Conclusions
The present study investigated the impacts of different land-use types
on denitrification-related microbial communities and associated
functional groups in freshwater rivers. Compared with natural land uses,
anthropogenic land uses (agriculture and urbanization) increased N
concentrations in river water, altering microbial community structure.
The anthropogenic land uses also shaped microbial functional groups and
stimulated microbially-mediated denitrification in the river basins. The
results of the present study could facilitate the estimation of land-use
type impacts on freshwater ecosystems through the analysis of microbial
functional groups. These conclusions will provide scientific references
for the impact of anthropogenic land on ecology of freshwater rivers and
land quality improvement in the Qinling Mountains. We recommend further
studies based on quantitative PCR, metagenomics, and metatranscriptomics
approaches to verify our findings. Furthermore, it is necessary to
determine the threshold N concentrations for denitrification efficiency
in ecosystems other than freshwater rivers, which can facilitate the
control of denitrification or N2O emissions caused by
anthropogenic disturbance.