Measurements of ecosystem broad function and specialized
function
The basal microbial respiration
(mSR) was selected as a broad
function in this study, because it widely existed in almost all
micro-organisms and had been considered as a proxy of total biological
activity without environmental limitation (Campbell et al. 2003;
Delgado-Baquerizo et al. 2016a). The mSR was measured by
quantifying the carbon dioxide (CO2) from the equivalent
dry-weight fresh soil in ideal incubation environment. The details were
described in previous studies (Qiao et al. 2014; Zhang et
al. 2016).
The specialized functions (i.e. net nitrification rate, NR and potential
nitrification rate, PNR) were measured, because they were a key
microbial driven process in the N cycle and characterized by the
oxidation of ammonia to nitrate via nitrite. Microbes holding the gene
encoding ammonia monooxygenase (AMO) are the first and rate-limiting
step of nitrification process (Hatzenpichler 2012; Trivedi et al.2019b; Jia et al. 2020). The NR and PNR were measured with the
soil samples incubating in field and a standard environment (25 ℃ and
60% of the water saturation holding content) during a 14-day periods,
respectively. The NR was calculated as the difference of
NO3--N concentrations at the beginning
and the end of the incubation periods.