Wetlands have numerous critical ecological
functions, some of which
are regulated by several nitrogen (N) and carbon (C) biogeochemical
processes, such as denitrification, organic matter decomposition,
and methane emission. Until now, the underlying pathways of the effects
of environmental and biological factors on wetland N and C cycling
rates are still not fully understood. Here, we investigated soil potential/net
nitrification, potential/unamended denitrification, methane production/oxidation
rates in 36 riverine, lacustrine, and palustrine wetland sites on
the Tibet Plateau. The results showed that all the measured N and
C cycling rates did not differ significantly among the wetland types.
Stepwise multiple regression analyses revealed that soil physicochemical
properties (e.g., moisture, C and N concentration) explained a large
amount of the variance in most of the N and C cycling rates. Microbial
abundance and diversity were also important in controlling potential
and unamended denitrification rates, respectively. Path analysis further
revealed that soil moisture and N and C availability could impact
wetland C and N processes both directly and indirectly. For instance,
the indirect effect of soil moisture on methane production rates was
mainly through the regulating the soil C content and methanogenic
community structure. Our findings highlight that many N and C cycling
processes in high-altitude and remote Tibetan wetlands are jointly
regulated by soil environments and functional microorganisms. Soil
properties affecting the N and C cycling rates in wetlands through
altering their microbial diversity and abundance represent an important
but previously underestimated indirect pathway.