Optimizing vegetation pattern for the riparian buffer zone along the lower Yellow River based on slope hydrological connectivity

Abstract

Riparian buffer zone is important ecological transitional region between river and upland. Restoring the degraded vegetation system is important for preventing soil erosion, improving ecological environment and helping to achieve the sustainable development of ecosystems. Based on the scenario simulation of vegetation pattern and flow length index, we analyzed the responses of hydrological connectivity to vegetation pattern under different vegetation coverages and slope gradients, and explored the optimal vegetation pattern of soil and water conservation in riparian buffer zone in the lower reaches of the Yellow River. The results showed that the midslope-coarsness-clustered distribution of vegetation configuration, which exhibited the shortest flow length and the weakest hydrological connectivity, being the optimal vegetation pattern for controlling slope runoff generation and flow concentration. For the optimal vegetation pattern, its flow length increased with increasing slope length, namely, the longer slope length the more significant difference of hydrological connectivity between different slope gradients. Meanwhile, flow length of the optimal vegetation pattern decreased with increasing vegetation coverage. The differences between different slope gradients were obvious under low vegetation coverage, while it was unobvious on slope with vegetation coverage of 45%. Compared with the irregular variation trend of flow length on the actual vegetation slope, there was a consistent trend of first increase and then decrease on the simulated slope with the optimal vegetation pattern. Within the pre-set slope gradient range (5°-20°), the optimal vegetation pattern changed the variation of flow length between different slope gradients in the process of coverage change, which highlighted the influence of riparian buffer zone vegetation pattern on hydrological connectivity.