Exploring the stemflow dynamics and driving factors at both inter- and intra-event scales in a typical subtropical deciduous forest

Numerous efforts have been made to understand stemflow dynamics under different types of vegetation at the inter-event scale, but few studies have explored the stemflow characteristics and corresponding influencing factors at the intra-event scale. An in-depth investigation of the inter- and intra-event dynamics of stemflow is important for understanding the ecohydrological processes in forest ecosystems. In this study, stemflow volume (F-V), stemflow funnelling ratio (F-R), and stemflow ratio (F-%) from Quercus acutissima and Broussonetia papyrifera trees were measured at both inter- and intra-event scales in a subtropical deciduous forest, and the driving factors, including tree species and meteorological factors were further explored. Specifically, the F-V, F-R and F-% of Q. acutissima (52.3 L, 47.2, 9.6%) were lower than those of B. papyrifera (85.1 L, 91.2, 12.4%). The effect of tree species on F-V and F-% was more obvious under low intensity rainfall types. At the inter-event scale, F-V had a strong positive linear correlation with rainfall amount (G(P)) and event duration (D-E) for both tree species, whereas F-R and F-% had a positive logarithmic correlation with G(P) and D-E only under high-intensity, short-duration rainfall type. F-R and F-% were mainly affected by wind speed and the maximum 30-min rainfall intensity under low-intensity, long-duration rainfall type. At the intra-event scale, for both tree species, the mean lag time between the start of rainfall and stemflow was the shortest under high-intensity, short-duration rainfall type, while the mean duration and amount of stemflow after rain cessation were the greatest under high-amount, long-duration rainfall type. The relationship between stemflow intensity and rainfall intensity at the 5-min interval scale also depended greatly on rainfall type. These findings can help clarify stemflow dynamics and driving factors at both inter- and intra-event scales, and also provide abundant data and parameters for ecohydrological simulations in subtropical forests.

Automated summary

This study investigated the dynamics of stemflow at both inter- and intra-event scales in a subtropical deciduous forest, finding significant influences of tree species and rainfall type, with a more pronounced effect of tree species under low-intensity rainfall. Stemflow volume showed positive linear correlations with rainfall amount and event duration, while stemflow funnelling ratio and stemflow ratio had positive logarithmic correlations with these factors under high-intensity, short-duration rainfall. Wind speed and maximum 30-min rainfall intensity were identified as key factors affecting stemflow characteristics under low-intensity, long-duration rainfall.