1. Riparian zones, an aquatic-terrestrial interface, can intercept more than half of nitrogen (N) exported from terrestrial ecosystems to adjacent rivers, primarily by denitrification processes. However, damming has disrupted natural patterns and processes of flooding and vegetation community assemblages, and yet little is known about how hydrological changes and ecosystem restoration affect the biogeochemical functioning in the riparian ecosystems.2. We conducted an in situ experiment to evaluate the effects of hydrological change (e.g. altering flooding intensity and frequency) and restoration approaches (e.g. natural regeneration and active revegetation) on denitrification rates and the abundance of denitrifier genes in the riparian zone of the Three Gorges Reservoir, China.3. Our results showed that active revegetation did not significantly increase denitrification rates compared to the natural regeneration, but their underlying mechanism was different. At the natural regeneration area, the denitrification rate was primarily regulated by soil properties and abundance of nosZ gene, while at the active revegetation area, it was controlled merely by the abundance of nosZ gene. In addition, vegetation types showed little effect on the soil denitrification process, and the denitrification rate decreased with flooding intensity by reducing denitrifier gene abundance.4. The periodic flooding treatment doubled the denitrification rate compared with the no flooding treatment, which might be attributed to the enhancement of soil carbon availability. Our results suggest that in terms of N removal via denitrification processes, natural regeneration is a priority approach to restoring degraded riparian ecosystems.
Soil microorganisms play a crucial role in ecosystem processes and functions, but how their co‐occurrence networks respond to restoration of degraded ecosystems remains poorly understood.
Here, we examined the effects of revegetation on the structure and function of the soil microbiome, including soil microbial network complexity and stability, in a novel riparian ecosystem with winter submergence opposite to the natural hydrological regime.
We found that extreme flooding intensity (30 m submergence up to 286 days per year) reduced microbial α‐diversity and network stability (robustness) but increased network complexity including network connectivity, connectance and average clustering coefficient over a 3‐year period, and those effects were mitigated by active revegetation in comparison with natural regeneration. Revegetation increased microbial network stability directly by decreasing network complexity, while extreme flooding regulated network stability indirectly by changing the soil total carbon content. Nevertheless, those dynamics of microbial network were coupling with soil microbial functions such as greenhouse gas (e.g. CH4, CO2 and N2O) fluxes and nutrient cycling.
Synthesis and applications: This study provides evidence to support the critical role of revegetation in preserving soil microbial network stability and functions under changing hydrological regime.
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