Microbial functional groups under different land-use types
To study the influence of environmental factors and land-use types on
microbial functioning in different river areas, microbial functional
groups were predicted based on 16S rRNA gene sequences using FAPROTAX
database. Subsequently, Pearson’s
correlations between microbial functional groups and environmental
factors or land-use types were analyzed.
Numerous functional groups were
associated with nitrate denitrification, nitrite denitrification,
denitrification, N respiration, N fixation, and iron (Fe) and manganese
(Mn) respiration in the water of river areas dominated by agricultural
land (Weihe River). The predicted functions were significantly
positively correlated with
multiple environmental factors
(e.g., NH4+-N, TP, TN,
NO3--N,
and
NO2--N) and land-use types
(agricultural and urbanized land), whereas they had negative
correlations with DO, pH, forest land, and shurb land.
There were few denitrification-related functional groups in the water of
river areas dominated by forest land (Hanjiang River and Qinling
tributaries). However, numerous functional groups were associated with
aerobic anoxygenic phototrophy, oxidation,
nitrite ammonification, nitrate
ammonification, nitrification, aerobic nitrite oxidation, anoxygenic
photoautotrophy, and aerobic ammonia (NH3) oxidation in
the water of Hanjiang River. The functional groups associated with N
fixation were significantly positively correlated with
NO2--N, shrub land, and forest land,
but negatively correlated with DO,
NH4+-N, pH, T, agricultural land,
grassland, and urbanized land. Furthermore, there were few functional
groups associated with N and P cycles in the water of Qinling
tributaries. The relative abundances of N metabolism-related functional
groups were significantly higher in the water of Weihe River than in
other areas, whereas the relative abundances of carbon
metabolism-related functional groups were distinctively higher in the
water of Hanjiang River than in the other areas (Fig. 5).