Diversity and Distribution of Riparian Arthropods in the Drawdown Zone of China's Three Gorges Reservoir

Abstract

Riparian zones are interesting habitats as they are important transitional zones between terrestrial and aquatic ecosystems, but highly threatened by human disturbances. They support a high arthropod diversity as they experience periodic flooding disturbance and sharp environmental gradients. Their associated arthropod fauna are of high conservation value. Nevertheless, their arthropod diversity remains largely unknown, and its distribution pattern along elevational gradients is poorly understood. Few data are available on the effects of flood regimes and other factors in determining riparian arthropod communities. In this study, we investigated the diversity and distribution of riparian arthropods along an elevational gradient and determined the major factors structuring the arthropod communities in the drawdown zone of the Three Gorges Reservoir, China. Significant compositional and structural changes of riparian arthropod communities were observed along the test elevational gradient. The abundance and richness of riparian arthropods increased with elevation. The relative abundance of predators decreased with elevation, whereas the saprovores and omnivores showed an upward trend along the elevational gradient. Redundancy analysis showed that there were significant interactions between the flood regimes, plant communities, and soil conditions. Among these environmental factors studied, flood duration was the main factor in structuring the riparian arthropod communities. Conservation and restoration strategies should consider flood duration in the operation of large reservoirs because riparian arthropods are particularly sensitive to flood regimes.

Keywords: drawdown zone; flooding; riparian arthropod; spatial distribution; the Three Gorges Reservoir.