Ultrashort-term responses of riparian vegetation restoration to adjacent cycles of ecological water conveyance scheduling in a hyperarid endorheic river basin

Abstract

The management of ecological water conveyance (EWC) can allow riparian vegetation communities to survive the threat of degradation in hyperarid inland areas and promote the health of groundwater-recharged riparian ecosystems. However, the ultrashort-term effects of periodic EWC scheduling on riparian vegetation remain unclear. This study explored the spatiotemporal differentiation in species structure (herbs, shrubs, and trees), diversity (measured by the Simpson, Shannon-Wiener, Pielou, and Margalef indices), stability (evaluated via Godron fitting distances and abundance-biomass comparison curves), and integrity (proxied by the vegetation-based index of biotic integrity) of vegetation communities in the downstream Heihe River Basin, China. Empirical orthogonal function, Pearson correlation, canonical correspondence analysis (CCA), and partial CCA methods were used to evaluate the effects of dominant habitat environmental factors from the hydrogeographic features, soil physicochemical properties, and anthropogenic impacts. The results showed that the riparian vegetation community diversity, stability, and integrity varied moderately to slightly with hierarchical distance from near wetlands (<200 m; containing mainly herbs) to far desert edges (>800 m; occupied by shrubs/subshrubs). The middle transition zone (200-800 m; occupied mostly by trees/subtrees) had the best diversity and integrity but relatively poor stability. The most significant influencing factors were EWC and soil moisture. The simple diversity, fair-level integrity, and disturbed but not irreversibly damaged stability of the vegetation community were generally improved by 14.82%, 20.33%, and 30.57%, respectively, in the pre-EWC period but worsened in the post-EWC period. The difference in spatially distributed EWC quantities caused more apparent vegetation restoration in high water-supplied subareas where certain biological community instability existed. Therefore, adequate EWC management can be considered a prerequisite for the maintenance of high richness and structural stability in local communities and requires a good balance between interregional vegetation abundance and enhanced environmental tolerance.

Keywords: Community analysis; Ecological water conveyance; Habitat environmental factors; Heihe river; Riparian vegetation.