Worldwide hydroengineering, such as reservoir construction, creates the riparian zones with novel hydrological regime, which causes biodiversity loss and ecosystem degradation. Active revegetation (AR) and natural regeneration (NR) have been widely used in degraded riparian ecosystems to recover biodiversity and ecosystem functions. However, how restoration approaches and hydrological changes influence the key processes of carbon and nitrogen cycling in reservoir riparian zones has not been elucidated.

The Systems Ecology Group of Wuhan Botanical Garden investigated the effects of restoration approaches and hydrological changes on soil properties, vegetation diversity, microbial characteristics, denitrification rates, and greenhouse gas fluxes at three flooding zones (extreme flooding zone, severe flooding zone, and moderate flooding zone) in both AR and NR sites in the Three Gorges Reservoir.

Results revealed that compared with NR, AR did not significantly impact vegetation diversity, the diversity of microbial communities, and soil denitrification rates, but reduced soil ammonium and total carbon contents. Compared with other two flooding zones, the extreme flooding zone was observed to have higher denitrification rates and CO₂ fluxes, which could be attributed to the high nutrient content. Furthermore, the effects of flooding zone were found to override the impacts of restoration approaches.

This study enlightens the restoration strategies for degraded riparian ecosystems. The interactions among soil, plants, microbes, and biochemical processes may be beneficial for modeling and predicting future impacts on N removal efficiency and regulating climate in restored riparian ecosystems.

The research titled “Effects of flooding outweigh those of vegetation restoration on key processes of carbon and nitrogen cycling in a degraded riparian zone” was published in the Catena. It was supported by the National Natural Science Foundation of China and Youth Innovation Promotion Association of the Chinese Academy of Sciences.

 (a) Effects of flooding zones and restoration approaches on microbial α diversity (Chao1). (b) NMDS ordination of soil microbial community profiles. The empty triangles represent active revegetation, whereas the solid triangles represent natural regeneration. The green, blue, and orange colors represent MFZ, SFZ, and EFZ, respectively. (c) Microbial co-occurrence networks were affected by the restoration approaches and zones. (d) Node connectedness (normalized degree) and centrality (betweenness) of microbial co-occurrence networks were affected by the restoration approaches and flooding zones. (Image by CHEN Meiping)