and qCO2 can provide indirect evidence that soil fungi are more
efficient than bacteria in substrate utilization and efficiency (Six
et al., 2006). Fungal-dominated soils have slow C turnover rates
and greater growth efficiency compared with bacterial-dominated
soils because (1) fungi incorporate more C into biomass than
bacteria, (2) they have more recalcitrant cell walls than bacteria,
and (3) they facilitate C stabilization and protection by enhancing
soil aggregation (Six et al., 2006). The qCO2 values confirm well our
findings for MBC/MBN and furthermore support the apparent
sensitivity of the microbial community to tillage practices. In
addition to MBC/MBN ratio, the observed decline in the qCO2 under
RT might thus provide additional evidence of higher fungal
biomass in RT than CT soils. Apparently, the environmental
conditions for soil microflora would be more favorable in RT than
CT soils and during the later years of tillage operation, as reflected
by the declining qCO2 values after tillage treatments, suggesting a
more sustainable microbial community. In contrast, increases in
the qCO2 values under CT could indicate both disturbance and
microbial stress as a result of the progressive loss of soil aggregates
(Kabiri et al., 2015) and slow SOM losses, in particular the most
labile soil C fraction such as microbial biomass. CT causes serious
disturbance to the soil environment and an increased qCO2 has
been interpreted as a response by soil microflora to adverse
environmental conditions and disturbance (Wardle and Ghani,
1995; Anderson and Domsch, 2010). In addition, the recent
incorporation of an available substrate into the CT plots (i.e.,
ploughed-in barley and clover roots and residual top material) may
have preferentially stimulated the soil bacterial population with
large qCO2 values. Large qCO2 levels in CT soils could also be
ascribed to greater levels of readily degradable C content released
after the destruction of soil macroaggregates during intensive
tillage practices (Kabiri et al., 2015) and short turnover times of the
microbial biomass