Hydrochemical Characteristics of Rainfall Redistribution in Three Forest Ecosystems in a Rocky Hillslope of North China

ABSTRACT The Yanshan mountainous region in North China, characterised by its rocky and shallow soils, is an ecologically fragile area prone to significant water and nutrient loss. Forest vegetation plays a crucial role in maintaining the stability of the local ecosystem. However, the redistribution characteristics of rainfall and its associated nutrients—key direct sources of water and nutrients for forest ecosystems—have not been systematically studied in this region. In this study, three typical vegetation types on the same hillslope were selected to minimise variations in microclimate and site conditions. Field measurements of hydrological fluxes and laboratory analyses of carbon, nitrogen and phosphorus concentrations were conducted from April to September 2024 to investigate the effects of forest stands and rainfall event characteristics on water and nutrient redistribution at the canopy interface. The results indicated that Quercus variabilis , a deciduous species with a more open branching structure and a relatively low mean leaf area index (LAI), allowed greater water flux to reach the forest floor. In contrast, the denser canopies of Platycladus orientalis and Pinus tabuliformis resulted in higher interception losses. During the observation period, the amount of canopy interception by Quercus variabilis was 32% and 34% lower than that of Platycladus orientalis and Pinus tabuliformis , respectively. In terms of nutrient redistribution, solute concentrations varied significantly with rainfall intensity. The highest solute concentrations were observed during light rain events, and concentrations under Platycladus orientalis and Pinus tabuliformis were generally higher than those under Quercus variabilis , which was closely related to the accumulation time of deposits on the canopy and their dissolution into rainfall. Ultimately, the source–sink dynamics of nutrients at the canopy interface were jointly regulated by water flux and solute concentration. This study found that the canopy acted as a continuous net source of carbon. For nitrogen and phosphorus, however, it generally functioned as a net source but shifted to a net sink during light rain events. Among the stands, Pinus tabuliformis exhibited a significant advantage in the transfer of carbon and nitrogen, with net fluxes reaching the forest floor being 29% and 12% higher, respectively, than those under Quercus variabilis . This study elucidates the patterns of rainfall‐related water and nutrient redistribution by typical vegetation in a rocky mountain area of North China, providing valuable insights for optimising forest composition to enhance the stability of water and nutrient dynamics in the ecosystem.