Rainfall interception by leaf litters: What happens with fallen leaves of different types and mixing degrees under simulated rainfall?

Abstract

As a crucial component within the vertical structure of the forests, leaf litter plays a significant role in the hydrological effects of the forest ecosystem. Studying the impact of different types of leaf litter combinations on the hydrological performance, as well as understanding how the ratio of leaf types in the litter layer influences it, are crucial for achieving a deeper comprehension of the role of the litter layer in forest hydrological processes. The objectives of this study were to determine the rainfall interception characteristics of single leaf litters with different types (Pinus massoniana, Cinnamomum camphora and Magnolia grandiflora) and mixing degrees (P. massoniana × C. camphora, P. massoniana × M. grandiflora, and C. camphora × M. grandiflora, with mixing ratios of 1:3, 1:1, and 3:1) under various slope gradients (0°, 5° and 25°). The results showed that with varying combinations of leaf litters and different mixing degrees, there existed certain disparities in runoff mitigation efficiency. In particular, the response time of the P. massoniana × M. grandiflora to rainfall gradually advanced as the proportion of P. massoniana increased. The maximum and minimum interception capacity of the leaf litters were both highest for C. camphora, and minimum interception capacity of the mixed litters of P. massoniana × C. camphora decreased with an increasing proportion of P. massoniana. When C. camphora accounted for a larger proportion in the mixed litters of C. camphora × M. grandiflora, the minimum interception capacity was larger. In the combination of P. massonian × C. camphora, the proportion of infiltration flow was the highest when the mixing ratio was 1:1, while that of slope and lateral flow was the lowest. On the sloped land, the infiltration flow of P. massoniana × M. grandiflora increased with the increasing proportion of P. massoniana, while the slope flow was opposite. Mixtures of litters affect the accumulation spatial structure of the litter layer, consequently altering the interception and redistribution characteristics of rainfall. The research provides a reliable foundation for objectively assessing the water transfer mechanism and conservation function of the litter layer.