Influence of landscape pattern on benthic fauna in the main stream of the Heihe River

Studying the degree and mechanism of the impact of landscape pattern on the biodiversity of inland rivers is of great significance for the protection and restoration of inland river ecosystems in arid areas. Using landscape pattern and benthic fauna data, this study explored the relationship between landscape pattern and benthic fauna at different spatial scales using redundancy analysis and correlation analysis. The numbers and biodiversity of benthic fauna were higher in the middle reaches than in the upper reaches (in space) and higher in summer than in autumn (in time). The land use types in the riparian buffer zone were mainly grassland (32.58%), unused land (27.24%), and cultivated land (18.89%), and the landscape index analysis showed that the landscape types in the 600 m buffer zone were rich and spatially heterogeneous. Cultivated land is conducive to the survival of pollution-tolerant taxa and scrapers, whereas forest and grassland are conducive to the survival of cleaners and predators. Water areas are conducive to increasing the existing numbers and biodiversity of benthic fauna; in contrast, an increase in construction land and unused land poses a threat to benthic animals. The landscape indices patch density and Shannon’s diversity index were positively correlated with the number and biodiversity of benthic animals, whereas the contagion index was negatively correlated with the number and biodiversity of benthic animals. These findings indicate an increase in the landscape diversity and fragmentation along the main stream of the Heihe River and a decrease in the degree of landscape aggregation, which was conducive to the entry of particulate organic matter into the river with surface runoff and provided more food sources for benthic animals. The redundancy analysis showed that a 600 m buffer in the riparian zone is the optimal buffer zone scale for the impact of landscape pattern on river water quality and benthic fauna. Moreover, the rational allocation of landscape in the 600 m buffer zone should be considered, and the water ecological function of the arid inland area should be improved by increasing the planting density of forest and grassland species in the middle reaches, improving the aggregation and connectivity of forest and grassland landscapes, and controlling urban sewage discharge and centralized garbage treatment.