Revegetation potential assessment on the Hanfeng Lake of the Three Gorges Reservoir: evidence from soil seed bank

Abstract

The hydrological regiments of large reservoirs worldwide always are always artificially controlled, significantly impacting the ecosystems of the water level fluctuation zone (WLFZ). In China, the anti-natural periodic water level fluctuation has led to plant diversity decline in the WLFZ of the Three Gorges Reservoir (TGR), causing seriously ecosystem problems. Attempts on revegetation was carried out since 2009, which mainly aimed to re-establish the natural riparian vegetation including trees, shrubs, and herbs. Whereas, the revegetation efficient has not yet been evaluated. To evaluate the effectiveness of the revegetation, the soil seed bank (SSB), aboveground vegetation (AGV), soil physiochemical parameters and inundation disturbance were integrated to assess the potential of revegetation in the WLFZ of the Hanfeng Lake. The results showed that seed reproduction is the main reproductive mode of aboveground communities in both artificial and natural restoration sites. The similarity between SSB and AGV increased as compared to that of the pre-revegetation project implement. The diversity of SSB was higher than that AGV, furthermore, diversity increased on artificial revegetation site was found. The seed density on natural revegetation sites (6396.97 ± 4699.49 seeds/m2) was significantly higher than that of the airtificial restoration site (p < 0.01). Soil nutrients were richer in the restoration sites compared to the reference sites. However, the correlation between soil physiochemical parameters and SSB/AGV varied, indicating that potential succession in vegetation may still occur. Revegetation potential assessment revealed that a slightly higher revegetation ability in artificial revegetation sites comparing to that of the natural sites, while the revegetation potential was not significant between them, showing the challenges on revegetation of the WLFZs in the TGR region. To better maintain the ecological functions and sustainability of the fragile ecosystem in the WLFZs, intergrating natural based solutions with approcimiate artificial measurements are recommanded.