate contents. As indicators of land use, $$ {\text{C}}_{{{\text{K}}_{ 2} {\text{SO}}_{ 4} }} $$ and C–CO2(21d) showed the same sensitivity as MBC. C–CO2 emissions were measured in an incubation experiment in order to study C mineralization kinetics. The data for cumulative amounts of C–CO2 released showed a good fit (R 2 > 0.94) to the first-order kinetic model C m = C o(1 − e−kt ). The kinetic parameters C o and C o k were affected by land use and especially by tree cover. Principal components analysis was applied to the data and the relationship among microbial metabolic quotient (qCO2), labile C pools, and MBC revealed a decrease in efficiency of organic substrate utilization with an increase in availability and lability of the organic matter.